Authors:Serpilli Fabio, Di Nicola Giovanni, Pierantozzi Mariano Abstract: Building Acoustics, Ahead of Print. In this paper, an alternative method for the calculation of masonry walls sound insulation is investigated. Thirty-four simple monolithic brick walls were examined. For the considered walls, the measurements made by accredited laboratories in compliance with ISO 10140 standard were collected. For each building element, the experimental measurements and all the information concerning the geometric and physical characteristics of all the components (material, dimensions, mass, density, Young’s modulus, Poisson’s module, hole content, etc.) were classified. Then, from the collection of measurements obtained in the standard laboratories and the division of them into homogeneous groups, a statistical sensitivity analysis to determine the most statistically significant parameter for the sound insulation of building walls was carried out. This analysis was a useful tool for selecting parameters to be used in forecast models and for calculating statistical effects. Finally, an alternative method based on the use of artificial neural networks (ANN) was proposed. This paper discusses the results obtained by applying the models to a specific kind of construction: the masonry walls. The results will show a good correlation of the values obtained on this first type of building construction. This encourages the extension of the method explained in this work to other types of walls. Citation: Building Acoustics PubDate: 2021-02-26T06:03:37Z DOI: 10.1177/1351010X21994462
Authors:P. Domenighini Abstract: Building Acoustics, Ahead of Print. ‘Liederistic’ music is a musical genre on which architectural acoustical research is rarely focused. Despite this lack of scholarship, however, this genre represents one of the most interesting challenges for acoustical problem solving. In fact, it combines speech and music comprehension requirements in a fascinating manner to illuminate elements of both the magnification of the musical score and the hidden tension of a sung poetry text. To individualise the main characteristics of this genre, a multidisciplinary approach is taken, starting from a musical point of view. A knowledge and comprehension of music is a fundamental step to determine the parameters that allow for the best performance and listening experience of this particular music. Consequently, an introduction to the physics and acoustical characteristics of the singing voice and the piano is given, specifically highlighting the technological development of the piano since the 18th century. Through a combination of historical, architectural, and interior design research, a possible location of the original performance is recreated to investigate the probable primal acoustic conditions using computational analysis. Various contemporary chamber music halls were then considered and compared to the reconstructed location to investigate whether actual places exist with similar acoustic conditions. Citation: Building Acoustics PubDate: 2021-02-17T10:10:17Z DOI: 10.1177/1351010X21994973
Authors:Romana Rust, Achilleas Xydis, Kurt Heutschi, Nathanael Perraudin, Gonzalo Casas, Chaoyu Du, Jürgen Strauss, Kurt Eggenschwiler, Fernando Perez-Cruz, Fabio Gramazio, Matthias Kohler Abstract: Building Acoustics, Ahead of Print. In this paper, we present a novel interdisciplinary approach to study the relationship between diffusive surface structures and their acoustic performance. Using computational design, surface structures are iteratively generated and 3D printed at 1:10 model scale. They originate from different fabrication typologies and are designed to have acoustic diffusion and absorption effects. An automated robotic process measures the impulse responses of these surfaces by positioning a microphone and a speaker at multiple locations. The collected data serves two purposes: first, as an exploratory catalogue of different spatio-temporal-acoustic scenarios and second, as data set for predicting the acoustic response of digitally designed surface geometries using machine learning. In this paper, we present the automated data acquisition setup, the data processing and the computational generation of diffusive surface structures. We describe first results of comparative studies of measured surface panels and conclude with steps of future research. Citation: Building Acoustics PubDate: 2021-02-15T04:45:02Z DOI: 10.1177/1351010X20986901
Authors:Rodrigo Scoczynski Ribeiro, Raylton Pereira de Sousa, Rosemara Santos Deniz Amarilla, Luis Henrique Sant’Ana, Márcio Avelar, Rodrigo Eduardo Catai, Adalberto Matoski Abstract: Building Acoustics, Ahead of Print. It is a well-discussed topic that Construction and Demolition Waste (CDW) can be recycled and used as aggregate in the construction sector. Generally, Brazilian construction techniques are based on hollow blocks or bricks and mortars as coating systems. This paper describes the sound insulation of a masonry wall built with hollow concrete blocks and CDW as aggregates. The measurements were performed according to the reverberant chamber method. Keeping sustainability in mind instead of applying cement mortar as coating system, Oriented Strand Boards (OSB) and Wood-Wool Cement Boards (WWCB) were used and also tested as acoustical linings. The panels were directly attached on the wall with nails in the receiving room. All types of panels increased the weighted sound reduction index ([math]). Wood-based composites can also improve the air quality because of their hygroscopic properties. In summary, sustainable wall systems were characterized according to their sound insulation properties, presented as possible substitutes for traditional masonry walls. Citation: Building Acoustics PubDate: 2021-02-13T06:57:57Z DOI: 10.1177/1351010X21993640
Authors:Maedot S. Andargie, Marianne Touchie, William O’Brien Abstract: Building Acoustics, Ahead of Print. Trends of urbanization, densification, and telework all point to increasing exposure to ambient noise for workers. With the lockdown policies implemented in response to COVID-19, a research opportunity to study perceived noise exposure for teleworking arose. This paper presents the results of a survey on noise issues in multi-unit residential buildings (MURBs) and the consequent effects on occupants' well-being and productivity during the lockdown. Responses were collected from 471 MURB occupants across Canada. The results show that, despite the decrease in environmental noise, many are annoyed by outdoor noise, particularly from traffic and construction activities, and indicated that it affects their ability to work. Effects on ability to work from home were more frequently reported for indoor noise sources particularly airborne and impact noises coming from neighboring suites. Our findings, however, show that noise coming from occupants in the same suite (i.e. roommates and family) present the biggest issue. The findings indicate that existing noise conditions in MURBs might not be suitable for a permanent large-scale implementation of teleworking. Citation: Building Acoustics PubDate: 2021-02-09T08:41:14Z DOI: 10.1177/1351010X21993742
Authors:Khaled Bataineh Abstract: Building Acoustics, Ahead of Print. This paper focuses on the development of tomography—transmission electron microscope (TEM) specimen holder stable under environment effect that allows atomic resolution. The successful holder must be dynamically stable for accuracy and image processes to obtain an atomic resolution, with a minimum controllable drift of the sample position. Different strategies to reduce the effect of acoustic disturbances are investigated. The approach to the problem has been two-fold, numerical and experimental. The effect of mechanical and acoustic noise is analyzed. Finite element results match very well previous experimental results and observations. Theoretical analysis showed that air pressure fluctuations have a significant impact on microscopes with side entry goniometers, especially when the exciting frequency matches a vibration mode of the sample holder. For example, finite element analysis (FEA) predicts that the tip deflections are 4.5 Å and 0.09 Å under air pressure excitation of 64 and 40 dB respectively. Utilizing a sandwiched constrained damping shell layer made of viscoelastic material that partially covers the inner part of TEM holder body successfully decreased the vibration. Finite element simulations predict that a shell layer of viscoelastic material with a thickness equal to the 1/10 of the body holder diameter reduces the vibrations by 30%. The viscoelastic layer shell thickness, loss factor, and elastic modulus have a strong effect on the damping behavior and the optimal combination should be determined. Citation: Building Acoustics PubDate: 2021-01-27T07:12:06Z DOI: 10.1177/1351010X21989494
Authors:Yaw-Shyan Tsay, Chuan-Hsuan Lin Abstract: Building Acoustics, Ahead of Print. Multi-layer cavity wall (MCW) systems, which refer to each panel in the structure being made up of two or more layers of lightweight board, have become more widely used. However, unlike the detailed approaches that were available for predicting single-layer cavity walls (SCW), few studies have addressed the MCW involving different layers attached together. In this research, we applied two theoretical models of SCW, analyzed the key parameters and modify to have appropriate application for MCW. The predictive capability of the models was then evaluated by comparing them with results of experiment and commercial software. The results showed that Sharp’s model was suggested only when the thickness of the steel stud of about 0.75 mm. Through modifying the input values of the compliance of steel (CM), attenuation factor (F) and the limiting angle of incident (θL) in Davy’s model, and the prediction of the proposed model showed great consistent with experiments. Citation: Building Acoustics PubDate: 2021-01-18T07:56:27Z DOI: 10.1177/1351010X20987355
Authors:Marco Berzborn, Michael Vorländer Abstract: Building Acoustics, Ahead of Print. The analysis of the spatio-temporal features of sound fields is of great interest in the field of room acoustics, as they inevitably contribute to a listeners impression of the room. The perceived spaciousness is linked to lateral sound incidence during the early and late part of the impulse response which largely depends on the geometry of the room. In complex geometries, particularly in rooms with reverberation reservoirs or coupled spaces, the reverberation process might show distinct spatio-temporal characteristics.In the present study, we apply the analysis of directional energy decay curves based on the decomposition of the sound field into a plane wave basis, previously proposed for reverberation room characterization, to general purpose performance spaces. A simulation study of a concert hall and two churches is presented uncovering anisotropic sound field decays in two cases and highlighting implications for the resulting temporal evolution of the sound field diffuseness. Citation: Building Acoustics PubDate: 2021-01-04T12:15:30Z DOI: 10.1177/1351010X20984622
Authors:Ajish K Abraham, M S Ravishankar Abstract: Building Acoustics, Ahead of Print. High reverberation times (RTs) have always been an acoustic barrier to effective learning in classrooms. Acoustic corrections to reduce RT involve complex acoustic treatment. Previous studies have indicated that classrooms in most schools do not meet the established acoustic criteria, as the school authorities refrain from such acoustic treatment. Aim of the study was to optimize the RT within classrooms through easily-implementable acoustic corrections. Different combinations of acoustic corrections have been experimented in eight classrooms, through a step-by-step approach to optimize RT. After each acoustic modification, the RT was measured and the speech clarity parameter C50, was estimated. At the final step, RT of the classrooms was diminished to a mean value of 0.74 s (standard deviation = 0.04) from the initial mean value of 4.37 s (standard deviation = 0.42). C50 values corresponding to the final acoustic correction were found to fall within good speech intelligibility scale. Citation: Building Acoustics PubDate: 2020-11-25T06:10:36Z DOI: 10.1177/1351010X20975765
Authors:Javier Sanz Soriano, Oliver Wright, Elisabeth van den Braak, Christopher Day Abstract: Building Acoustics, Ahead of Print. Traditional ray tracing software tools (e.g. Odeon, CATT-Acoustic, EASE) enable detailed analysis of stage acoustics; however, they are typically undertaken in later design stages and lack the flexibility required for early design development. This paper, which follows from a poster presentation at ISRA 2019, investigates the use of a three-dimensional modelling platform (Rhinoceros/Grasshopper) to quickly assess the influence of architectural changes on reflections that support orchestral ensemble. This approach enables immediate feedback, a more creative design process and better integration of architecture and acoustics. Early reflections have been found to be vital for effective orchestral ensemble. Therefore, the study focused on the investigation of early energy distribution on stage with ray tracing analysis using a parametric tool. This tool also considers cross-stage shielding effects from the orchestra and the directivity of instruments. The results of the tool have been compared to an existing acoustic modelling software to determine its accuracy and reliability. Additionally, the expansion of the tool with an evolutionary solver has also been explored. The development of a Rhinoceros/Grasshopper design tool has been found to be beneficial in the analysis of stage conditions and enhances the design collaboration during early design phases. Citation: Building Acoustics PubDate: 2020-11-20T06:36:43Z DOI: 10.1177/1351010X20971102
Authors:Yann Jurkiewicz, Henrik Moller, Thomas Wulfrank, Jingbo Wang, Eckhard Kahle Abstract: Building Acoustics, Ahead of Print. Curved surfaces are increasingly part of the architectural language used in buildings for the performing arts, yet have known challenges both in reality and in ray-tracing-based computer simulations. The designs of the 1000-seat symphony hall, the 1600-seat opera house and the 800-seat multi-purpose hall in Fuzhou, China, were all based on curved surfaces, both convex and concave, often covered with local ceramic tiles. Providing the right amount, distribution and quality of early reflections thus required a precise analysis of the acoustic behavior of curved surfaces. The acoustic design interacted with the architecture in precisely shaping those curves in 3D. In order to explore the acoustic potential and detect problems related to the architectural concept of both rooms, novel geometrical acoustics analysis algorithms were developed within NURBS modeling software rather than relying on commercial ray-tracing algorithms. Optimization of the curved surfaces is obtained when the output of these algorithms, the interpretation of the acoustic consultant, and the required integration of acoustic solutions within the global architectural concept are all aligned – a “meeting of minds” between acoustics and architecture. The analysis procedure and geometrical acoustics algorithms used will be presented in detail, as well as the related decision-making process, the acoustic predictions and the measurement results of the three built halls. Citation: Building Acoustics PubDate: 2020-11-10T09:49:24Z DOI: 10.1177/1351010X20968714
Authors:Giuseppe Ciaburro, Umberto Berardi, Gino Iannace, Amelia Trematerra, Virginia Puyana-Romero Abstract: Building Acoustics, Ahead of Print. The catacombs, burial sites for early Christians, were constructed during the Roman Empire until the Christian religion was recognized in 313 AD. The catacombs were cementeries, which were organized according to precise rules and were dug into the ground on several levels, to occupy as little space as possible. The catacombs became places of worship as martyrs were buried in them. The catacombs were then abandoned with the barbarian invasions and the consequent construction of churches inside cities. The catacombs were rediscovered during the Renaissance period and became a place of renewed worship. In the present work, the acoustic characteristics of the catacombs of San Callisto in Rome, San Gennaro in Naples, and Vigna Cassia in Syracuse are discussed. The three selected catacombs differ by type of excavation and geometry. In particular, the catacombs of San Callisto are made of narrow corridors and small rooms; the catacombs of San Gennaro consist of large rooms with niches; the catacombs of Vigna Cassia are partly excavated in the tuff and partially occupy a disused aqueduct. The acoustic measurements were performed using an impulsive sound source. The description of the acoustic characteristics focuses on the reverberation time and the Speech Transmission Index. The results show that the reverberation time was always shorter than 1 second, confirming the reduced reverberation of these environments. Finally, the speech listening characteristics are particularly good, ensuring the suitable conditions for the prayer in these spaces. Citation: Building Acoustics PubDate: 2020-10-28T10:36:17Z DOI: 10.1177/1351010X20967571
Authors:Louena Shtrepi, Tomás Mendéz Echenagucia, Elena Badino, Arianna Astolfi Abstract: Building Acoustics, Ahead of Print. Different numerical techniques have been used in the last decades for the acoustic characterization and performance optimization of sound diffusive surfaces. However, these methods require very long calculation times and do not provide a rapid feedback. As a result, these methods can hardly be applied by designers at early stages of the design process, when successive design iterations are necessary from an aesthetic point of view. A suitable alternative could be the use of parametric modeling in combination with performance investigations during the design process of sound diffusive surfaces. To this aim, this study presents a design process for diffusive surfaces topology optimization based on the combination of parametric models and geometrical acoustic simulations. It aims to provide architects and designers with rapid visual feedback on acoustic performances at a preliminary stage of the design process. The method has been tested on different case studies, which have been modelled based on geometric guidelines for diffusive surface optimization. The sensitivity of the method showed that it could be a very useful tool for comparisons among surface design alternatives. Finally, the advantages and limitations of the integrated optimization in comparison with conventional optimizations are discussed. Citation: Building Acoustics PubDate: 2020-10-28T10:35:47Z DOI: 10.1177/1351010X20967821
Authors:Marco A Oliveira, Luis Bragança, Sandra M Silva, Dinara Paixão, Julieta António Abstract: Building Acoustics, Ahead of Print. Acoustic comfort and indoor air quality are essential for the health and wellbeing of the occupants of the building. Thus, the façade must guarantee enough sound insulation and ventilation conditions. However, these aspects conflict because opening windows or using ventilation openings reduces the sound insulation of the envelope and allows the exterior noise entrance. To limit noise transmission into the building, ventilators use passive, active or hybrid noise control techniques. This work addresses the noise reduction performance of a mechanical ventilator for façades, evaluating the effect of different options of passive noise control strategies in the sound insulation of the proposed ventilator. In addition, the air change rate and energy consumption of the ventilator were also investigated. Three prototypes were fabricated and tested at an acoustic chamber, along with ventilation tests carried out in a room equipped with a blower door. CFD simulations were used to enhance the aeraulic geometry of the prototypes, prior to its fabrication. The acoustic experiments showed Dn,e,w values up to 55 dB and noise emission levels lower than 25 dB(A). The use of resistive sound absorbers proved to be more effective in mitigating noise than reactive absorbers, over the entire frequency range. The ventilation tests revealed air change rates of 3.7 h−1 at 50 Pa, while the ventilator’s annual energy consumption was 17.52 kWh. The results highlight the proposed device as a viable alternative for decentralised mechanical ventilation, capable of ensuring noise protection and satisfactory ventilation rates, under a sustainable perspective of minimum energy demand. Citation: Building Acoustics PubDate: 2020-10-26T06:29:32Z DOI: 10.1177/1351010X20966185
Authors:Anders Homb, Simone Conta, Christoph Geyer, Niko Kumer Abstract: Building Acoustics, Ahead of Print. The industrialisation of timber buildings has improved strongly in recent years. When long span is required, timber hollow-box floor elements are increasingly used due to their structural performance. The aim of this paper is to assess the acoustic performance of timber hollow-box floors, determine the governing parameters and identify the corresponding trends. We collected results from laboratory measurements covering both airborne and impact sound insulation from four different laboratories covering a wide range of application. Data include the bare floor constructions and their combination with different floating floors including both lightweight solutions and hybrid solution. We performed the analysis focusing on following parameters: element stiffness, element mass per unit area, dynamic stiffness of the resilient layer, cavity filling and floating floor material. We present the collected data both frequency-dependent and as single number quantities. General trends and features are identified in the frequency-dependent diagrams. A further detailed analysis is based on the single number quantities. It includes a general relationship between element mass per unit area and given requirements for R’W + C50-5000 and L’n,w + CI,50-2500. Furthermore, diagrams are presented illustrating the dependence of impact sound insulation numbers on the cavity filling, the dynamic stiffness of the resilient layer and the type of material used for the floating floor. The additional mass in the cavity improves both airborne and impact sound insulation by minimum 10 dB. This, combined with a floating floor, allows the fulfilment of a wide range of requirements. Citation: Building Acoustics PubDate: 2020-10-24T07:31:18Z DOI: 10.1177/1351010X20966157
Authors:Eric Brandão, Gonçalo Morgado, William D’A Fonseca Abstract: Building Acoustics, Ahead of Print. This paper presents a ray tracing algorithm developed as a research and teaching tool. The motivations to pursue this task and some novel features of the algorithm are presented. Amongst them, it is possible to cite: (i) the receivers may grow in size, which saves some computational cost; (ii) sound intensity calculations are performed in a separate step than geometrical ray tracing; and (iii) those features allow Monte Carlo simulations for uncertainty prediction related to absorption data. The results obtained with the proposed algorithm are compared with the measured data (and other software packages) of Round Robins II (Elmia Hall) and III (PTB recording studio) and proved to be in good agreement with measured data. The ratio of the mean error by the JND of each parameter are compatible with the results presented by the other round robin participants. The product of this research is also scalable to an hybrid algorithm and alternatives to do so are provided through the discussion in the paper. Citation: Building Acoustics PubDate: 2020-10-21T05:02:41Z DOI: 10.1177/1351010X20964758
Authors:Gustavo Basso Abstract: Building Acoustics, Ahead of Print. The “Blue Whale” Auditorium in Buenos Aires opened in 2015. Designed to be the headquarters of the National Symphony Orchestra of Argentina, its goal was to become the city’s main space for symphonic music. The architectural program posed several challenges from an acoustic point of view, as 2000 people had to be accommodated in a square space into which none of the usual architectural typologies fit properly. It was decided, therefore, to place in this space an “ad-hoc” hall. The design centered around three main premises: to achieve an enveloping acoustic field, to establish an adequate reverberation decay, and to combine reflective and diffusing surfaces to attain a similar acoustic field through the entire audience area. This work details the design process of the Auditorium, during which the final shape was deduced from the established acoustic premises, and some acoustical measurements made in the finished hall. Citation: Building Acoustics PubDate: 2020-09-28T12:42:49Z DOI: 10.1177/1351010X20959261
Authors:Giuseppe Ciaburro, Gino Iannace, Amelia Trematerra, Ilaria Lombardi, Maurizio Abeti Abstract: Building Acoustics, Ahead of Print. This paper discusses the acoustic characteristics of the “Dives in Misericordia” Church in Rome. The church was designed by architect Richard Meier and opened in 2003. It was made entirely of white concrete and consists of three septa with a double curve shaped like a sail. The nave roof is glass. The volume is approximately 14.000 cubic meters. The highest measuring is approximately 26 m. the width of the nave is 19.5 m, while the maximum width is 29.5 m, while the internal length is 32.0 m, while the total length is 45.6 m. It can seat approximately 240 people. The acoustic measurements were taken by placing a microphone at different points of the nave (the area occupied by the audience), with the sound source being placed on the altar. It was therefore possible to obtain a spatial distribution of the average acoustic characteristics inside the church. At a frequency of 1000 Hz, the average values of the reverberation time is about 10 s. In its current configuration, the church is neither suitable for understanding speech nor listening to music. A 3D virtual model was created and with the help of the building acoustics software it was possible to study the sound field inside the church. The possibility to carry out an appropriate acoustic correction was analyzed, in order to reduce the values of the reverberation time, by pacing on a side wall of the church an adequate number of sound-absorbing polyester panels. Citation: Building Acoustics PubDate: 2020-08-08T09:03:45Z DOI: 10.1177/1351010X20948653
Authors:Feng Yan, Robin Wilson, Peter Rutherford Abstract: Building Acoustics, Ahead of Print. Energy transmission across lightly damped structures has been well studied including the approved success of statistical energy analysis in mid and high frequency bands. For heavily damped elements, the diffuse field theory, which is used in computing coupling loss factors, tends to fail. Energy attenuation with distance becomes more significant for such elements and hence the energy is less likely to be evenly distributed within those elements. A ray tracing algorithm is developed taking account of this phenomenon by tracking the travel history of a great number of discrete rays. The predicted transmitted energy is used in a modified statistical energy analysis model to calculate energy level difference between different subsystems. Numerical validation and comparison on a concrete five-plate system are conducted in both lightly damped and heavily damped cases. Both the classic and the hybrid models show good agreement for lightly damped system and differ for heavily damped system. The difference tends to become larger with increasing frequency and internal damping level. The parameter “effective length ratio” is proposed to describe the phenomena of energy concentration along the edge and as in indicator of whether the application of diffuse field theory is appropriate. Citation: Building Acoustics PubDate: 2020-07-15T09:53:47Z DOI: 10.1177/1351010X20939553
Authors:Zakariyya Uzeyirli, Aslı Özçevik Bilen Abstract: Building Acoustics, Ahead of Print. The inclusive education method has substantial contributions to hearing-impaired individuals’ education and socialization. However, the poor physical environment and acoustic comfort conditions negatively affect speech intelligibility at such places and therefore, the quality of education. Upon determining that there are very few subjective evaluation studies, we conducted a study regarding the impact of acoustic comfort conditions on speech intelligibility at inclusive education places. Within the scope of the study, first, a classroom was determined, and the current acoustic conditions of the class were evaluated objectively by field acoustic measurements. A calibrated model was created in the simulation software of the relevant class and then two more models with optimum reverberation time values of 0.4 s and 0.8 s as suggested in the literature, and auralizations were performed for the models. For subjective evaluation, a subject group of hearing-impaired and normal hearing individuals fulfilling equal conditions were tested by speech discrimination test in real-time in the classroom and from auralization recordings in a laboratory setting. Regarding the results obtained, it was observed that speech intelligibility percentage of normal hearing individuals increased as expected while in hearing-impaired individuals, contrary to the expectations, percentage differed from one another, and there was no increase. Following the discussions with experts, it was concluded that different hearing aids used by hearing-impaired individuals might lead to this situation. Accordingly, it occurs that the possibility to achieve a good speech intelligibility for hearing-impaired individuals even if optimum acoustic values suggested are fulfilled in education places remains unclear. Citation: Building Acoustics PubDate: 2020-07-02T10:51:40Z DOI: 10.1177/1351010X20923581
Authors:Gino Iannace, Giuseppe Ciaburro Abstract: Building Acoustics, Ahead of Print. Plastic is widely used all over the world and its production has been increasing continuously in recent years. But plastic presents significant problems about its end-of-life given its important environmental impact. These problems impose recycling policies which provide for the collection and recycling of plastic materials. In this work, the acoustic properties of a recycled polyethylene terephthalate-based material were analyzed. The material showed good sound-absorbing characteristics, especially at high frequencies. In addition, a numerical model based on the Gaussian regression was developed to simulate the sound absorption coefficient of the material. The model returned an R-Squared value of 0.97 demonstrating excellent performance. Citation: Building Acoustics PubDate: 2020-06-15T11:31:30Z DOI: 10.1177/1351010X20933132
Authors:Chiung Yao Chen Abstract: Building Acoustics, Ahead of Print. The aim of this study was to verify what statistical attributes are effective descriptors of time-varying noise levels due to road traffic and complex medical routine activities in hospital lobbies. In a psychoacoustic experiment, respondents provided perceived noisiness ratings affected by 12 noise events in hospital lobbies according to the processes recommended by ISO 15666. According to the correlations between subjective and objective survey results, the average LAeq ,15 m induced during the daytime itself was confirmed to be poorly related to subjective noisiness. The three independent variables shown to have the largest effects on perceived noisiness were (1) L min − L max, (2) the effective duration of the normalized autocorrelation function (τe, h) of all LAeq,15 m from 9:00 a.m. to 5:00 p.m., and (3) the gradient of the cumulative distribution function (0.3–0.7 cumulative rate range). These statistical attributes have been confirmed as useful tools for detecting perceptions of complicated noise sources, but the associated correlations cannot be recovered from the relevant previous studies. Finally, construction noise was confirmed by factor analysis to be the accidental noise source with the highest factor loading (0.779) but a lower variance ( Citation: Building Acoustics PubDate: 2020-06-12T09:34:53Z DOI: 10.1177/1351010X20919868
Authors:Jörgen Olsson, Andreas Linderholt Abstract: Building Acoustics, Ahead of Print. Traditionally, product development concerning acoustics in the building industry is measurement oriented. For lightweight floors, frequencies that are lower than the frequency range for heavy concrete floors are an issue. The frequency range of from 50 Hz down to 20 Hz influences the human perception of impact sound in multi-story apartment buildings with lightweight floor constructions, such as timber floors, for example. It is well known that a lower frequency range of interest makes finite element simulations more feasible. Strategies for reducing impact sound tend to be less straightforward for timber floors because they have a larger variation of designs when compared to concrete floors. This implies that reliable finite element simulations of impact sound can save time and money for the building industry. This study researches the impact sound transmission of lightweight timber floors. Frequency response functions, from forces on excitation points to sound pressure in the receiving cavity below, are calculated. By using fluid elements connected to reflection-free boundary elements under the floors in the models, the transmission and insulation can be studied without involving reverberation. A floor model with a hard screed surface will have a larger impact force than a softer floor, although this issue seems less pronounced at the lowest frequencies. To characterize floor surfaces, the point mobilities of the impact points are also calculated and presented. The vibration and sound transmission levels are dependent on the selection of the excitation points. Citation: Building Acoustics PubDate: 2020-06-01T11:09:40Z DOI: 10.1177/1351010X20917874
Authors:Nicola Granzotto, Chiara Scrosati, Fabio Scamoni, Edoardo A Piana Abstract: Building Acoustics, Ahead of Print. Gypsum board walls are widely used in today’s buildings. A possible way to considerably increase the sound insulation performances of such lightweight walls is to apply double-layer gypsum panels screwed together. Being the boards separated by a thin air gap, there is no shift of the critical frequency from the single-layer case. Moreover, it is possible to obtain an improvement of the sound insulation performances provided by the additional mass given by the double layer. The thin air layer is, however, responsible for a loss of acoustic performance due to the cavity resonance effect in the frequency range between 800 and 1600 Hz. In this article, the increase in the acoustic insulation achieved through the use of coupled gypsum boards is studied and a modelling technique based on the transfer matrix method is used to simulate the acoustic behaviour of the resulting structure; in particular, the thin air layer between the coupled boards is modelled. The simulations are compared with laboratory measurements carried out according to the international standard series ISO 10140. The transfer matrix approach is found to be suitable to describe the problem, provided that a modified model for the air gap between the boards is applied. Citation: Building Acoustics PubDate: 2020-05-27T09:13:36Z DOI: 10.1177/1351010X20921038
Authors:Gino Iannace, Giuseppe Ciaburro, Amelia Trematerra Abstract: Building Acoustics, Ahead of Print. In this study, the data obtained from the acoustic measurements were used to train a model based on logistic regression in order to detect a quadrotor’s vehicle in indoor environment. To simulate a real environment, we made sound recordings in a shopping center. The sounds related to two scenarios were recorded: only anthropic noise and anthropic noise with background music. Later, we reproduced these sounds in an indoor environment of the same size and characteristics as the shopping center. During the simulation test, a drone placed at different distances from the sound level meter was turned on at different speeds to identify their presence in complex acoustic scenarios. Subsequently, these measurements were used to implement a model based on logistic regression for the automatic detection of the unmanned aerial vehicle. Logistic regression is widely used in pattern recognition of the binary dependent variable. This model returns high value of accuracy (0.994), indicating a high number of correct detections. The results obtained in this study suggest the use of this tool for unmanned aerial vehicle detection applications. Citation: Building Acoustics PubDate: 2020-05-13T10:49:05Z DOI: 10.1177/1351010X20917856
Authors:Hui Xie, Bingzhi Zhong, Chang Liu First page: 283 Abstract: Building Acoustics, Ahead of Print. Recent studies have investigated sound environment in nursing homes. However, there has been little research on the sound environment of nursing units. This research sought to address this gap. Subjective evaluations were gathered using questionnaire surveys of 75 elderly residents and 30 nursing staff members in five nursing units of five nursing homes in Chongqing, China. Background noise level and reverberation time were measured in five empty bedrooms, five occupied bedrooms and five occupied nursing station areas, in five nursing units. The subjective evaluation results indicate that the residents stay in the nursing units for most of their waking hours. The residents and nursing staff had strong preferences for natural sounds, with the lowest perceptions of these in the nursing units. The background noise level in all the occupied bedrooms exceeded Chinese standards for waking and sleeping hours. Only 20% of the occupied nursing station areas were below the allowable noise level for recreation and fitness room during sleeping hours. The nursing station area was identified as the main source of noise in the unit during waking hours. The average background noise level of the occupied bedrooms was 3–12 dBA higher than that of the empty bedrooms during sleeping hours. Attention should be given to the implementation of noise specifications for sleeping hours. The reverberation time of the bedrooms was within the range of 0.44–0.68 s, and in the nursing station areas it was 0.63–1.54 s. Citation: Building Acoustics PubDate: 2020-04-17T10:24:22Z DOI: 10.1177/1351010X20914237
Authors:Thomas Hulland, Andy Su, Michael Kingan First page: 299 Abstract: Building Acoustics, Ahead of Print. This article describes an investigation into the noise levels which patients are exposed to in a general inpatient hospital ward in New Zealand. An initial noise survey was conducted over a period of nine consecutive days in order to establish the noise levels in the ward. It was identified that noise levels increased dramatically between 4:00 a.m. and 7:00 a.m. In order to identify the sources of noise during this period, three noise surveys were undertaken between 4:30 a.m. and 7:00 a.m. on typical weekdays using a microphone placed inside a shared bedroom. During the noise survey, an observer identified the noise sources and their locations for significant noise events. Noise sources were then categorised into three main groups based on the character of the source (machine, staff or patient). Staff noise was found to account for 64% of the total duration of significant noise events (29% of the number of events) which occurred during the observations compared with 20% from patients (43% of the number of events) and 16% from machines (28% of the number of events). It was found that many staff and machine noise events could be mitigated or eliminated. Methods for mitigating noise are suggested and an experimental method was used to estimate the likely reduction in noise which could be attained by moving a staff conversation from the corridor outside the observed bedroom to other locations on the ward. Citation: Building Acoustics PubDate: 2020-05-07T06:49:58Z DOI: 10.1177/1351010X20916120
Authors:Lamberto Tronchin, Francesca Merli, Massimiliano Manfren, Benedetto Nastasi First page: 311 Abstract: Building Acoustics, Ahead of Print. During the renovation of auditoria and concert halls, the acoustic quality is normally evaluated from measurements of impulse responses. One possibility for evaluating the acoustic quality from the measurements (the simulations) consists of convolving anechoic music with the measured (or simulated) impulse responses. In this way, a psycho-acoustic test is achieved using a virtual sound field representation. The listening room ‘Arlecchino’ at the University of Bologna includes ambisonics (up to fifth order) and stereo-dipole playback for virtual reproduction of sound in rooms. In this article, the effectiveness of the listening room ‘Arlecchino’ is first analysed, comparing acoustic parameters obtained from binaural impulse responses measured in some opera houses (in Italy) and auditorium (in Japan) with those virtually measured after the virtual reconstruction obtained in the listening rooms. The similarity between real and virtual sound fields, has been evaluated by comparing different acoustic parameters calculated by real and virtual sound fields, in four halls in different configurations, by means of the stereo-dipole method. In the second part of the article, the listening room was used to analyse the variation in interaural cross-correlation measurements in rooms obtained considering different anechoic sound signals convolved with the binaural impulse responses, to quantify the variation of the interaural cross correlation with different motifs. For this purpose, two different musical instrument digital interface musical motifs, very different from each other for their music characteristics, have been considered. Moreover, for each musical motif, different sound characteristics (i.e. different musical instruments) were considered, to consider both the rhythmic and timbre aspect. Citation: Building Acoustics PubDate: 2020-06-05T10:49:00Z DOI: 10.1177/1351010X20926791
Authors:Lamberto Tronchin, Francesca Merli, Massimiliano Manfren, Benedetto Nastasi First page: 333 Abstract: Building Acoustics, Ahead of Print. Soundfield diffuseness in rooms is considered a fundamental aspect of a high-quality room acoustics. Since early studies by Hodgson up to more recent studies of Shtrepi and Embrechts, it was shown that high levels of sound diffuseness could guarantee blending of music, as well as spatial sound perception by listeners, and this could enhance the global indoor acoustic quality. Conversely, Italian-style Opera houses represent an important architectural place, in which the special features of the rich decorations, and the specific characteristics of the volume, give a unique atmosphere, including a peculiar psycho-acoustics impression. However, some geometric properties of the opera houses could influence the global acoustic perception. The shape of the marmorino wall on the stalls, as well as the parallelism of the lateral walls in the boxes, often causes a lack of spaciousness and sometimes in the worst cases provokes focalization. This phenomenon leads to design special devices that could be inserted in the theatres, to avoid focalization, even if they are rarely accepted. This article deals with the design of some acoustic diffusing panels and their functioning in three different theatres, combining both acoustics needs with architectural constraints. The article starts analysing and commenting on the issues that resulted from the measurements conducted in an Italian opera house. In the following step, three examples of the design of diffusing panels are proposed. Finally, the results of diffusion and scattering coefficient of panels realized in the last theatre considered here are reported. Citation: Building Acoustics PubDate: 2020-06-08T05:07:03Z DOI: 10.1177/1351010X20929216
Authors:Arkadiusz Pawlik, Stanislaw Frackowiak, Karol Leluk First page: 357 Abstract: Building Acoustics, Ahead of Print. In this work, a number of tests were carried out to evaluate the effectiveness of the vibro-acoustic behavior composite consisting of a biodegradable polymer matrix (polylactid acid) and a filler in the form of natural flax fibers, with a moisture content of 2.03% after drying in 80°C for 4 h. To improve material dampening properties, polylactid acid was plasticized with polyethylene glycol 400 and triethyl citrate. The flax fiber content of the composite was 10, 20, and 30 wt%. Mechanical properties at bending and tensile were performed. For the measurement of vibro-acoustic suppression effectiveness, composite samples have been made to enable installation in the measurement system. The measuring system consisted of an unbalanced axial electric motor, resting on a steel frame placed on vibration suppressor. For comparison, the commercial grade vibration suppressor was used. In order to evaluate the vibration damping of the system by vibration suppressor, vibration engine frame vibration was forced by acceleration of the engine’s rotational speed to specific frequencies. It has been proven that the type of the plasticizer used in the composite changes the vibro-acoustic suppression parameter. Also, the length and the weight percentage of the fibers result in lower material damping values. Citation: Building Acoustics PubDate: 2020-04-27T02:59:33Z DOI: 10.1177/1351010X20912938
Authors:Joan Lluis Zamora Mestre, Andrea Niampira First page: 367 Abstract: Building Acoustics, Ahead of Print. The use of double-sheet enclosures with an intermediate non-ventilated air cavity guarantees a higher airborne sound insulation. The insulation advantages depend on air tightness and the placement of sound absorbing material in the air cavity. The lightweight ventilated façade is a system constructed by the addition of an external light cladding on a heavy single wall to establish an intermediate air cavity. This air cavity can be ventilated under controlled cooling effects, because of Sun’s radiation, and to reduce the risk of dampness caused by rainwater. Owing to this ventilation, acoustic insulation of the lightweight ventilated façade could be less effective. However, some authors indicate that air cavity moderate ventilation does not necessarily lead to a significant reduction in the airborne sound insulation. The authors previously verified this situation in a real building where the existing façade of masonry walls was transformed into a lightweight ventilated façade. The preliminary results indicate the acoustic benefits can be compatible with the hygrothermal benefits derived from controlled ventilation. This article presents the next step, the evaluation of the lightweight ventilated façade acoustic performance under laboratory conditions to revalidate the previous results and refining aspects as the air cavity thickness or the state of openings ventilation. The main results obtained indicate that the airborne sound insulation in laboratory is aligned with the previous results in a real building. Air cavity thickness from 110 to 175 mm and ventilation openings from 0% to 3.84% of the façade area does not lead to a significant reduction in the airborne sound insulation. Citation: Building Acoustics PubDate: 2020-05-11T09:19:20Z DOI: 10.1177/1351010X20916719
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