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Acoustics
Number of Followers: 4  Open Access journalISSN (Online) 2624-599X Published by MDPI  [258 journals]
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- Acoustics, Vol. 7, Pages 2: Determining Water Pipe Leakage Using an RP-CNN
Model to Identify the Causes and Improve Poor-Accuracy Cases
Authors: Muhammad Anshari Caronge, Taichi Shibuya, Yasuhiro Arai, Xinyi Dong, Takaharu Kunizane, Akira Koizumi
First page: 2
Abstract: This study aimed to assess and improve the accuracy of a water leakage detection model proposed in preliminary research. The poor results for water leakage sound (recall) and background noise (specificity) were clarified using countermeasures in accordance with each condition. Additionally, frequency amplification in the range of 500–600 Hz, the attenuation of weak components, and a band-stop filter were used to remove the 50 Hz component and harmonics. Pre-processing was carried out in the form of amplification, with weak noise removed using a band-stop filter. The results showed that the application of the proposed model improved the detection accuracy by 80% at the observation points that initially had poor accuracy. Thus, the proposed method was effective at improving the performance of the Recurrence Plot-Convolutional Neural Network (RP-CNN) model for detecting water leakages.
Citation: Acoustics
PubDate: 2025-01-03
DOI: 10.3390/acoustics7010002
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 3: Effect of Acoustic Absorber Type and Size on
Sound Absorption of Porous Materials in a Full-Scale Reverberation Chamber
Authors: Oshoke Wil Ikpekha, Mark Simms
First page: 3
Abstract: The acoustic product development process, crucial for effective noise control, emphasises efficient testing and validation of materials for sound absorption in the R&D phase. Balancing cost-effectiveness, speed, and sustainability, the focus is on minimising excess materials. While strides have been made in reducing sample sizes for estimating random-incident absorption, challenges persist, particularly in establishing validity thresholds for smaller samples with increasing thickness, susceptible to potential overestimation due to edge effects. This study delves into analysing the absorption coefficients of widely used acoustic absorber types—polyester, fibreglass, and open-cell foam—in a full-scale reverberation chamber at Ventac, Blessington, and Wicklow. Demonstrating significant absorption above 500 Hz, these porous absorbers exhibit diminished effectiveness at lower frequencies. The strategic combination of these absorbers with different facings enhances their theoretical broadband absorption characteristics in practical applications. Moreover, the study assesses the validity threshold for reduced sample sizes, employing statistical analysis against ISO 354:2003 standard control samples of the absorber types. Analysis of Variance (ANOVA) on material groups underscores the significant influence of frequency components and sample sizes on the absorption coefficient. The determined validity threshold for 12.8 sqm ISO 354 standard control size is 7.7 sqm for the 25 mm open-cell foam. Similarly, the validity threshold of the 12 sqm ISO 354 standard control size is 9.6 sqm for the 20 mm 800 gsm polyester, 7.2 sqm for the 25 mm fibreglass, and the vinyl black on 25 mm fibreglass.
Citation: Acoustics
PubDate: 2025-01-07
DOI: 10.3390/acoustics7010003
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 4: Improved Direct–Parallel Active Noise
Control Systems for Narrowband Noise
Authors: Cheng-Yuan Chang, Ming-Han Ho, Sen M. Kuo
First page: 4
Abstract: Narrowband active noise control (NANC) systems are extensively used to cancel narrowband noise. Direct, parallel, and direct–parallel NANC systems use nonacoustic sensors to measure rotational speeds, and a bank of signal generators then produces synchronized sinusoidal waveforms as reference signals corresponding to the fundamental frequency of the undesired noise. The performance of direct NANC systems is based on the frequency difference between two adjacent reference input sinusoids. Parallel NANC systems apply several sinewave generators and two-weight adaptive filters in parallel to attenuate these narrowband components. Conventional direct–parallel NANC systems split these sinusoids into several mutually exclusive sets such that the distance between frequencies within sets is maximized. This paper proposes an improved direct–parallel NANC system in which reference sinusoidal signals are separated by amplitude to enhance efficiency and improve noise reduction performance. Several experiments were conducted using a muffler model to verify the performance of the proposed NANC system.
Citation: Acoustics
PubDate: 2025-01-13
DOI: 10.3390/acoustics7010004
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 5: A Periodic Extension to the Fokas Method for
Acoustic Scattering by an Infinite Grating
Authors: Shiza B. Naqvi, Lorna J. Ayton
First page: 5
Abstract: The Fokas method (also known as the unified transform method) is used to investigate acoustic scattering by thin, infinite grating by extending the methodology to apply to spatially periodic domains. Infinite grating is used to model a perforated screen, a material of interest in aeroacoustics and noise reduction. Once the method is established, its numerical results are verified against the Wiener–Hopf (WH) technique, which has solved the problem only for a special case. A key benefit of the novel approach is that the scatterer, modelled as an infinitely repeating unit cell consisting of a thin, rigid plate, can take any length. This is in contrast to the WH method, where the plate length is restricted to half the width of the unit cell (for this method, no such restriction exists). The numerical method is an over-sampled collocation method of the integral equation resulting from applying the Fokas method: the global relation. The only increase in complexity in adapting the Fokas method to more complicated cell geometries is a higher number of terms in the global relation. The proportion of energy transmitted and reflected by the grating structure is assessed for varying incident wave angles, frequencies, and plate lengths.
Citation: Acoustics
PubDate: 2025-01-17
DOI: 10.3390/acoustics7010005
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 6: Exploring Agreement in Voice Acoustic
Parameters: A Repeated Measures Case Study Across Varied Recording
Instruments, Speech Samples, and Daily Timeframes
Authors: Lady Catherine Cantor-Cutiva, Adrián Castillo-Allendes, Eric James Hunter
First page: 6
Abstract: Aims: The aim was to assess the agreement between microphone-derived and neck accelerometer-derived voice acoustic parameters and their associations with recording moments and speech types. Methods: Using simultaneous recordings, a 7-week study on a single individual was conducted to reduce intersubject variability. Agreement was assessed using Bland–Altman plots, and associations were examined with generalized estimating equations. Results: Bland–Altman plots showed no significant bias between microphone (MIC) and accelerometer (ACC) measurements for alpha ratio, CPP, PPE, SPL SD, fundamental frequency (fo) mean, and SD. Speech type and measurement timing were significantly associated with alpha ratio, while the instrument was not. Microphone measurements resulted in slightly lower CPP compared to the accelerometer, while reading samples yielded higher CPP compared to vowel productions. PPE, SPL SD, and fo mean showed significant associations with speech type, based on univariate analysis. Microphone measurements yielded a statistically smaller fo SD compared to the accelerometer, while reading productions had a larger fo SD than vowel productions. Conclusions: Fundamental frequency, alpha ratio, PPE, and SPL SD values were robust, regardless of the instrument used, suggesting the potential use of accelerometers in less-controlled environments. These findings are crucial for enhancing confidence in voice metrics and exploring efficient clinical assessment protocols.
Citation: Acoustics
PubDate: 2025-01-22
DOI: 10.3390/acoustics7010006
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 7: Quality Comparison of Dynamic Auditory
Virtual-Reality Simulation Approaches of Approaching Vehicles Regarding
Perceptual Behavior and Psychoacoustic Values
Authors: Jonas Krautwurm, Daniel Oberfeld-Twistel, Thirsa Huisman, Maria Mareen Maravich, Ercan Altinsoy
First page: 7
Abstract: Traffic safety experiments are often conducted in virtual environments in order to avoid dangerous situations and conduct the experiments more cost-efficiently. This means that attention must be paid to the fidelity of the traffic scenario reproduction, because the pedestrians’ judgments have to be close to reality. To understand behavior in relation to the prevailing audio rendering systems better, a listening test was conducted which focused on perceptual differences between simulation and playback methods. Six vehicle driving-by-scenes were presented using two different simulation methods and three different playback methods, and binaural recordings from the test track acquired during the recordings of the vehicle sound sources for the simulation were additionally incorporated. Each vehicle driving-by-scene was characterized by different vehicle types and different speeds. Participants rated six attributes of the perceptual dimensions: “timbral balance”, “naturalness”, “room-related”, “source localization”, “loudness” and “speed perception”. While the ratings showed a high degree of similarity among the ratings of the sound attributes in the different reproduction systems, there were minor differences in the speed and loudness estimations and the different perceptions of brightness stood out. A comparison of the loudness ratings in the scenes featuring electric and combustion-engine vehicles highlights the issue of reduced detection abilities with regard to the former.
Citation: Acoustics
PubDate: 2025-02-08
DOI: 10.3390/acoustics7010007
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 8: Effects of Acoustic Shielding on Beamforming
for Rotating Sound Source Localization
Authors: Ce Zhang, Cheng Wei Lee, Wei Ma
First page: 8
Abstract: Beamforming for rotating sound source localization (denoted by rotating beamforming) is widely used in engineering nowadays. Acoustic shielding, such as shafts and covers, is typically employed in the practical measurement of rotating source localization. Acoustic shielding blocks the signal propagation between rotating sources and the array, and thus affects the performance of rotating beamforming. However, the detailed effects of acoustic shielding on rotating beamforming are still unclear. In this study, the blocking rate that represents the degree of signal propagation path blockage is defined first. The effects of acoustic shielding on rotating beamforming are then investigated in simulations. Finally, these effects are verified by experiments. According to the results of the simulation and experiments, rotating beamforming can still localize rotating sources, as long as the signal propagation path is not completely blocked. However acoustic shielding decreases sound intensity accuracy, especially when the blocking rate is larger than 50%. When acoustic shielding is employed, the ability of rotating beamforming to compensate for Doppler effects weakens.
Citation: Acoustics
PubDate: 2025-02-24
DOI: 10.3390/acoustics7010008
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 9: Identification of the Aeroacoustic Emission
Source Regions Within a Ceiling Swirl Diffuser
Authors: Philipp Ostmann, Martin Kremer, Dirk Müller
First page: 9
Abstract: The acoustic emissions of ventilation systems and their subcomponents contribute to the perceived overall comfort in indoor environments and are, therefore, the subject of research. In contrast to fans, there is little research on the aeroacoustic properties of air diffusers (often referred to as outlets). This study investigates a commercially available ceiling swirl diffuser. Using a hybrid approach, a detailed three-dimensional large-eddy simulation is coupled with a perturbed wave equation to capture the aeroacoustic processes within the diffuser. The flow model is validated for the investigated operating point of 470 m3/h using laser-optical and acoustic measurements. To identify the noise sources, the acoustic pressure is sampled with various receivers and on cut sections to evaluate the cross-power spectral density, and the sound-pressure level distribution on cut sections is evaluated. It is found that the plenum attenuates the noise near its acoustic eigenmodes and thus dominates other noise sources by several orders of magnitude. By implementing the plenum walls as sound-absorbing, the overall sound-pressure level is predicted to decrease by nearly 10 dB/Hz. Other relevant geometric features are the mounting beam and the guide elements, which are responsible for flow-borne noise emissions near 698 Hz and 2699 Hz, respectively.
Citation: Acoustics
PubDate: 2025-02-24
DOI: 10.3390/acoustics7010009
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 10: Characterization and Effects of Floor Impact
Sound in Residential Buildings: A Systematic Review
Authors: Yuying Zou, Mengjin Liu, Hui Ma
First page: 10
Abstract: The lightweight development trend of modern residential structures reduces sound attenuation in buildings and makes sound propagation paths more complex. Neighbor-induced impact sound has become a significant source of residents’ dissatisfaction with the acoustic environment. To gain a deeper understanding of the characteristics of residential impact sound, reduce its impact on users, and improve the quality of residential buildings, a systematic review of existing research based on PRISMA2020 was carried out. Articles indexed in the Web of Science core dataset and Scopus were searched, with a cutoff date of October 2024. After screening and reviewing, 132 articles were systematically analyzed, categorizing the research on floor impact sound into four aspects, namely impact sound sources, evaluation indicators, prediction methods, and improvement measures. The results show that due to the diversity of real sound sources and differences in living habits, the standard impact sound sources in different countries or regions still need further study. Both subjective and objective evaluations indicate that heavyweight impact sound, particularly low-frequency sound, has the greatest impact on occupants and is the most difficult to eliminate. The physical characteristics of floor impact sound can be predicted using methods such as finite element analysis. However, there are fewer prediction methods for subjective evaluations due to the poor correlation between subjective and objective evaluation indicators. Though different soundproofing measures significantly improve the sound insulation of impact sound, they are still not widely applied due to materials, construction techniques, and time and economic costs. This study provides a reference for research on residential impact sound in China and offers an outlook for future research directions.
Citation: Acoustics
PubDate: 2025-02-28
DOI: 10.3390/acoustics7010010
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 11: Evaluation of Soundboard Damping Variations
on Physical and Perceptual Aspects of the Sound of a Steel-String Acoustic
Guitar
Authors: Tom Wühle, Sebastian Merchel, M. Ercan Altinsoy
First page: 11
Abstract: To make guitars with high sonic quality, it is essential to understand the relationship between the physical characteristics of the selected materials and the acoustic characteristics of the final instrument and how they will be perceived. The selection of wood for the soundboard is a crucial step in the guitar-making process. One relevant physical characteristic is internal material damping, about which, however, only little is known in comparison to other characteristics such as density and Young’s modulus. The present study investigated the relationship of soundboard damping to both physical and perceptual aspects of guitar sound. Three similar steel-string guitars were built with the damping of their soundboards varying between low, mid and high. Measurements of the transfer function and the plucked tone decay of the final guitars were carried out. A listening test and a playing test were conducted. The participants were asked to rate preference and seven sound attributes comprising loudness and both spectral and temporal aspects. To prepare the listening test, a short sequence was recorded by a professional guitarist with each guitar. The results suggest that varying soundboard damping had no practically relevant influence on the physical and perceptual aspects of the sound of the guitar used in this study.
Citation: Acoustics
PubDate: 2025-02-28
DOI: 10.3390/acoustics7010011
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 12: Layered Acoustic Structures with Equally
Phased Elements
Authors: Paola Gori, Claudia Guattari, Luca Evangelisti, Roberto De Lieto Vollaro, Francesco Asdrubali
First page: 12
Abstract: It is often required to control the acoustic transmission across layered structures in order to favor or, more frequently, limit it in prescribed energy ranges. The selection of the materials and layer thicknesses needed to achieve a given objective is not straightforward, and it is often performed empirically. This is connected with the lack of simple models that dictate the frequency behavior of the layered structure. In this work, we present an approach to the systematic design of layered media, based on an assumption that allows us to obtain simple analytical expressions for the occurrence of bandgaps in the frequency response of ideally infinite periodic structures. Correspondingly low-transmission frequency ranges are then analyzed and discussed in finite-thickness realizations of the designed periodic structures.
Citation: Acoustics
PubDate: 2025-03-04
DOI: 10.3390/acoustics7010012
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 13: Vocal Directivity of the Greek Singing Voice
on the First Three Formant Frequencies
Authors: Georgios Dedousis, Konstantinos Bakogiannis, Areti Andreopoulou, Anastasia Georgaki
First page: 13
Abstract: This study explores the relationship between formant frequencies and the directivity patterns of the Greek singing voice. Recordings were conducted in a controlled acoustic environment with four professional singers, two trained in classical music and two in Byzantine chant. Using microphones placed symmetrically on a hemispherical structure, participants sang the Greek vowels across different registers. Directivity patterns were analyzed in third-octave bands centered on each singer’s first three formant frequencies (F1, F2, F3). The results indicate that directivity patterns vary with register and center frequency, with differences observed across vowels and singers. These findings contribute to vocal production research and the development of simulation, auralization, and virtual reality applications for speech and music.
Citation: Acoustics
PubDate: 2025-03-04
DOI: 10.3390/acoustics7010013
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 14: From Spherical Harmonics to Gaussian
Beampatterns
Authors: Kevin J. Parker, Miguel A. Alonso
First page: 14
Abstract: The use of multipoles, otherwise called spherical wavefunctions, has been explored for acoustic fields that can be omnidirectional, for example, in scattering theory. Less developed is the use of spherical harmonic multipoles for the construction of directed beams, such as the Gaussian unfocused beampattern, which is an important reference beam in many practical applications. We develop the straightforward construction of a Gaussian unfocused beam using the special properties of the sum of spherical harmonics; these include the use of an imaginary offset in directing the forward propagation to the desired beampattern. Examples are given for narrowband and broadband pulse propagation in the ultrasound MHz range, with comparisons against a classical acoustics formulation of the Gaussian beam. The use of spherical harmonics forms an alternative framework for devising beampatterns, with apodization and concentration issues of the beam linked to an array of a limited number of discrete multipoles at the source.
Citation: Acoustics
PubDate: 2025-03-11
DOI: 10.3390/acoustics7010014
Issue No: Vol. 7, No. 1 (2025)
- Acoustics, Vol. 7, Pages 1: Influence of Infotainment-System Audio Cues on
the Sound Quality Perception Onboard Electric Vehicles in the Presence of
Air-Conditioning Noise
Authors: Massimiliano Masullo, Katsuya Yamauchi, Minori Dan, Federico Cioffi, Luigi Maffei
First page: 1
Abstract: Car cabin noise generated by heating, ventilation, and air-conditioning (HVAC) systems significantly impacts passengers’ acoustic comfort. In fact, with the reduction in engine noise due to the passage from internal combustion to electric or hybrid-electric engines, interior background noise has dramatically reduced, especially at 25% and 50% HVAC airflow rates. While previous research has focused on the effect of HVAC noise in car cabins, this paper investigates the possibility of using car infotainment-system audio cues to moderate onboard sound quality perception. A laboratory experiment combining the factors of infotainment-system audio (ISA) cues, signal-to-noise ratios (SNRs), and airflow rates (AFRs) at different levels was performed in two university laboratories in Italy and Japan involving groups of local individuals. The results indicate that introducing ISA cues in car cabins fosters improvements in the perceived aesthetic dimension of sound quality, making it more functioning, natural, and pleasant. For the Italian group, adding ISA cues also moderated the loudness dimension by reducing noise perception. The moderating effects of ISA cues differed between the Italian and Japanese groups, depending on the AFR. All these effects were more evident at the SNR level of −4 dB when the ISA cues competed with existing background noise.
Citation: Acoustics
PubDate: 2024-12-25
DOI: 10.3390/acoustics7010001
Issue No: Vol. 7, No. 1 (2024)
- Acoustics, Vol. 6, Pages 805-817: Non-Monotonic Variation of Acoustic
Spectrum with the Mass or Thickness of a Layered Structure
Authors: Sergiu Cojocaru
First page: 805
Abstract: We are examining the behavior of resonance frequencies and their response to variations of material parameters such as thicknesses, masses, and bulk velocities for certain Rayleigh–Lamb acoustic modes in a multilayered structure. The treatment is based on recent explicit analytic solutions that have allowed us to explore the entire parametric space using dimensionless ratios. This exploration has revealed a complex parametric dependence of the phase velocities and their mass loading response. Specifically, for the fundamental flexural modes in a bilayer, we have shown that both quantities change in a strongly non-monotonic way with thickness, density, or bulk velocity ratios. Even in the regime of thin coating, commonly encountered in acoustic sensing applications, we have found important differences from previously known results, e.g., that response to loading may switch its sign multiple times when the velocity of the deposited material is increased. We have also discovered that the fundamental dilatational modes can be highly effective in stabilizing resonant frequencies against even large variations of the thickness or mass of the exposed layer. This property is demonstrated in an explicit form by the derived expression for the mass coefficient of frequency for an arbitrary number of layers.
Citation: Acoustics
PubDate: 2024-09-24
DOI: 10.3390/acoustics6040045
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 818-833: Theoretical and Experimental Assessment
of Nonlinear Acoustic Effects through an Orifice
Authors: Elio Di Giulio, Riccardo Di Leva, Raffaele Dragonetti
First page: 818
Abstract: Nonlinear acoustic effects become prominent when acoustic waves propagate through an orifice, particularly at higher pressure amplitudes, potentially generating vortex rings and transferring acoustic energy into the flow. This study develops and validates a predictive theoretical model for acoustic behaviour both within and outside an orifice under linear conditions. Using transfer matrices, the model predicts the external acoustic field, while finite element numerical simulations are employed to validate the theoretical predictions in the linear regime. The experimental setup includes an impedance tube with a plate and orifice, supported by a custom-built system, where a loudspeaker generates acoustic waves. A single microphone is used to measure acoustic particle velocity and characterize the phenomenon, enabling the identification of the onset of nonlinearity. The experimental data show good agreement with the linear theoretical predictions. This work represents the first observation of nonlinear effects in a free-field environment within a semi-anechoic chamber, eliminating reflections from external surfaces, and demonstrates the efficacy of a purely acoustic-based system (speaker and two microphones) for evaluating speaker velocity and the resulting velocity within the orifice.
Citation: Acoustics
PubDate: 2024-09-30
DOI: 10.3390/acoustics6040046
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 834-869: Acoustic Emission Characteristics of
Galling Behavior from Dry Scratch Tests at Slow Sliding Speed
Authors: Timothy M. Devenport, Ping Lu, Bernard F. Rolfe, Michael P. Pereira, James M. Griffin
First page: 834
Abstract: Galling wear, a severe form of wear, is a known problem in sheet metal forming. As the wear state is not directly observable in closed tribosystems, such as in industrial sheet metal forming processes, indirect tool wear monitoring techniques for inferring the wear state of the tool from suitable signal characteristics are the subject of intense research. The analysis of acoustic emissions is a promising technique for tool condition monitoring. This research has explored feature selection using t-tests, linear regression models, and cluster analysis of the data. This analysis has been conducted both with and without the inclusion of control variables, friction, and roughness to discriminate between the behavior of the acoustic emissions during different stages of galling wear. Scratch testing at slow sliding speed (1 mm/s) has been used to produce the galling wear between a tool steel indenter and aluminum sheet at 10 N applied load, for which the acoustic emissions were recorded. The bursts of the acoustic emission signal were processed and investigated to observe how the bursts changed with increasing galling damage (increasing material removal and transfer). Novel parameters in the field of galling wear have been identified, and novel models for observing the change in galling wear have been identified, thus furthering the development of acoustic emissions analysis as a non-invasive condition monitoring system, particularly for sheet metal forming processes.
Citation: Acoustics
PubDate: 2024-10-04
DOI: 10.3390/acoustics6040047
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 870-884: Underwater Small Target Detection Method
Based on the Short-Time Fourier Transform and the Improved Permutation
Entropy
Authors: Jing Zhou, Baoan Hao, Yaan Li, Xiangfeng Yang
First page: 870
Abstract: In the realm of underwater active target detection, the presence of reverberation is an important factor that significantly impacts the efficacy of detection. This article introduces the improved permutation entropy algorithm into the analysis of active underwater acoustic signals. Based on the significant difference between the improved permutation entropy in the frequency domain and the time domain, a frequency-domain-improved permutation entropy detection algorithm is proposed. The performance of this algorithm and the energy detection algorithm are compared and analyzed under the same conditions. The results show that the spectral entropy detector is about 2.7 dB better than the energy detector, realized via active small target signal detection under a reverberation background. At the same time, based on the characteristics of improved permutation entropy changing with the length of processed data, the short-time Fourier transform is integrated into frequency domain entropy detection to obtain distance and velocity information of the target. To validate the proposed methods, comparative analysis experiments were executed utilizing actual experiment data. The outcomes of both simulation and actual experiment data processing demonstrated that the sliding entropy feature detection method for signal spectrum has a small computational complexity and can quickly determine whether there is a target echo in the receive data. The two-dimensional entropy feature detection method for short-time signal spectra was found to effectively mitigate the impact of reverberation intensity and while enhancing the prominence of the target signal, thereby yielding a more robust detection outcome.
Citation: Acoustics
PubDate: 2024-10-10
DOI: 10.3390/acoustics6040048
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 885-886: Correction: Coppieters de Gibson, L.;
Garner, P.N. Training a Filter-Based Model of the Cochlea in the Context
of Pre-Trained Acoustic Models. Acoustics 2024, 6, 470–488
Authors: Louise Coppieters de Gibson, Philip N. Garner
First page: 885
Abstract: The authors would like to make the following corrections to the original publication [...]
Citation: Acoustics
PubDate: 2024-10-12
DOI: 10.3390/acoustics6040049
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 887-910: The Adjusting Effects of Trees on
Cfa-Climate Campus Acoustic Environments and Thermal Comforts in the
Summer
Authors: Wen Lu, Yanyi Chen, Tianru Zhou, Jian Zhang, Aoyan Xiao, Feng Zhu, Hui Yin, Ting Liu
First page: 887
Abstract: This study explores the effects of trees on the acoustic and thermal environment in addition to people’s responses to trees in different contexts. Through field measurements conducted during the summer of 2023 at the campus of the Southwest University of Science and Technology in Mianyang, residents’ neutral points were locally found to be 52.2 dBA (acoustic) and 23.8 °C (thermal). Further, at their maximum, the trees were able to reduce heat stress by 4 °C (indicated by the physiologically equivalent temperature—PET) and the noise level by 10 dBA (indicated by the A-weighted sound pressure—LAeq); this was achieved by trees with a crown diameter of 20 m. Subjective acoustic and thermal responses varied depending on the context. Acoustically, their neutral LAeq values toward the sounds of traffic, teaching, sports, and daily life were 46.9, 52.5, 51.0, and 52.7 dBA, respectively. Thermally, pedestrians’ neutral PET values were 24.2, 26.1, 22.3, and 25.1 °C, respectively, under the same conditions. These phenomena might be a consequence of the effects of sound frequencies. Future urban forestry research should focus on planting for environmental quality improvement.
Citation: Acoustics
PubDate: 2024-10-16
DOI: 10.3390/acoustics6040050
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 911-932: Acoustics in Baroque Catholic Church
Spaces
Authors: Enedina Alberdi, Miguel Galindo, Angel L. León-Rodríguez, Jesús León
First page: 911
Abstract: After the Council of Trent (1545–1563), the Catholic Church undertook a profound renovation, which affected the spatial configuration of the churches to adjust to the spirit of the Counter-Reformation. The acoustic cultural heritage in these spaces have been studied by different researchers, proposing the joint analysis of 66 Catholic churches from the Baroque period. This study delves into the global characterisation of the sample and establishes correlations between geometric and acoustic parameters. From the acoustic analysis, it is clear that the central floor typology, as opposed to Latin cross churches, presents better average values of musical clarity in relation to their volume. The analysis of the relationship between acoustic and geometric parameters, when the sample of churches is discriminated by typology, allows for the establishment of appropriate correlations for Latin cross floor plans, single naves and basilicas, but not when the analysis is carried out for the entire sample. These correlations are a tool that allows us to evaluate acoustic parameters not measured in situ in Catholic churches of the Baroque period in a predictive way as a function of other measured acoustic or geometric parameters.
Citation: Acoustics
PubDate: 2024-10-30
DOI: 10.3390/acoustics6040051
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 933-965: Real and Virtual Lecture Rooms:
Validation of a Virtual Reality System for the Perceptual Assessment of
Room Acoustical Quality
Authors: Angela Guastamacchia, Riccardo Giovanni Rosso, Giuseppina Emma Puglisi, Fabrizio Riente, Louena Shtrepi, Arianna Astolfi
First page: 933
Abstract: Enhancing the acoustical quality in learning environments is necessary, especially for hearing aid (HA) users. When in-field evaluations cannot be performed, virtual reality (VR) can be adopted for acoustical quality assessments of existing and new buildings, contributing to the acquisition of subjective impressions in lab settings. To ensure an accurate spatial reproduction of the sound field in VR for HA users, multi-speaker-based systems can be employed to auralize a given environment. However, most systems require a lot of effort due to cost, size, and construction. This work deals with the validation of a VR-system based on a 16-speaker-array synced with a VR headset, arranged to be easily replicated in small non-anechoic spaces and suitable for HA users. Both objective and subjective validations are performed against a real university lecture room of 800 m3 and with 2.3 s of reverberation time at mid-frequencies. Comparisons of binaural and monoaural room acoustic parameters are performed between measurements in the real lecture room and its lab reproduction. To validate the audiovisual experience, 32 normal-hearing subjects were administered the Igroup Presence Questionnaire (IPQ) on the overall sense of perceived presence. The outcomes confirm that the system is a promising and feasible tool to predict the perceived acoustical quality of a room.
Citation: Acoustics
PubDate: 2024-10-30
DOI: 10.3390/acoustics6040052
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 966-977: Seafloor Topographic Data Processing in
Near-Seafloor Acoustic Field Simulation
Authors: Siyu Ma, Yuxiang Zhang, Zhinan Xie, Jun Li
First page: 966
Abstract: Near-seafloor acoustic field characteristics are essential prior knowledge for near-seafloor underwater acoustic engineering. Scholte waves are a crucial component of the near-seafloor acoustic fields. These fields, when considering Scholte waves, are susceptible to seafloor relief. However, open-source bathymetric datasets generally lack sufficient precision. Therefore, acoustic field simulations using open-source data can contain significant errors or even introduce erroneous propagation characteristics. The spectral element method (SEM) is an example of exploring the influence of an inadequate spatial-sampling rate and sea-depth precision on acoustic field simulations. In this article, appropriate methods for topographic processing are presented. The results indicate that the terrain can be corrected using cubic spline interpolation in cases of an inadequate spatial-sampling rate. Where there is insufficient sea-depth precision, this study proposes a terrain processing method. The first step involves sequentially determining the interpolation points for the rising and falling edge, depressions, bulges, and horizontal segments. Then, it adopts cubic spline interpolation. The SEM examples effectively verify this effect. Given the limited research on terrain correction in acoustic field simulations, this study introduces a low-complexity method that can effectively support exploring acoustic fields affected by seafloor terrain.
Citation: Acoustics
PubDate: 2024-10-31
DOI: 10.3390/acoustics6040053
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 978-996: Development and Assessment of a
Miniaturized Test Rig for Evaluating Noise Reduction in Serrated Blades
Under Turbulent Flow Conditions
Authors: Andrei-George Totu, Cristian-Teodor Olariu, Andrei-Tudor Trifu, Andreea-Cătălina Totu, Grigore Cican
First page: 978
Abstract: The implementation of serrated stator blades in axial compressor and fan stages offers significant advantages, such as enhanced performance and reduced noise levels, making it a practical and cost-effective solution. This study explores the impact of serrated blade design on noise reduction under specific engine operating conditions. A small-scale experimental test setup with a turbulence-inducing grid was designed for testing multiple grid sizes in order to identify the most promising configuration which replicates rotor–stator interaction. Numerical simulations and early experimental tests in an anechoic chamber using a four-blade cascade configuration at an airflow speed of 50 m/s revealed a small but notable noise reduction in the 1–6 kHz range for a partially matched grid–blade geometry. Serrated blades demonstrated an overall sound pressure level reduction of 1.5 dB and up to 12 dB in tonal noise, highlighting the potential of cascade configurations to improve acoustic performance in gas turbine applications.
Citation: Acoustics
PubDate: 2024-11-11
DOI: 10.3390/acoustics6040054
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 997-1020: A Review and Bibliometric Analysis of
Unmanned Aerial System (UAS) Noise Studies Between 2015 and 2024
Authors: Chuyang Yang, Ryan J. Wallace, Chenyu Huang
First page: 997
Abstract: Unmanned aerial systems (UAS), commonly known as drones, have gained widespread use due to their affordability and versatility across various domains, including military, commercial, and recreational sectors. Applications such as remote sensing, aerial imaging, agriculture, firefighting, search and rescue, infrastructure inspection, and public safety have extensively adopted this technology. However, environmental impacts, particularly noise, have raised concerns among the public and local communities. Unlike traditional crewed aircraft, drones typically operate in low-altitude airspace (below 400 feet or 122 m), making their noise impact more significant when they are closer to houses, people, and livestock. Numerous studies have explored methods for monitoring, assessing, and predicting the noise footprint of drones. This study employs a bibliometric analysis of relevant scholarly works in the Web of Science Core Collection, published from 2015 to 2024, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) data collection and screening procedures. The International Journal of Environmental Research and Public Health, Aerospace Science and Technology, and the Journal of the Acoustical Society of America are the top three preferred outlets for publications in this area. This review unveils trends, topics, key authors and institutions, and national contributions in the field through co-authorship analysis, co-citation analysis, and other statistical methods. By addressing the identified challenges, leveraging emerging technologies, and fostering collaborations, the field can move towards more effective noise abatement strategies, ultimately contributing to the broader acceptance and sustainable integration of UASs into various aspects of society.
Citation: Acoustics
PubDate: 2024-11-20
DOI: 10.3390/acoustics6040055
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1021-1046: A Design Methodology Incorporating a
Sound Insulation Prediction Model, Life Cycle Assessment (LCA), and
Thermal Insulation: A Comparative Study of Various Cross-Laminated Timber
(CLT) and Ribbed CLT-Based Floor Assemblies
Authors: Mohamad Bader Eddin, Sylvain Ménard, Bertrand Laratte, Tingting Vogt Wu
First page: 1021
Abstract: Mass timber is increasingly being employed in constructing low- and mid-rise buildings. One of the primary reasons for using mass timber structures is their sustainability and ability to reduce environmental consequences in the building sector. One criticism of these structures is their lower subjective sound insulation quality. Therefore, acoustic treatments should be considered. However, acoustic solutions do not necessarily contribute to lower environmental impacts or improved thermal insulation performance. This paper discusses a design methodology that incorporates the development of a sound insulation prediction tool (using an artificial neural networks approach), life cycle assessment analysis, and thermal insulation study. A total of 112 sound insulation measurements (in one-third octave bands from 50 to 5000 Hz) are utilized to develop the network model and are also used for the LCA and thermal insulation study. They are lab-based measurements and are performed on 45 various CLT- and ribbed CLT-based assemblies. The acoustic model demonstrates satisfactory results with 1 dB differences in the prediction of airborne and impact sound indices (Rw and Ln,w). An acoustic sensitivity study and a statistical analysis are then conducted to validate the model’s results. Additionally, an LCA analysis is performed on the floor assemblies to calculate their environmental footprints. LCA categories are plotted against the acoustic performance of floors. No correlations are found, and the results emphasize that a wide range of sound insulation can be achieved with similar environmental impacts. Within each acoustic performance tier, the LCA results can be optimized for a floor assembly by selecting appropriate materials. The thermal insulation of floors is then calculated. Overall, a strong positive correlation is found between the total thermal resistance and heat loss against acoustic performance. Designers should be cognizant of the trade-offs between acoustic, thermal insulation, and environmental performance when choosing assemblies with favorable environmental impacts relative to acoustic and thermal insulation ratios.
Citation: Acoustics
PubDate: 2024-11-25
DOI: 10.3390/acoustics6040056
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1047-1073: Longitudinal Effect of Music Exposure
on Hearing Among Vocal Performance Students
Authors: Rachel L. Lowrance, Charles J. Nudelman, Yvonne Gonzales Redman, Pasquale Bottalico
First page: 1047
Abstract: The effects of music exposure on vocal performers remain relatively unknown. This study aimed to assess the immediate and long-term effects of music and singing practice on the peripheral auditory system of vocal performers using otoscopy, pure-tone audiometry, and noise dosimetry. The hearing status, sound pressure levels (SPLs), and sound doses of 12 vocal performers with normal hearing at the study’s onset were evaluated. Pre- and post-study questionnaires regarding the participants’ otologic health and music-making activities, as well as repeated hearing evaluations, were implemented. Additionally, noise dosimetry was conducted on each participant’s most vocally active day of the week. Audiometric assessments generally revealed normal hearing thresholds, with some exceptions. Half of the participants exhibited elevated low-frequency thresholds and over half of the participants displayed emerging audiometric “notches” at 6000 Hz. Noise dosimetry measurements indicated that most of the participants were consistently exposed to SPLs during music-making activities that exceeded recommended limits. Questionnaire responses highlighted that the participants often engaged in extra-curricular music-making activities, frequently with piano accompaniment, and with little to no use of hearing protection devices. A few of the participants reported histories of otologic issues and potential hearing problems.
Citation: Acoustics
PubDate: 2024-11-25
DOI: 10.3390/acoustics6040057
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1074-1087: Porous Metal Backing for
High-Temperature Ultrasonic Transducers
Authors: Guy Feuillard, Dang Chi Nguyen, Marc Lethiecq, Mathieu Jean, Frédéric Navacchia
First page: 1074
Abstract: Improving the performance of high-temperature ultrasonic transducers is a goal of major importance in many industrial applications. To this aim, we propose to use porous metals that support high temperatures as backings. Thus, the acoustic properties of stainless steel and porous stainless steel with porosity of 25% and 35% are determined at ambient temperature and up to 400 °C. Over the temperature range, the longitudinal wave velocity variation is comprised between 5% and 6% in the porous metals. We find that temperature does not significantly affect the attenuation in the material. The pulse-echo response and frequency response of a LiNbO3-based transducer with a porous backing are simulated using a one dimensional electroacoustic model. These simulations, compared to those of a reference transducer, show that the axial resolution with such a design allows these transducers to be used for imaging and/or Non-Destructive Testing and evaluation at high temperature.
Citation: Acoustics
PubDate: 2024-11-25
DOI: 10.3390/acoustics6040058
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1088-1099: Cellulose-Based Acoustic Absorber with
Macro-Controlled Properties
Authors: Jérôme Lefebvre, Benoit Genestie, Alexandre Leblanc
First page: 1088
Abstract: Cellulose-based materials are now commonly used, including in the field of acoustic comfort. Often presented as a less environmentally impactful alternative to traditional acoustic absorbents (such as melamine, glass wool, etc.), these cellulose-based materials are more frequently derived from recycling, undergoing, in most cases, a technical process that allows these cellulose fibers to be obtained, thus inheriting the acoustic properties of the latter, with limited or even non-existent control. This paper proposes a manufacturing process that allows for the production of cellulose foam with precise control over its porosity, pore size, and interconnections. In addition to exhibiting good sound absorption properties, this process also enables the fabrication of gradient-porous structures and other hybrid materials, which can result in remarkable sound absorption properties.
Citation: Acoustics
PubDate: 2024-11-28
DOI: 10.3390/acoustics6040059
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1100-1114: Convergence Time Measurement Method of
Active Noise Cancelling Headphones
Authors: Agata Zatorska, Michał Łuczyński, Wojciech Bartnik
First page: 1100
Abstract: The aim of this paper is to develop and describe an objective method for measuring the performance of headphones with active noise cancellation (ANC). The focus was on measuring both passive and active sound attenuation and determining the convergence time of the ANC system. A new parameter was introduced—the reaction speed, expressed in dB/ms, allowing an accurate correlation of the active attenuation values with the time needed to achieve them. A series of tests were conducted using three active noise cancelling headphone models of different prices and specifications. The response times were recorded and analyzed. Measurements were performed on two different dummy head models and under two different measurement conditions (reverberation chamber and acoustically adapted room). The results revealed differences between the models, with some headphones consistently providing a better reaction speed. Remarkably, the headphone associated with the lower reaction speed were also the cheapest. This justifies the need for the reaction speed to be a parameter provided by the manufacturer in the datasheet.
Citation: Acoustics
PubDate: 2024-11-30
DOI: 10.3390/acoustics6040060
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1115-1139: Acoustical Traditions and Cultural
Identity: Exploring Kunqu’s Contribution to Collective Memory
Authors: Zihan Ding, Francesco Aletta
First page: 1115
Abstract: Kunqu Opera, hailed as the “ancestor of all Chinese operas”, plays a crucial role in preserving cultural identity and collective memory in the Jiangnan region. This research examines the acoustical traditions of Kunqu. Through expert interviews and thematic analysis, the study explores key acoustic elements, including vocal techniques and musical structures, and their symbolic and emotional impact. Five central themes emerged, including Kunqu’s role in collective memory, its function as a cultural symbol, the evolution of its transmission, the emotional resonance of its acoustic elements, and the modern challenges and opportunities for preservation. The findings highlight the importance of maintaining Kunqu’s cultural identity within acoustical heritage, while also recognizing the need for innovation in its transmission. This research contributes to the broader discussion on intangible cultural heritage and provides insights into how traditional art forms like Kunqu can be preserved amidst modernization.
Citation: Acoustics
PubDate: 2024-12-04
DOI: 10.3390/acoustics6040061
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1140-1153: Analysis of the Effectiveness of
Multifrequency OFDM Systems with a Constant Envelope in a Hydroacoustic
Simulator and During In Situ Tests
Authors: A. Yu. Rodionov, L. G. Statsenko, A. A. Chusov, D. A. Kuzin, M. M. Smirnova
First page: 1140
Abstract: The key elements in the operation of modern underwater robotic systems are hydroacoustic communication and navigation systems. Hydroacoustic data transmission channels are designed in such a way that the transmitted information signals must be resistant to various types of interference and distortion, even without preliminary estimates of the channel parameters, due to their significant non-stationarity because of the roughness of the sea surface, currents, and the movement of underwater vehicles. Furthermore, due to the high mobility of underwater vehicles, the transmission time of navigation signals and necessary information packets must be significantly reduced, which can negatively affect the noise immunity of the packages. For these purposes, digital wideband signals and orthogonal frequency division multiplexing (OFDM) are widely used; however, a number of significant drawbacks of these types of modulations often do not allow for the forming of a reliable channel for transmitting information, and for the navigation of mobile underwater systems. Unfortunately, this problem is not comprehensively presented in the literature. The authors propose to use the algorithm of digital data transmission based on the OFDM constant envelope multifrequency modulation (CE-OFDM) with differential symbol coding, which is suitable for non-stationary hydroacoustic environments. The presented algorithm, due to the minimization of the signal peak factor, can improve the signal-to-noise ratio at the receiving end by 5–10 dB, with a number of other advantages, over the classical OFDM method. The authors also numerically found groups of short binary sequences from 14–55 elements long, with the best autocorrelation properties for the formation of synchronization and navigation preambles with high noise immunity to Doppler and multipath effects that are characteristic of the hydroacoustic communication channel. The proposed algorithms were tested on the certain channel models on the Watermark acoustic simulator, as well as in shallow water at distances up to 2 km.
Citation: Acoustics
PubDate: 2024-12-12
DOI: 10.3390/acoustics6040062
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1154-1179: Introducing Silencers on Micro
Turboshafts Powering Unmanned Aerial Vehicles
Authors: Andrei-George Totu, Cristian Olariu, Marius Deaconu, Laurențiu Cristea, Luminița Drăgășanu, Constantin Sandu
First page: 1154
Abstract: The transition to alternative electrical energy solutions for drone propulsion systems presents several challenges, particularly in managing noise. This noise, compounded by that from the propellers, can produce spectra that are either unpleasant to humans or detrimental to mission objectives. This study explores potential solutions to mitigate noise produced by a micro turboshaft engine, focusing on the solutions’ impact on weight, power output, and acoustic level. We propose two modular, scalable designs—one for the intake and one for the exhaust—based on well-known applications in cold and hot flows. These designs aim to operate effectively across the audible frequency spectrum and incorporate various Helmholtz resonator geometries, including combinations of different lengths, perforated metal sheet parameters, and cavity-filling materials, to enhance bandwidth and noise reduction. Experimental results indicate that these designs can achieve tonal noise reductions of up to 40 dB. While the results are promising, further analysis is required to evaluate the practical applicability and comprehensive impact of these solutions on drone performance.
Citation: Acoustics
PubDate: 2024-12-16
DOI: 10.3390/acoustics6040063
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 1180-1192: Racing in Kart Dromes: Laboratory and
Site Assessment of Noise Levels from Competition and Rental Karts
Authors: Antonella Bevilacqua, Gino Iannace, Luis Gomez-Agustina, Amelia Trematerra
First page: 1180
Abstract: Kart racing is one of the hobbies that people get passionate about from a young age. Kart dromes are commonly built in suburban or rural areas, generally surrounded by industrial zones and sporadic residential buildings. The circuits are primarily active during summer, hosting races that often extend into the evening and night hours, where each race has a duration of 20 min. This study examines the noise generated by kart dromes through acoustic measurements conducted at a kart drome located in southern Italy, where a microphone was placed at the side of the circuit for short periods in addition to a survey conducted at the nearest sensitive receptor. Another survey was conducted within the kart drome for a long-term period to record all of the variations in noise levels of a typical summer day when the races are organized during the nighttime; for this type of data, the hourly average values were taken for one week in June, July, and August, highlighting the increasing trend in the noise levels due to the kart races. However, a detailed analysis of noise emissions during different phases of kart operation revealed two significant acoustic events, such as the acceleration of pass-by peaks centered on high frequencies and strong breaking noise at curves that are centered at low-medium frequencies, causing a whistling noise of the wheels while turning the kart. This paper highlights the increasing trend in noise levels during summer nighttime races, compares on-site measurements with laboratory data, and discusses the implications for local communities and noise regulations.
Citation: Acoustics
PubDate: 2024-12-17
DOI: 10.3390/acoustics6040064
Issue No: Vol. 6, No. 4 (2024)
- Acoustics, Vol. 6, Pages 579-592: A New CPX Drum Test to Obtain Sound
Pressure Levels of Tyre Noise for Type Approval
Authors: David Clar-Garcia, Hector Campello-Vicente, Nuria Campillo-Davo, Miguel Sanchez-Lozano, Emilio Velasco-Sanchez
First page: 579
Abstract: The primary cause of noise from vehicular traffic while travelling at speeds over 30 km/h is tyre/road interaction. To reduce this noise source, tyre/road sound emissions research has been carried out using different approaches. Most of this research has been centred around track tests, leading to the development of various track and road-based methods for evaluating tyre/road noise emissions. The CPX (Close-Proximity), along with the CPB (Controlled Pass-By), the CB (Coast-By) and the SPB (Statistical Pass-By), methods are the most common ones. Nevertheless, since Reg. (EC) 1222/2009 came into force, only the CB method, defined in Reg. (EC) 117/2007, can be used to obtain tyre/road noise emission type approval values in Europe. However, current track test methods have important limitations, such as the variability of the results depending on the test track or the test vehicle, the repeatability, the influence of environmental variables or, the main aspect, the limitation of the registered magnitude in these tests, which is the sound pressure level. The Alternative Drum test method (A-DR) was developed in 2015 in order to avoid these disadvantages. However, it involves a complex and time-consuming microphone array for each test. With the purpose of improving the A-DR test method, a new methodology based on drum tests, the ISO 11819-2 and the ISO 3744 standards, was developed. This paper describes the new Alternative CPX Drum test method (A-CPX-DR) and validates it by testing several tyres according to the CB, the A-DR and the A-CPX-DR test methods and comparing their results. This research has demonstrated that all three methods have equivalent sound spectra and obtain close equivalent sound pressure levels for type approval of tyres in the EU, while drum tests have shown greater accuracy. For both reasons, the new A-CPX-DR methodology could be used for tyre/road noise emission type approval in a more precise and cheaper way.
Citation: Acoustics
PubDate: 2024-06-28
DOI: 10.3390/acoustics6030031
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 593-609: Ultrasonic Study of Longitudinal
Critically Refracted and Bulk Waves of the Heat-Affected Zone of a
Low-Carbon Steel Welded Joint under Fatigue
Authors: Alexander Gonchar, Alexander Solovyov, Vyacheslav Klyushnikov
First page: 593
Abstract: Currently, ultrasonic methods for assessing the fatigue lifetime of various structural materials are being actively developed. Many steel constructions are made by welding. The weld heat-affected zone is the weak point of the construction, as it is most susceptible to destruction. Therefore, it is actually important to search for acoustic parameters that uniquely characterize the structural damage accumulation in the heat-affected zone of a welded joint in order to predict failure. In this work, the specimens were made from the base metal and the welded joint’s heat-affected zone. The specimens were subjected to uniaxial tension–compression under a symmetrical cycle in the region of low-cycle fatigue with control of the strain amplitude. The propagation bulk velocities of longitudinal, shear waves and subsurface longitudinal critically refracted (LCR) waves during cyclic loading were studied. The acoustic birefringence of shear waves was calculated, and a similar parameter was proposed for longitudinal and LCR waves. The dependence of the elastic modulus ratio on the cycle ratio was obtained. It was shown that the acoustic parameters change most intensively in the heat-affected zone. According to the data of the C33/C55 ratio changes measured through the ultrasonic method, a formula for calculating the remaining fatigue life in the heat-affected zone was proposed.
Citation: Acoustics
PubDate: 2024-06-29
DOI: 10.3390/acoustics6030032
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 610-619: On the Applicability of
Kramers–Kronig Dispersion Relations to Guided and Surface Waves
Authors: Victor V. Krylov
First page: 610
Abstract: In unbounded media, the acoustic attenuation as function of frequency is related to the frequency-dependent sound velocity (dispersion) via Kramers–Kronig dispersion relations. These relations are fundamentally important for better understanding of the nature of attenuation and dispersion and as a tool in physical acoustics measurements, where they can be used for control purposes. However, physical acoustic measurements are frequently carried out not in unbounded media but in acoustic waveguides, e.g., inside liquid-filled pipes. Surface acoustic waves are also often used for physical acoustics measurements. In the present work, the applicability of Kramers–Kronig relations to guided and surface waves is investigated using the approach based on the theory of functions of complex variables. It is demonstrated that Kramers–Kronig relations have limited applicability to guided and surface waves. In particular, they are not applicable to waves propagating in waveguides characterised by the possibility of wave energy leakage from the waveguides into the surrounding medium. For waveguides without leakages, e.g., those formed by rigid walls, Kramers–Kronig relations remain valid for both ideal and viscous liquids. Examples of numerical calculations of wave dispersion and attenuation using Kramers–Kronig relations, where applicable, are presented for unbounded media and for waveguides formed by two rigid walls.
Citation: Acoustics
PubDate: 2024-06-29
DOI: 10.3390/acoustics6030033
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 620-637: Measurement and Simulation of the
Propagation of Impulsive Acoustic Emission Sources in Pipes
Authors: Chika Judith Abolle-Okoyeagu, Samuel Fatukasi, Bob Reuben
First page: 620
Abstract: Abstract: Acoustic Emission (AE) testing is a non-destructive evaluation technique that has gained significant attention in pipeline monitoring. Pencil-lead breaks (PLBs) are commonly used in reproducing and characterising sensors used in AE applications and have emerged as a valuable tool for calibration processes. This technique involves breaking a pencil lead by pressing it on the surface of the test structure and applying a bending moment at a given angle on a surface. The applied force produces a local deformation on the test surface, which is released when the lead breaks. The fracture in these PLBs is assumed to be a step unload; however, this is not the case. In this work, a series of PLB source experiments complemented with parallel numerical simulations were carried out to investigate the actual unload rate by correlating the relationship between AE speed, frequency, and power from PLBs. This was achieved by varying the simulation unload rates recorded over a duration of 2 s on a steel pipe and comparing to the experiment. Analysis of the investigated results from the experimental and numerical models suggests that although the AE line structure of a PLB can be reproduced by simulation for short times only (1 µs), the actual unload rate for PLBs is in the region of 10–8 s. It is concluded that FEA has the potential to help in the recovery of the temporal structure from real AE structures. The establishment of this model will provide a theoretical basis for future studies on the monitoring of non-impulsive AE sources such as impact on pipelines using finite element analysis.
Citation: Acoustics
PubDate: 2024-06-30
DOI: 10.3390/acoustics6030034
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 638-650: Silent Neonatal Incubators, Prototype
Nica+
Authors: Ricardo Hernández-Molina, Virginia Puyana-Romero, Juan Luis Beira-Jiménez, Arturo Morgado-Estévez, Rafael Bienvenido-Bárcena, Francisco Fernández-Zacarías
First page: 638
Abstract: Objectives: The purpose of this study was to evaluate and compare the noise levels in current incubator models and a prototype designed to improve acoustic comfort in neonatal incubators. Methods: Tests were carried out on three different models of incubators and a prototype called Neonatal Incubator Acoustic Comfort Class (NICA). The tests measured both internal and external sound pressure levels under laboratory conditions. The noise index has been taken as the A-weighted equivalent continuous sound pressure level (LAeq,T) for a time interval of 1 min. Results: The results obtained show variations between the different models of incubators, although, overall, they are high values (around 56/60 dBA). The results prove that premature newborns under normal conditions of using these incubators are exposed to noise levels above international recommendations. The new incubator design minimizes noise generation and generates noise levels lower than international recommendations. Conclusions: The results obtained from the prototype (NICA+) show the effectiveness of the proposed design in improving acoustic comfort in neonatal incubators. The data show that the noise levels generated by the prototype under normal operating conditions are significantly lower than international recommendations.
Citation: Acoustics
PubDate: 2024-07-15
DOI: 10.3390/acoustics6030035
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 651-680: A Study on Adaptive
Implicit–Explicit and Explicit–Explicit Time Integration
Procedures for Wave Propagation Analyses
Authors: Delfim Soares, Isabelle de Souza Sales, Lucas Ruffo Pinto, Webe João Mansur
First page: 651
Abstract: This study delves into the effectiveness of two time integration techniques, namely the adaptive implicit–explicit (imp–exp) and explicit–explicit (exp–exp) methods, which stand as efficient formulations for tackling intricate systems characterized by multiple time scales. The imp–exp technique combines implicit and explicit procedures by employing implicit formulations for faster components and explicit calculations for slower ones, achieving high accuracy and computational efficiency. Conversely, the exp–exp method, a variation of explicit methods with sub-cycling, excels in handling locally stiff systems by employing smaller sub-steps to resolve rapid changes while maintaining stability. For both these approaches, numerical damping may be activated by adaptive time integration parameters, allowing numerical dissipation to be locally applied, if necessary, as a function of the considered discrete model and its computed responses, enabling a highly effective numerical dissipative algorithm. Furthermore, both these techniques stand as very simple and straightforward formulations as they rely solely on single-step displacement–velocity relations, describing truly self-starting procedures, and they stand as entirely automated methodologies, requiring no effort nor expertise from the user. This work provides comparative studies of the adaptive imp–exp and exp–exp approaches to assess their accuracy and efficiency across a wide range of scenarios, with emphasis on geophysical applications characterized by multiscale problems, aiming to establish under which circumstances one approach should be preferred over the other.
Citation: Acoustics
PubDate: 2024-07-23
DOI: 10.3390/acoustics6030036
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 681-697: Application of Machine Learning
Techniques for Predicting Students’ Acoustic Evaluation in a
University Library
Authors: Dadi Zhang, Kwok-Wai Mui, Massimiliano Masullo, Ling-Tim Wong
First page: 681
Abstract: Understanding students’ acoustic evaluation in learning environments is crucial for identifying acoustic issues, improving acoustic conditions, and enhancing academic performance. However, predictive models are not specifically tailored to predict students’ acoustic evaluations, particularly in educational settings. To bridge this gap, the present study conducted a field investigation in a university library, including a measurement and questionnaire survey. Using the collected personal information, room-related parameters, and sound pressure levels as input, six machine learning models (Support Vector Machine–Radial Basis Function (SVM (RBF)), Support Vector Machine–Sigmoid (SVM (Sigmoid)), Gradient Boosting Machine (GBM), Logistic Regression (LR), Random Forest (RF), and Naïve Bayes (NB)) were trained to predict students’ acoustic acceptance/satisfaction. The performance of these models was evaluated using five metrics, allowing for a comparative analysis. The results revealed that the models better predicted acoustic acceptance than acoustic satisfaction. Notably, the RF and GBM models exhibited the highest performance, with accuracies of 0.87 and 0.84, respectively, in predicting acoustic acceptance. Conversely, the SVM models performed poorly and were not recommended for acoustic quality prediction. The findings of this study demonstrated the feasibility of employing machine learning models to predict occupants’ acoustic evaluations, thereby providing valuable insights for future acoustic assessments.
Citation: Acoustics
PubDate: 2024-07-25
DOI: 10.3390/acoustics6030037
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 698-712: Acoustic Analysis of a Hybrid Propulsion
System for Drone Applications
Authors: Mădălin Dombrovschi, Marius Deaconu, Laurentiu Cristea, Tiberius Florian Frigioescu, Grigore Cican, Gabriel-Petre Badea, Andrei-George Totu
First page: 698
Abstract: This paper aims to conduct an acoustic analysis through noise measurements of a hybrid propulsion system intended for implementation on a drone, from which the main noise sources can be identified for further research on noise reduction techniques. Additionally, the noise was characterized by performing spectral analysis and identifying the tonal components that contribute to the overall noise. The propelling force system consists of a micro-turboshaft coupled with a gearbox connected to an electric generator. The propulsion system consists of a micro-turboshaft coupled with a gearbox connected to an electric generator. The electric current produced by the generator powers an electric ducted fan (EDF). The engineturbo-engine was tested in free-field conditions for noise generation at different speeds, and for this, an array of microphones was installed, positioned polarly around the system and near the intake and exhaust. Consequently, based on the test results, the acoustic directivity was plotted, revealing that the highest noise levels are at the front and rear of the engine. The noise level at a distance of 1.5 m from the turboengine exceeds 90 dBA at all tested speeds. Spectral analyses of both the far-field acoustic signals (measured with a polar microphone array) and the near-field signals (microphones positioned near the intake and exhaust) revealed that the primary contributors to the overall noise are the micromotor’s compressor, specifically the gas dynamic phenomena in the fan (BPF and 2× BPF). Thus, it was determined that at the intake level, the main noise contribution comes from the high-frequency components of the compressor, while at the exhaust level, the noise mainly originates from the combustion chamber, characterized by low-frequency components (up to 2 kHz). The findings from this study have practical applications in the design and development of quieter drone propulsion systems. By identifying and targeting the primary noise sources, engineers can implement effective noise reduction strategies, leading to drones that are less disruptive in urban environments and other noise-sensitive areas. This can enhance the acceptance and deployment of drone technology in various sectors, including logistics, surveillance, and environmental monitoring.
Citation: Acoustics
PubDate: 2024-07-25
DOI: 10.3390/acoustics6030038
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 713-729: A Frequency-Independent Phase Shifter
Authors: Máté Csanád, Amira K. F. Val Baker, Paul Oomen
First page: 713
Abstract: In this paper, we utilise optimization methods to determine a frequency-independent phase shift such that two phase-shifted versions of a signal can be summed and the resulting amplitude spectrum is unchanged. A phase difference between two signals is thus defined, which remains constant for all frequencies within a given range. For the intended purpose of this study, we set the frequency range to the audible human hearing range of 16 Hz–20 kHz. We found that a new 3-stage filter method provides a variable phase shifter (i.e., ϕ = 0–360°) without the need for additional amplifiers. In addition, we present a new method that reduces the number of filters necessary, improving both the accuracy and efficiency of current techniques.
Citation: Acoustics
PubDate: 2024-07-31
DOI: 10.3390/acoustics6030039
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 730-753: Feasibility Analysis for Active Noise
Cancellation Using the Electrical Power Steering Motor
Authors: Dominik Schubert, Simon Hecker, Stefan Sentpali, Martin Buss
First page: 730
Abstract: This paper describes the use of an electric drive as an acoustic actuator for active noise cancellation (ANC). In the presented application, the idea is to improve the noise, vibration, harshness (NVH) characteristics of passenger cars without using additional active or passive damper systems. Many of the already existing electric drives in cars are equipped with the required hardware components to generate noise and vibration, which can be used as compensation signals in an ANC application. To demonstrate the applicability of the idea, the electrical power steering (EPS) motor is stimulated with a control signal, generated by an adaptive feedforward controller, to reduce harmonic disturbances at the driver’s ears. As it turns out, the EPS system generates higher harmonics of the harmonic compensation signal due to nonlinearities in the acoustic transfer path using a harmonic excitation signal. The higher harmonics impair an improvement in the subjective hearing experience, although the airborne noise level of the harmonic disturbance signal can be clearly reduced at the driver’s ears. Therefore, two methods are presented to reduce the amplitude of the higher harmonics. The first method is to limit the filter weights of the algorithm to reduce the amplitude of the harmonic compensation signal. The filter amplitude limitation also leads to a lower amplitude of the higher harmonics, generated by the permanent magnet synchronous machine (PMSM). The second method uses a parallel structure of adaptive filters to actively reduce the amplitude of the higher harmonics. Finally, the effectiveness of the proposed ANC system is demonstrated in two real driving situations, where in one case a synthetic noise/vibration induced by a shaker on the front axle carrier is considered to be the disturbance, and in the other case, the disturbance is a harmonic vibration generated by the combustion engine. In both cases, the subjective hearing experience of the driver could be clearly improved using the EPS motor as ANC actuator.
Citation: Acoustics
PubDate: 2024-07-31
DOI: 10.3390/acoustics6030040
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 754-771: The Historical Building and Room
Acoustics of the Stockholm Public Library (1925–28, 1931–32)
Authors: Patrick H. Fleming
First page: 754
Abstract: The Stockholm Public Library was realized in two distinct phases of construction in the 1920s and early 1930s, and remains a well-known work in twentieth-century architecture, with a heritage status today. While previous studies have focused on the library’s architectural design, particularly its lighting, acoustics were also an important aspect of the building’s design and construction. This study marks the first detailed investigation of the library’s architectural acoustics, with a suite of standard measurements performed to assess and characterize the library’s historical room and building acoustics. Reverberation time measurements in the library’s reading rooms yielded results of about 1.5–2 s for frequencies associated with speech. A significantly longer reverberation time of 5–6 s was measured in the library’s central rotunda, confirming a prominent acoustic issue in the library, where appropriate heritage discussions are needed in the future as the library undergoes a major renovation in the coming years. A comparison of the measured airborne and impact sound insulation of the 1920s and 1930s reading room ceilings also yielded interesting results. While the materials in library’s two construction periods are notably different, the airborne sound insulation performance of the 1920s and 1930s floors or ceilings was comparable and in line with contemporary standards. Impact sound insulation results from the 1920s and 1930s floors, however, differed significantly, with the latter displaying a relatively poor performance. Flanking transmission effects related to historical construction details and deviations from archival plans were investigated and discussed. This work emphasizes the practical and academic importance of conducting on-site measurements, and the close mutual development of modern architecture, construction, and architectural acoustics.
Citation: Acoustics
PubDate: 2024-08-19
DOI: 10.3390/acoustics6030041
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 772-781: Text-Independent Phone-to-Audio
Alignment Leveraging SSL (TIPAA-SSL) Pre-Trained Model Latent
Representation and Knowledge Transfer
Authors: Noé Tits, Prernna Bhatnagar, Thierry Dutoit
First page: 772
Abstract: In this paper, we present a novel approach for text-independent phone-to-audio alignment based on phoneme recognition, representation learning and knowledge transfer. Our method leverages a self-supervised model (Wav2Vec2) fine-tuned for phoneme recognition using a Connectionist Temporal Classification (CTC) loss, a dimension reduction model and a frame-level phoneme classifier trained using forced-alignment labels (using Montreal Forced Aligner) to produce multi-lingual phonetic representations, thus requiring minimal additional training. We evaluate our model using synthetic native data from the TIMIT dataset and the SCRIBE dataset for American and British English, respectively. Our proposed model outperforms the state-of-the-art (charsiu) in statistical metrics and has applications in language learning and speech processing systems. We leave experiments on other languages for future work but the design of the system makes it easily adaptable to other languages.
Citation: Acoustics
PubDate: 2024-08-29
DOI: 10.3390/acoustics6030042
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 782-791: A Power Law Reconstruction of Ultrasound
Backscatter Images
Authors: Kevin J. Parker
First page: 782
Abstract: Ultrasound B-scan images are traditionally formed from the envelope of the received radiofrequency echoes, but the image texture is dominated by granular speckle patterns. Longstanding efforts at speckle reduction and deconvolution have been developed to lessen the detrimental aspects of speckle. However, we now propose an alternative approach to estimation (and image rendering) of the underlying fine grain scattering density of tissues based on power law constraints. The key steps are a whitening of the spectrum of the received signal while conforming to the original envelope shape and statistics, followed by a power law filtering in accordance with the known scattering behavior of tissues. This multiple step approach results in a high-spatial-resolution map of scattering density that is constrained by the most important properties of scattering from tissues. Examples from in vivo liver scans are shown to illustrate the change in image properties from this framework.
Citation: Acoustics
PubDate: 2024-08-31
DOI: 10.3390/acoustics6030043
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 792-804: A Decoupled Modal Reduction Method for
the Steady-State Vibration Analysis of Vibro-Acoustic Systems with
Non-Classical Damping
Authors: Ruxin Gao, Shanshan Fan
First page: 792
Abstract: This paper presents a decoupled modal reduction method for the steady-state vibration analysis of vibro-acoustic systems characterized by non-classical damping. The proposed approach initially reduces the order of the coupled governing equations of the vibro-acoustic system through the utilization of non-coupled modes, subsequently employing the complex mode superposition technique to address non-classical damping effects. By leveraging non-coupled modes, this method circumvents the need to solve for coupled modes as required in traditional modal reduction techniques, thereby diminishing both computational complexity and cost. Furthermore, the complex mode superposition method facilitates the decoupling of coupled governing equations with non-classical damping, enhancing computational efficiency. Numerical examples validate both the accuracy and effectiveness of this methodology. Given that modal decomposition is independent of frequency, an analysis of computational efficiency across various stages further substantiates that this method offers significant advantages in terms of efficiency for computational challenges encountered over a broad frequency range.
Citation: Acoustics
PubDate: 2024-09-23
DOI: 10.3390/acoustics6030044
Issue No: Vol. 6, No. 3 (2024)
- Acoustics, Vol. 6, Pages 298-330: Research Progress on Thin-Walled Sound
Insulation Metamaterial Structures
Authors: Yumei Zhang, Jie Zhang, Ye Li, Dan Yao, Yue Zhao, Yi Ai, Weijun Pan, Jiang Li
First page: 298
Abstract: Acoustic metamaterials (AMs) composed of periodic artificial structures have extraordinary sound wave manipulation capabilities compared with traditional acoustic materials, and they have attracted widespread research attention. The sound insulation performance of thin-walled structures commonly used in engineering applications with restricted space, for example, vehicles’ body structures, and the latest studies on the sound insulation of thin-walled metamaterial structures, are comprehensively discussed in this paper. First, the definition and math law of sound insulation are introduced, alongside the primary methods of sound insulation testing of specimens. Secondly, the main sound insulation acoustic metamaterial structures are summarized and classified, including membrane-type, plate-type, and smart-material-type sound insulation metamaterials, boundaries, and temperature effects, as well as the sound insulation research on composite structures combined with metamaterial structures. Finally, the research status, challenges, and trends of sound insulation metamaterial structures are summarized. It was found that combining the advantages of metamaterial and various composite panel structures with optimization methods considering lightweight and proper wide frequency band single evaluator has the potential to improve the sound insulation performance of composite metamaterials in the full frequency range. Relative review results provide a comprehensive reference for the sound insulation metamaterial design and application.
Citation: Acoustics
PubDate: 2024-03-26
DOI: 10.3390/acoustics6020016
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 331-345: Curvature Correction for Crack Depth
Measurement Using Ultrasonic Pulse Velocity
Authors: Dong Liu, Mengli Wu, Dimitri Donskoy
First page: 331
Abstract: This study investigates the application of Ultrasonic Pulse Velocity (UPV) for crack depth estimation in cylindrical structures, focusing on two approaches: reference measurement and dual measurement. It addresses the challenge of applying UPV to curved surfaces, a scenario less studied than that of flat surfaces. The paper details the modification of UPV methodologies to account for curvature, presenting analytic solutions and numerical validations for both approaches. The findings reveal that curvature-adjusted equations yield accurate crack depth estimations, enhancing the reliability of UPV in diverse structural contexts. The study contributes to safer and more effective structural health monitoring, particularly in cylindrical infrastructures like columns and foundations.
Citation: Acoustics
PubDate: 2024-03-27
DOI: 10.3390/acoustics6020017
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 346-361: A Two-Dimensional Liquid Sloshing
Analysis in a Partially Filled Complicated-Shape Tank by the
Schwarz–Christoffel Transformation
Authors: Jing Lü, Xiaolong Zhu, Yang Yu
First page: 346
Abstract: The nonlinear sloshing of an incompressible fluid with irrotational flow in a complicated-shape tank due to horizontal excitation is studied with a semi-analytical method proposed in this study. In this method, the velocity potential function of a liquid in a complicated-shape tank is estimated by using an approximate analytical transformation function from a complicated-shape region to a rectangular region. This function is obtained through Schwarz–Christoffel mapping and polynomial fitting. Nonlinear dynamic equations for the fluid–structure coupled system are developed based on the Hamilton–Ostrogradskiy principle. Nonlinear kinematic equations for the fluid–structure coupled system are derived based on the relationship between the liquid velocity and the free-surface equation. The Galerkin method is used to convert partial differential equations into ordinary differential equations. When tank movement is given, nonlinear models for the coupled system can be reduced to simple ones for liquid sloshing. Natural frequencies for the coupled system and liquid sloshing are analyzed, and the semi-analytical results agree with the numerical ones calculated with the software DampSlosh. Hydrodynamic forces and moments are also analyzed, and the semi-analytical results agree well with the numerical ones calculated with the Flow3D v10.1.1.
Citation: Acoustics
PubDate: 2024-04-19
DOI: 10.3390/acoustics6020018
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 362-373: Tunnel Effect for Ultrasonic Waves in
Tapered Waveguides
Authors: Massimo Germano
First page: 362
Abstract: Traversal time in the tunneling effect for ultrasonic waves in tapered waveguides is derived considering its analogy with quantum and electromagnetic wave tunneling. If, as traversal time, the so-called phase time is considered, the ultrasonic wave packet shows the equivalent in acoustics of superluminality, i.e., the derived velocity, crosses the limit of bulk transverse ultrasonic waves in the medium of the waveguide that is the equivalent of c in the quantum and electromagnetic cases. The graphs clearly illustrating this so-called Hartman effect are obtained confirming the experimental results in the three different fields.
Citation: Acoustics
PubDate: 2024-04-24
DOI: 10.3390/acoustics6020019
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 374-385: Modelling of Propagation Characteristics
of Acoustic Pulse from Partial Discharge in Polymeric Insulating Materials
Authors: Abdul Samad, Wah Hoon Siew, Martin J. Given, Igor V. Timoshkin, John Liggat
First page: 374
Abstract: The partial discharge (PD) event in high-voltage insulation releases energy, exerts mechanical pressure, and generates elastic waves. Detecting and locating these PD events through short-duration acoustic pulses is well established, particularly in gas-insulated systems and oil-insulated transformers. However, its full potential remains untapped in solid insulation systems, where the propagation capability of the acoustic pulse and the acoustic reflections pose fundamental challenges to the acoustic emission (AE) detection technique. This study investigates the influence of reflections and multiple paths on the propagating acoustic pulse in polymeric insulating materials using a finite element method (FEM) in COMSOL. It was observed that the reflections from the boundary influence the propagating pulse’s shape, peak magnitude, and arrival time. An analytical MATLAB model further quantifies the impact of multiple propagation paths on the shape, magnitude, and arrival time of the pulse travelling in a cylinder. Additionally, a Perfect Matched Layer (PML) was implemented in the COMSOL model to eliminate the reflections from the boundary, and it revealed that the acoustic pulse magnitude decreases with distance following the inverse square law. In essence, the models aid in measuring how reflections contribute to the observed signals, facilitating the precise identification of the source of the PD event in the tested system.
Citation: Acoustics
PubDate: 2024-04-26
DOI: 10.3390/acoustics6020020
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 386-407: Effect of Emotionalizing Sounds on the
Estimation and Evaluation of Displayed Safety Distances
Authors: Manuel Petersen, Deniz Yüksel, Albert Albers
First page: 386
Abstract: Musicological and traffic psychology research shows that emotions can be changed by certain tone combinations or sound characteristics and that emotions, in turn, influence our driving behavior. Nevertheless, there are no studies on how a dynamic active sound design could influence driving behavior via changing the emotional state of drivers in certain driving situations. Based on a previous study, emotionalizing sounds, characterized by their capacity to evoke specific emotional responses in individuals, were created and used to investigate their effect on the perception of safety distances in an online study. To test this, participants made statements on the safety distance shown in videos of cars following scenarios combined with emotionalizing sounds. The results show a significant difference in the estimated safety distance for videos combined with sounds invoking positive emotions like light-heartedness vs. sounds invoking negative emotions like feeling threatened. The odds of the safety distance being evaluated as too small compared with appropriate were two to three times higher for some threatening sounds vs. the positive sounds. The results further suggest that threatening sounds influenced participants’ wishes to increase the depicted safety distances. The results show that emotionalizing sounds had effects on the participants, though not all were statistically significant.
Citation: Acoustics
PubDate: 2024-04-30
DOI: 10.3390/acoustics6020021
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 408-412: Acoustics, Soundscapes and Sounds as
Intangible Heritage
Authors: Lidia Alvarez-Morales, Margarita Díaz-Andreu
First page: 408
Abstract: Since UNESCO unveiled its declaration for an integrated approach to safeguarding tangible and intangible cultural heritage in 2003 [...]
Citation: Acoustics
PubDate: 2024-05-02
DOI: 10.3390/acoustics6020022
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 413-438: Angular Integral Autocorrelation for
Speed Estimation in Shear-Wave Elastography
Authors: Hamidreza Asemani, Irteza Enan Kabir, Juvenal Ormachea, Marvin M. Doyley, Jannick P. Rolland, Kevin J. Parker
First page: 413
Abstract: The utilization of a reverberant shear-wave field in shear-wave elastography has emerged as a promising technique for achieving robust shear-wave speed (SWS) estimation. However, many types of estimators cannot accurately measure SWS within such a complicated 3D wave field. This study introduces an advanced autocorrelation estimator based on angular integration known as the angular integral autocorrelation (AIA) approach to address this issue. The AIA approach incorporates all the autocorrelation data from various angles during measurements, resulting in enhanced robustness to both noise and imperfect distributions in SWS estimation. The effectiveness of the AIA estimator for SWS estimation is first validated using a k-Wave simulation of a stiff branching tube in a uniform background. Furthermore, the AIA estimator is applied to ultrasound elastography experiments, magnetic resonance imaging (MRI) experiments, and optical coherence tomography (OCT) studies across a range of different excitation frequencies on tissues and phantoms, including in vivo scans. The results verify the capacity of the AIA approach to enhance the accuracy of SWS estimation and the signal-to-noise ratio (SNR), even within an imperfect reverberant shear-wave field. Compared to simple autocorrelation approaches, the AIA approach can also successfully visualize and define lesions while significantly improving the estimated SWS and SNR in homogeneous background materials and providing improved elastic contrast between structures within the scans. These findings demonstrate the robustness and effectiveness of the AIA approach across a wide range of applications, including ultrasound elastography, magnetic resonance elastography (MRE), and optical coherence elastography (OCE), for accurately identifying the elastic properties of biological tissues in diverse excitation scenarios.
Citation: Acoustics
PubDate: 2024-05-09
DOI: 10.3390/acoustics6020023
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 439-469: Enhancing Speaker Recognition Models
with Noise-Resilient Feature Optimization Strategies
Authors: Neha Chauhan, Tsuyoshi Isshiki, Dongju Li
First page: 439
Abstract: This paper delves into an in-depth exploration of speaker recognition methodologies, with a primary focus on three pivotal approaches: feature-level fusion, dimension reduction employing principal component analysis (PCA) and independent component analysis (ICA), and feature optimization through a genetic algorithm (GA) and the marine predator algorithm (MPA). This study conducts comprehensive experiments across diverse speech datasets characterized by varying noise levels and speaker counts. Impressively, the research yields exceptional results across different datasets and classifiers. For instance, on the TIMIT babble noise dataset (120 speakers), feature fusion achieves a remarkable speaker identification accuracy of 92.7%, while various feature optimization techniques combined with K nearest neighbor (KNN) and linear discriminant (LD) classifiers result in a speaker verification equal error rate (SV EER) of 0.7%. Notably, this study achieves a speaker identification accuracy of 93.5% and SV EER of 0.13% on the TIMIT babble noise dataset (630 speakers) using a KNN classifier with feature optimization. On the TIMIT white noise dataset (120 and 630 speakers), speaker identification accuracies of 93.3% and 83.5%, along with SV EER values of 0.58% and 0.13%, respectively, were attained utilizing PCA dimension reduction and feature optimization techniques (PCA-MPA) with KNN classifiers. Furthermore, on the voxceleb1 dataset, PCA-MPA feature optimization with KNN classifiers achieves a speaker identification accuracy of 95.2% and an SV EER of 1.8%. These findings underscore the significant enhancement in computational speed and speaker recognition performance facilitated by feature optimization strategies.
Citation: Acoustics
PubDate: 2024-05-14
DOI: 10.3390/acoustics6020024
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 470-488: Training a Filter-Based Model of the
Cochlea in the Context of Pre-Trained Acoustic Models
Authors: Louise Coppieters de Gibson, Philip N. Garner
First page: 470
Abstract: Auditory research aims in general to lead to understanding of physiological processes. By contrast, the state of the art in automatic speech processing (notably recognition) is dominated by large pre-trained models that are meant to be used as black-boxes. In this work, we integrate a physiologically plausible (albeit simple filter-based) model of the cochlea into a much larger pre-trained acoustic model for speech recognition. We show that the hybrid system can be trained and evaluated with various combinations of fine-tuning and self-supervision. The results broadly show that the system automatically yields structures that are known to work well. Moreover, these structures lack artifacts that were apparent in (our) previous work using less sophisticated neural models. We conclude that the hybrid structure is an appropriate way to proceed in auditory research, more generally allowing the work to take advantage of larger models and databases from which it would not otherwise benefit.
Citation: Acoustics
PubDate: 2024-05-17
DOI: 10.3390/acoustics6020025
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 489-508: Atmospheric Sound Propagation over Rough
Sea: Numerical Evaluation of Equivalent Acoustic Impedance of Varying Sea
States
Authors: Andrea Vecchiotti, Teresa J. Ryan, Joseph F. Vignola, Diego Turo
First page: 489
Abstract: This work presents a numerical study on atmospheric sound propagation over rough water surfaces with the aim of improving predictions of sound propagation over long distances. A method for generating pseudorandom sea profiles consistent with sea wave spectra is presented. The proposed method is suited for capturing the logarithmic nature of the energy distribution of the waves. Sea profiles representing fully developed seas for sea states 2, 3, 4, and 5 are generated from the Elfouhaily et al. (ECKV) sea wave spectra. Excess attenuation caused by refraction and surface roughness is predicted with a parabolic equation (PE) solver. A novel method for estimating equivalent effective impedance based on PE predictions at different sea states is presented. Parametric expressions using acoustic frequency and significant wave height are developed for effective surface impedances. In this work, sea surface roughness is on a scale comparable with the acoustic wavelength. Under this condition, the acoustic scattering is primarily incoherent. This work shows the limitations of using an equivalent surface impedance in such incoherent scattering cases.
Citation: Acoustics
PubDate: 2024-05-23
DOI: 10.3390/acoustics6020026
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 509-522: Acoustic Properties of Surfaces Covered
by Multipole Resonators
Authors: Nikolay Kanev
First page: 509
Abstract: Different types of resonators are used to create acoustic metamaterials and metasurfaces. Recent studies focused on the use of multiple resonators of the dipole, quadrupole, octupole, and even hexadecapole types. This paper considers the theory of an acoustic metasurface, which is a flat surface with a periodic arrangement of multipole resonators. The sound field reflected by the metasurface is determined. If the distance between the resonators is less than half the wavelength of the incident plane wave, the far field can be described by a reflection coefficient that depends on the angle of incidence. This allows us to characterize the acoustic properties of the metasurface by a homogenized boundary condition, which is a high-order tangential impedance boundary condition. The tangential impedance depending on the multipole order of the resonators is introduced. In addition, we analyze the sound absorption properties of these metasurfaces, which are a critical factor in determining their performance. The paper presents a theoretical model for the subwavelength case that accounts for the multipole orders of resonators and their impact on sound absorption. The maximum absorption coefficient for a diffuse sound field, as well as the optimal value for the homogenized impedance, are calculated for arbitrary multipole orders. The examples of the multipole resonators, which can be made from a set of Helmholtz resonators or membrane resonators, are discussed as well.
Citation: Acoustics
PubDate: 2024-05-25
DOI: 10.3390/acoustics6020027
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 523-540: Prediction of Time Domain Vibro-Acoustic
Response of Conical Shells using Jacobi–Ritz Boundary Element Method
Authors: Cong Gao, Jiajun Zheng, Fuzhen Pang, Jiawei Xu, Haichao Li, Jibing Yan
First page: 523
Abstract: Considering the lack of studies on the transient vibro-acoustic properties of conical shell structures, a Jacobi–Ritz boundary element method for forced vibro-acoustic behaviors of structure is proposed based on the Newmark-β integral method and the Kirchhoff time domain boundary integral equation. Based on the idea of the differential element method and the first-order shear deformation theory (FSDT), the vibro-acoustic model of conical shells is established. The axial and circumferential displacement tolerance functions are expressed using Jacobi polynomials and the Fourier series. The time domain response of the forced vibration of conical shells is calculated based on the Rayleigh–Ritz method and Newmark-β integral method. On this basis, the time domain response of radiated noise is solved based on the Kirchhoff integral equation, and the acoustic radiation characteristics of conical shells from forced vibration are analyzed. Compared with the coupled FEM/BEM method, the numerical results demonstrate the high accuracy and great reliability of this method. Furthermore, the semi-vertex angle, load characteristics, and boundary conditions related to the vibro-acoustic response of conical shells are examined.
Citation: Acoustics
PubDate: 2024-05-31
DOI: 10.3390/acoustics6020028
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 541-567: The Effect of an Emotionalizing Sound
Design on the Driver’s Choice of Headway in a Driving Simulator
Authors: Manuel Petersen, Barbara Deml, Albert Albers
First page: 541
Abstract: This study investigates the impact of emotionalizing sound design on driving behaviour, focusing on the effect of an acoustic stimulus that varies from positive to negative/threatening based on the vehicle’s time headway (THW). Our primary goal was to explore how this sound influences driving durations within specific THW ranges and the mean THW itself. The experiment utilized a control group and a within-participant setting across simulated driving scenarios. The statistical analysis showed mixed results. While participants in the control group setup did not demonstrate significant reductions in the durations of driving in lower THW ranges, a modest but significant increase in mean THW was observed when the emotionalizing sound was active. However, within-participant comparisons showed both a significant decrease in the duration of driving at lower THWs and an increase in mean THW when the negative stimulus was active, suggesting the stimulus’ effectiveness in promoting safer driving habits. These findings highlight the potential of emotionalizing sound design to influence driver behaviour towards maintaining safer distances, although the impact appears to diminish at higher THW ranges. Future research should further investigate the characteristics of sounds that effectively modify driving behaviour, aiming for broader applications in traffic safety.
Citation: Acoustics
PubDate: 2024-06-10
DOI: 10.3390/acoustics6020029
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 568-578: Acoustic Analyses of L1 and L2 Vowel
Interactions in Mandarin–Cantonese Late Bilinguals
Authors: Yike Yang
First page: 568
Abstract: While the focus of bilingual research is frequently on simultaneous or early bilingualism, the interactions between late bilinguals’ first language (L1) and second language (L2) have rarely been studied previously. To fill this research gap, the aim of the current study was to investigate the production of vowels in the L1 Mandarin and L2 Cantonese of Mandarin–Cantonese late bilinguals in Hong Kong. A production experiment was conducted with 22 Mandarin–Cantonese bilinguals, as well as with 20 native Mandarin speakers and 21 native Cantonese speakers. Acoustic analyses, including formants of and Euclidean distances between the vowels, were performed. Both vowel category assimilation and dissimilation were noted in the Mandarin–Cantonese bilinguals’ L1 and L2 vowel systems, suggesting interactions between the bilinguals’ L1 and L2 vowel categories. In general, the findings are in line with the hypotheses of the Speech Learning Model and its revised version, which state that L1–L2 phonetic interactions are inevitable, as there is a common phonetic space for storing the L1 and L2 phonetic categories, and that learners always have the ability to adapt their phonetic space. Future studies should refine the data elicitation method, increase the sample size and include more language pairs to better understand L1 and L2 phonetic interactions.
Citation: Acoustics
PubDate: 2024-06-17
DOI: 10.3390/acoustics6020030
Issue No: Vol. 6, No. 2 (2024)
- Acoustics, Vol. 6, Pages 35-64: Music Listening as Kangaroo Mother Care:
From Skin-to-Skin Contact to Being Touched by the Music
Authors: Mark Reybrouck
First page: 35
Abstract: The metaphor of being touched by music is widespread and almost universal. The tactile experience, moreover, has received growing interest in recent years. There is, however, a need to go beyond a mere metaphorical use of the term, by positioning the tactile experience within the broader frame of embodied cognition and the experiential turn in cognitive science. This article explores the possible contribution of a science of touch by defining music as a vibrational phenomenon that affects the body and the senses. It takes as a starting point the clinical findings on the psychological and physiological value of tender touch with a special focus on the method of kangaroo mother care, which is a method for holding the baby against the chest of the mother, skin-to-skin. It is seen as one of the most basic affiliative bondings with stimuli that elicit reward. Via an extensive review of the research literature, it is questioned as to what extent this rationale can be translated to the realm of music. There are, in fact, many analogies, but a comprehensive theoretical framework is still lacking. This article aims at providing at least some preparatory groundwork to fuel more theorizing about listening and its relation to the sense of touch.
Citation: Acoustics
PubDate: 2024-01-01
DOI: 10.3390/acoustics6010003
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 65-82: Experimental Prediction Method of
Free-Field Sound Emissions Using the Boundary Element Method and Laser
Scanning Vibrometry
Authors: Andreas Wurzinger, Florian Kraxberger, Paul Maurerlehner, Bernhard Mayr-Mittermüller, Peter Rucz, Harald Sima, Manfred Kaltenbacher, Stefan Schoder
First page: 65
Abstract: Acoustic emissions play a major role in the usability of many product categories. Therefore, mitigating the emitted sound directly at the source is paramount to improve usability and customer satisfaction. To reliably predict acoustic emissions, numerical methods such as the boundary element method (BEM) are employed, which allow for predicting, e.g., the acoustic emission into the free field. BEM algorithms need appropriate boundary conditions to couple the sound field with the structural motion of the vibrating body. In this contribution, firstly, an interpolation scheme is presented, which allows for appropriate interpolation of arbitrary velocity data to the computational grid of the BEM. Secondly, the free-field Helmholtz problem is solved with the open-source BEM software framework NiHu. The forward coupling between the device of interest and BEM is based on the surface normal velocities (i.e., a Neumann boundary condition). The BEM simulation results are validated using a previously established aeroacoustic benchmark problem. Furthermore, an application to a medical device (knee prosthesis frame) is presented. Furthermore, the radiated sound power is evaluated and contextualized with other low-cost approximations. Regarding the validation example, very good agreements are achieved between the measurements and BEM results, with a mean effective pressure level error of 0.63 dB averaged across three microphone positions. Applying the workflow to a knee prosthesis frame, the simulation is capable of predicting the acoustic radiation to four microphone positions with a mean effective pressure level error of 1.52 dB.
Citation: Acoustics
PubDate: 2024-01-03
DOI: 10.3390/acoustics6010004
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 83-96: Computational and Theoretical
Investigation of Acoustical and Vibrational Properties of Rigid Thin
Material
Authors: Haydar Aygun
First page: 83
Abstract: A computational and theoretical investigation of acoustical and vibrational properties of rigid thin fiberglass material was carried out for different boundary conditions. Fiberglass materials could be applied in industries varying from the aircraft and automotive sectors to the built environment and construction sectors. Plate vibration and acoustic radiation were applied to predict the deflection of the thin fiberglass material and sound radiation efficiency at different locations on its surface, while a study-controlled equation of motion known as the Kirchhoff thin plate theory was applied for a COMSOL simulation of the thin material to determine the deflection of the plate and to obtain stress distribution, velocity contour, displacement, and acoustic pressure at the first resonance of the material. The results of this paper show that thin fiberglass material could be applied to sandwich building elements to form panels for reducing airborne noise and to lessen the sound transmission of structural borne noise, to cover noise barriers to make them more sustainable and weather resistant, to dampen the vibration of machines, and to reduce the structural vibration of buildings.
Citation: Acoustics
PubDate: 2024-01-16
DOI: 10.3390/acoustics6010005
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 97-113: Recording, Processing, and Reproduction
of Vibrations Produced by Impact Noise Sources in Buildings
Authors: Franz Dolezal, Andreas Reichenauer, Armin Wilfling, Maximilian Neusser, Rok Prislan
First page: 97
Abstract: Several studies on the perception of impact sounds question the correlation of standardized approaches with perceived annoyance, while more recent studies have come to inconsistent conclusions. All these studies neglected the aspect of whole-body vibrations, which are known to be relevant for the perception of low-frequency sound and can be perceived especially in lightweight constructions. Basically, the contribution of vibrations to impact sound annoyance is still unknown and could be the reason for the contradictory results. To investigate this aspect, we measured vibrations on different types of floors under laboratory conditions and in situ. For this purpose, a vibration-sensing device was developed to record vibrations more cost-effectively and independently of commercial recording instruments. The vibrations of predefined impact sequences were recorded together with the sound field using a higher-order ambisonics microphone. In addition, a vibration exposure device was developed to expose the test objects to the exact vibrations that occur in the built environment. The vibration exposure device is integrated into the ambisonics reproduction system, which consists of a large number of loudspeakers in a spherical configuration. The article presents the development and performance achieved using the vibration-sensing unit and the vibration exposure device. The study is relevant for conducting future impact sound listening tests under laboratory conditions, which can be extended to include the reproduction of vibrations.
Citation: Acoustics
PubDate: 2024-01-17
DOI: 10.3390/acoustics6010006
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 114-133: Wooden Rehearsal Rooms from the
Construction Process to the Musical Performance
Authors: Maria Cairoli
First page: 114
Abstract: Rehearsal rooms play an important role in musicians’ activities to obtain the best results during a performance in front of an audience. Numerous rehearsal rooms are located in complex buildings, such as opera houses and cultural centers, where new research outcomes have led to increasingly complex projects and construction phases. Furthermore, technical complexity has also increased due to the large quantity of used materials and the innovation level of the process. In this context, a new methodology becomes mandatory to control the indoor air quality and the acoustic quality in rehearsal rooms. This paper aims to offer a procedure for rehearsal rooms for large ensembles during the construction and life cycle phases to optimize the indoor environmental quality according to different types of ensembles and repertoires. In particular, rehearsal rooms with wood panel cladding are considered. The proposed methodology is controlled by a digital twin (DT) based on building information modeling (BIM), integrated with acoustic measurements, sensors and actuators aimed at implementing the database in real time. A case study is presented, in which the cladding system is described, the new methodology is applied, and the results are compared with the criteria suggested in the standard ISO 23591.
Citation: Acoustics
PubDate: 2024-01-27
DOI: 10.3390/acoustics6010007
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 134-156: Comparing the Performance of Robust
Controllers for Vibration Suppression in Long Rotor Systems
Authors: Majid Aleyaasin
First page: 134
Abstract: In this paper, the vibration control of the multivariable model of rotor bearing systems is considered for investigation. Some simply structured controllers that can suppress vibrational disturbances are tested for their robustness via the H∞ optimality criteria. Initially, intelligent optimisation techniques are used to minimize the H∞ mixed-sensitivity norm of the Linear Fractional Transformation (LFT) of the simple two-term PI controllers acting on the rotor system models. This results in some controllers that can suppress the vibration but with a slow oscillatory response. After this, an appropriate interpretation of the Bode plot singular values of the combined sensitivity and control effort matrix is used to explain the performance shortcomings of this controller. Moreover, the existing simply structured controllers in the literature exhibiting a faster performance are examined by using singular value plots. It is shown that when the maximum singular value of the control effort matrix drops below the 0 db line, the performance will be boosted. Finally, the H∞ controllers are designed by using the robust control toolbox in MATLAB. This resulted in rapid disturbance rejection, with the vibration amplitude diminishing to zero after 0.3 s due to double-step disturbances. However, these controllers in the frequency domain have an order of eight and may not be realizable to be implemented in practice. It is concluded that examining the Bode plot of the maximum singular value of the control effort matrix is a useful tool for evaluating performance in the frequency domain. However, designing robust controllers by toolboxes in the time domain can lead to superb performance with higher-order controllers.
Citation: Acoustics
PubDate: 2024-02-01
DOI: 10.3390/acoustics6010008
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 157-176: An Investigation into the Physical
Mechanisms of Leak Noise Propagation in Buried Plastic Water Pipes: A Wave
Dynamic Stiffness Approach
Authors: Oscar Scussel, Michael J. Brennan, Jennifer M. Muggleton, Fabrício C. L. de Almeida, Phillip F. Joseph, Yan Gao
First page: 157
Abstract: In buried plastic water pipes, the predominantly fluid-borne wave is of particular interest, as it plays a key role in the propagation of leak noise. Consequently, it has been studied by several researchers to determine the speed of wave propagation and its attenuation with distance. These features are encapsulated in the wavenumber. By examining the factors that govern the behaviour of this wavenumber, this paper presents an in-depth examination of the physical mechanisms of leak noise propagation. To achieve this, an alternative physics-based model for the wavenumber is developed, using the concept of the wave dynamic stiffnesses of the individual components within the pipe system, i.e., the water in the pipe, the pipe wall, and the surrounding medium. This facilitates a clear interpretation of the wave behaviour in terms of the physical properties of the system, especially the interface between the pipe and the surrounding medium, which can have a profound influence on the leakage of acoustic energy from the pipe wall into the external medium. Three systems with different types of surrounding medium are studied, and the factors that govern leak noise propagation in each case are identified. Experimental results on two distinct test sites from different parts of the world are provided to validate the approach using leak noise as an excitation mechanism.
Citation: Acoustics
PubDate: 2024-02-01
DOI: 10.3390/acoustics6010009
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 177-203: Machine Noise—Experimental Study
of the Local Environmental Correction for the Emission Sound Pressure
Level
Authors: Fabian Heisterkamp
First page: 177
Abstract: Determining reliable noise emission values for machinery is key to successfully implement the Sell and Buy Quiet concept. ISO 11202 is a basic noise emission standard to determine the emission sound pressure level of machines outside of special acoustic test rooms (in situ measurements) and enables machinery manufacturers to determine the noise emission data of their products within their own premises. However, a recent amendment to this standard was made on the basis of an unsatisfactory amount of experimental data. Therefore, this paper systematically examines the validity and accuracy of the amended part of the method. It answers the question, whether the amendment represents an improvement of the existing method. Measurements on a model machine with two configurations allow for an extensive investigation of the effects of the amendment. To that end, the emission sound pressure levels at eight positions near the machine are determined in three different acoustic environments. One finds that the amendment leads to an overestimation of the local environmental correction for the LpA, which, in turn, could lead to an underestimation of the determined emission sound pressure level.
Citation: Acoustics
PubDate: 2024-02-08
DOI: 10.3390/acoustics6010010
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 204-218: Matched Filter for Acoustic Emission
Monitoring in Noisy Environments: Application to Wire Break Detection
Authors: Alexander Lange, Ronghua Xu, Max Kaeding, Steffen Marx, Joern Ostermann
First page: 204
Abstract: Regular inspections of important civil infrastructures are mandatory to ensure structural safety and reliability. Until today, these inspections are primarily conducted manually, which has several deficiencies. In context of prestressed concrete structures, steel tendons can be susceptible to stress corrosion cracking, which may result in breakage of individual wires that is visually not observable. Recent research therefore suggests Acoustic Emission Monitoring for wire break detection in prestressed concrete structures. However, in noisy environments, such as wind turbines, conventional acoustic emission detection based on user-defined amplitude thresholds may not be suitable. Thus, we propose the use of matched filters for acoustic emission detection in noisy environments and apply the proposed method to the task of wire break detection in post-tensioned wind turbine towers. Based on manually conducted wire breaks and rebound hammer tests on a large-scale test frame, we employ a brute-force search for the most suitable query signal of a wire break event and a rebound hammer impact, respectively. Then, we evaluate the signal detection performance on more than 500 other wire break signals and approximately one week of continuous acoustic emission recordings in an operating wind turbine. For a signal-to-noise ratio of 0 dB, the matched filter approach shows an improvement in AUC by up to 0.78 for both, the wire break and the rebound hammer query signal, compared to state-of-the-art amplitude-based detection. Even for the unscaled wire break measurements originally recorded at the 12 m large laboratory test frame, the improvement in AUC still lies between 0.01 and 0.25 depending on the wind turbine noise recordings considered for evaluation. Matched filters may therefore be a promising alternative to amplitude-based detection algorithms and deserve particular consideration with regard to Acoustic Emission Monitoring, especially in noisy environments or when sparse senor networks are required.
Citation: Acoustics
PubDate: 2024-02-20
DOI: 10.3390/acoustics6010011
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 219-239: Design of Optimal Sound Absorbers Using
Acoustic Diffusers for Multipurpose Auditoriums
Authors: Domingo Pardo-Quiles, Ignacio Rodríguez-Rodríguez, José-Víctor Rodríguez
First page: 219
Abstract: The main goal of this research was to design and study the best structure, location, and shape of acoustic diffusers to be fitted on the ceilings of multipurpose auditoriums. Their absorbing properties can enhance the acoustics when installed on high ceilings, and behind suspended reflecting panels, by mitigating or nullifying specular reflections that could overcome the panels and, thus, avoiding time delay gaps exceeding 30–40 ms compared with the direct sound. For this purpose, a typical medium-sized room, with inclined floors, a stage, and 20 rows of seats, was considered. The allocation and height of the considered diffusers were based on the Schroeder quadratic residue sequence, and they were modeled as rectangles, wedges, cylinders, and Y-shaped elements. A standardized speech source spectrum was analyzed for up to five different receiver locations. In this way, the attenuation parameter as a function of frequency was evaluated and compared between the candidate diffusers in order to identify the best absorber. The simulations were undertaken with a software tool previously validated by the authors called PARDOS, which incorporates an innovative formulation based on the uniform theory of diffraction (UTD) to analyze multiple diffractions and reflections of acoustic waves. The results show that the new Y-shaped diffusers proposed, tuned for the hearing frequency band from 250 Hz up to 10,000 Hz, attained the best acoustic performance in terms of absorption.
Citation: Acoustics
PubDate: 2024-03-06
DOI: 10.3390/acoustics6010012
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 240-256: Influence of the Gain–Bandwidth of
the Front-End Amplifier on the Performance of a QEPAS Sensor
Authors: Luigi Lombardi, Gianvito Matarrese, Cristoforo Marzocca
First page: 240
Abstract: The quartz tuning fork used as an acoustic sensor in quartz-enhanced photo-acoustic spectroscopy gas detection systems is usually read out by means of a transimpedance preamplifier based on a low-noise operational amplifier closed in a feedback loop. The gain–bandwidth product of the operational amplifier used in the circuit is a key parameter which must be properly chosen to guarantee that the circuit works as expected. Here, we demonstrate that if the value of this parameter is not sufficiently large, the response of the preamplifier exhibits a peak at a frequency which does not coincide with the series resonant frequency of the quartz tuning fork. If this peak frequency is selected for modulating the laser bias current and is also used as the reference frequency of the lock-in amplifier, a penalty results in terms of signal-to-noise ratio at the output of the QEPAS sensor. This worsens the performance of the gas sensing system in terms of ultimate detection limits. We show that this happens when the front-end preamplifier of the quartz tuning fork is based on some amplifier models that are typically used for such application, both when the integration time of the lock-in amplifier filter is long, to boost noise rejection, and when it is short, in order to comply with a relevant measurement rate.
Citation: Acoustics
PubDate: 2024-03-06
DOI: 10.3390/acoustics6010013
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 257-271: Acoustic Characteristics of Greek Vowels
Produced by Adult Heritage Speakers of Albanian
Authors: Georgios P. Georgiou, Aretousa Giannakou
First page: 257
Abstract: Investigating heritage language (HL)-contact effects on the dominant language has received limited attention despite its importance in understanding the dynamic interplay between linguistic systems in situations of bilingualism. This study compares the acoustic characteristics of Greek vowels produced by heritage speakers (HSs) of Albanian and monolingual Greek speakers, aiming to identify potential differences and explain them. The participants were adult second-generation HSs of Albanian with Greek as their dominant language, born and raised in Greece. A control group of age-matched monolingual Greek speakers was included for comparison purposes. All participants engaged in a controlled speech production task, with the data segmented to extract acoustic values pertaining to the first three formants and the duration of Greek vowels. Bayesian regression models were employed for the subsequent statistical analysis. The results demonstrated differences in the first three formants of certain vowels and the duration of all vowels. These differences can be attributed to the crosslinguistic effect of HL on the dominant language, as well as the interplay between the dynamic and internalized language system of the speakers and the complex effect of the sociophonetic context. These outcomes contribute to the hypothesis positing the emergence of deflected phonetic categories among a distinctive group of bilinguals, namely HSs. Furthermore, this study underscores the significance of a comprehensive exploration of the sociophonetic context of HSs for a nuanced understanding of their phonetic patterns.
Citation: Acoustics
PubDate: 2024-03-10
DOI: 10.3390/acoustics6010014
Issue No: Vol. 6, No. 1 (2024)
- Acoustics, Vol. 6, Pages 272-297: Performance Evaluation of Balcony
Designs for Mitigating Ground Level Noise
Authors: Long Bin Tan, Linus Yinn Leng Ang
First page: 272
Abstract: This study aims to tackle the challenge of high noise levels on balconies while preserving natural ventilation. Eight innovative balcony designs, incorporating elements like diffuser edges, undulating ceilings, Helmholtz resonators, grooves, or sound traps, were evaluated via finite element (FE) modeling. The insertion loss results showed that for many balcony designs, noise reduction in the balcony could deteriorate beyond an elevation of 8 m. However, the front jagged and full wavy ceiling designs were shown to be more robust in noise attenuation across balconies on different floors. The jagged ledge and grooved parapet designs yielded an overall 1.5 dBA lower SPL at the exterior regions, compared to other designs, which implies that the designs are less acoustically detrimental to nearby residential blocks as they tend to diffract and absorb incident noise. The jagged ledge design is more effective for lower floors while the jagged ceiling design is more effective for higher floors. A combination of the protruded jagged ledge for the lower floor and jagged balcony ceiling for the higher floor would result in the lowest noise ingress over three stories of residential units: this would be capable of achieving more than 3 dB noise reduction and would offer viable options for improving balcony noise mitigation, by providing valuable insights to architects and designers seeking practical solutions for outdoor noise reduction. Our study highlights that whereas the spectrum characteristics of acoustic absorption materials may be less tunable, and where reduced head space is traded for thicker material for greater ab-sorption and added affixation and maintenance cost, the jagged ledge and ceiling curvatures can actually be shape-tuned, say for every 3 to 4 floors up the high-rise to more effective reduce noise ingress and possibly improve the architecture façade outlook.
Citation: Acoustics
PubDate: 2024-03-11
DOI: 10.3390/acoustics6010015
Issue No: Vol. 6, No. 1 (2024)
