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13.13 The Future of Building Acoustics Measurement & Modeling

Measuring the force due to standard tapping machine and floor impedance for ASTM standards
Time: 12:20 pm

Author: Sunit Girdhar

Abstract ID: 1644

The standard tapping machine used for the ASTM and ISO tests does not require the test engineer to measure the input force in the system, instead, just relies on measuring the sound pressure level (SPL) output. However, the input force depends on the assembly itself being tested. The input force levels are lower for lightweight assemblies like hardwood floors as compared to heavyweight assemblies like concrete. Without knowledge of this input force, the output SPL levels cannot and should not be compared using the IIC (Impact Insulation Class) rating. In this work, we measured the input force levels for the same tapping machine on different floors. We also measured the floor impedance for different assemblies and their comparison is also shown. This work shows the importance of measuring input forces for the standard floor-ceiling assembly impact tests

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Measurement survey using acoustic measurement network and sound environment evaluation system by experience sampling
Time: 2:00 pm

Author: Kengo Togashi

Abstract ID: 2952

The use of open-plan offices is increasing as they are effective in improving intellectual productivity by fostering a communication among workers. Previous research on the relationship between the indoor sound environment and intellectual productivity has mostly reported the impact of the sound environment on the tasks that individuals work on. However, there has been no research on the impact of sound environment on office spaces where multiple workers are actually working. In this study, we developed a system that can analyze the individual characteristics of workers in relation to the sound environment by simultaneously measuring their evaluation to the sound environment and the sound environment of the office. The system collected workers’ evaluation of their impressions to the sound environment through a regular questionnaire using the experience sampling method. At the same time, it measured the sound environment of the office with multiple small measurement devices. The obtained sound environment evaluation data and the acoustic data of the office were stored in a single database. Finally, this system was run in a working environment to evaluate the sound environment on a trial basis.

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Learning-based estimation of individual absorption profiles from a single room impulse response with known positions of source, sensor and surfaces
Time: 11:00 am

Author: Stéphane Dilungana

Abstract ID: 3186

In situ estimation of the individual absorption profiles of a room remains a challenging problem in building acoustics. This work is aimed at studying the feasibility of this estimation in a shoebox room of fixed and known geometry, using a room impulse response measured from a source and sensor at fixed and known positions. This problem is tackled using supervised learning. Three neural network architectures are compared. Simulated training and validation sets featuring various types of perturbations (surface diffusion, geometrical errors and additive white Gaussian noise) are generated. An extensive empirical simulated study is carried out to determine the influence of these perturbations on the performances of learned models, and to determine which components of the room impulse response are most useful for absorption coefficients prediction. Trained models are shown to yield errors significantly smaller than those of a naive mean estimator on every simulated datasets, including those featuring realistic perturbation levels. Our study outlines the benefit of using convolutional neural network layers, especially when geometrical errors exist. It also reveals that early acoustic echoes are the most salient feature of room impulse responses for absorption coefficient prediction under a fixed geometry.

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Acoustic design tools for estimation of sound insulation performance of wood wall and floor assemblies
Time: 5:00 pm

Author: Cheng Qian

Abstract ID: 1384

The National Building Code of Canada 2015 stipulates the minimum requirements of the airborne sound insulation transmission through common interior walls and ceiling/floor assemblies. The required minimum Apparent Sound Transmission Class (ASTC) is 47 in Canada, whereas the Impact Insulation Class (IIC) for floors is recommended to be higher than 55. For many years, significant efforts were made to develop sound insulation prediction models or tools to predict the sound insulation performance of wall and floor/ceiling assemblies at the design phase in order to meet the requirements and the recommendations made by codes. However, today few models can provide a reliable acoustics design tool. In this document, three prediction tools thought to be practically useful are presented and evaluated. Between these three prediction tools, one is an analytical model of the Insul software while the other two are empirical models developed by the National Research Council of Canada and the American Wood Council. This paper compared the STC and IIC ratings of wood wall and floor assemblies estimated by these three models and verified them by the measured STC and IIC ratings. This work aims at providing an idea for readers to choose a suitable design tool to proceed with their acoustic designs.

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An explicit time-domain FEM for acoustic simulation in rooms with frequency-dependent impedance boundary: Comparison of performance in 2D simulation with frequency-domain FEM
Time: 5:40 pm

Author: Takumi Yoshida

Abstract ID: 1757

Accurate boundary modelings that address the frequency-dependent sound absorption characteristics of various sound absorbers are crucial for wave-based room acoustic simulation. In time-domain simulations, however, a computationally demanding convolution appears in frequency-dependent impedance boundary conditions. The present paper proposes a room acoustic solver with a fourth-order accurate explicit TD-FEM, incorporating a frequency-dependent absorbing boundary condition efficiently using a recursive convolution method, namely the auxiliary differential equation (ADE) method. Its performance against the fourth-order accurate frequency-domain FEM is examined via 2D real-scale room acoustic problems, solving a sound propagation in an office room up to 4.5 kHz.  Firstly, we describe briefly the formulation of the proposed room acoustics solver based on the explicit TD-FEM. Then, the discretization error property of the proposed method is evaluated via an impedance tube problem, including a frequency-dependent impedance boundary of porous sound absorber. Finally, the accuracy and efficiency of the proposed method are demonstrated with the comparison of frequency-domain FEM solver, which uses a sparse direct solver for the solution of the linear system at each frequency. Results showed the proposed method can perform an acoustic simulation with significantly low computational costs compared to the frequency-domain solver while keeping an acceptable level of accuracy.

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Quantifying sound transmission of building structures for optimization in early-stage design
Time: 4:20 pm

Author: Jonathan Broyles

Abstract ID: 1781

Technological advancements in computational building modeling have enabled designers to conduct many simulations at both the building and component levels. With the evolution of parametric modeling at the early stage of building design, designers can evaluate multiple design options and identify the best performing solutions. However, to conduct design space exploration or optimization, an objective function is needed to evaluate a design’s performance. While defined objectives exist for building design considerations such as sustainability, energy usage, and structural performance there is not a single, encompassing objective that can accurately assess acoustic performance for optimization. This paper proposes the development of a novel acoustic objective function that encompasses sound transmission when designing floors, walls, or other acoustic barriers. The composite function will incorporate both air-borne and structure-borne sound simultaneously to determine the appropriate percentages for the formulation of the composite function. The results of the composite acoustic function for multiple floor constructions will be compared for the determination of a final acoustic transmission composite function. This study will detail why the implementation of a composite acoustic function is valuable for design optimization for sound transmission, what the limitations of this method are, and future applications of a composite acoustic function.

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Analytical model of the diffuse sound transmission loss of finite double panel structures
Time: 4:40 pm

Author: Javier Vazquez Torre

Abstract ID: 1908

An analytical model for the forced sound transmission loss of finite single-leaf walls using a variational technique was previously developed and validated. As the double panel is one of the most used structures in building acoustics, the aim of this paper is to extend the analytical model to consider double panel structures. Analytical formulas for the forced part of the airborne sound insulation of finite sized double panel structures are derived using a variational technique based on the integral-differential equation of the fluid loaded panels. The formulas are valid in the entire audible frequency range. The results are compared to alternative analytical models and measurements, with reasonable agreement.

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A Sound Insulation Prediction Model for Floor Structures in Wooden Buildings Using Neural Networks approach
Time: 5:20 pm

Author: Mohamad BADER EDDIN

Abstract ID: 2619

Recently, machine learning and its applications have gained a large attraction in different fields. Accurate predictions in building acoustics is vital especially in the design stage. This paper presents a sound insulation prediction model based on Artificial Neural Networks (ANNs) to estimate acoustic performance for airborne and impact sound insulation of floor structures. At an initial stage, the prediction model was developed and tested for a small amount of data, specifically 67 measurement curves in one third octave bands. The results indicate that the model can predict the weighted airborne sound insulation for various floors with an error around 1 dB, while the accuracy decreases for the impact sound especially for complex floor configurations due to large error deviations in high frequency bands between the real and estimated values. The model also shows a very good accuracy in predicting the airborne and impact sound insulation curves in the low frequencies, which are of higher interest usually in building acoustics. Keywords: building acoustics, airborne sound, impact sound, prediction model, neural networks

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Proacustica Handbook: noise and vibration control in building installations
Time: 11:00 am

Author: Jose Nepomuceno

Abstract ID: 2948

Proacústica is a nonprofit entity created in 2010 to congregate companies and professionals willing to leverage the development of acoustics in Brazil. Three technical committees (TCs): Environmental Acoustics, Building Acoustics, and Room Acoustics, contribute to the drafting of laws, standards, production of technical content, and integration between different players of the market. By 2021, the Room Acoustics TC incorporated three Working Groups: Special Rooms, Schools and Noise Control and Vibration Control – the last one dedicated to the Proacustica Handbook: Noise and Vibration Control In Building Installations. The purpose of this publication is to describe the step-by-step measures to implement noise and vibration control strategies in buildings. These strategies are aimed at the particularities of the Brazilian market at the moment and also a way to improve how M/E/P equipment manufacturers, installers, designers, and acoustic consultants approach the subject from the design to the construction, Important technical discussions among participants included: the use of sound pressure versus sound power data for equipment; the sound rating for diffusers, VAVs, and other ductwork devices; vibration isolation guidelines, among other topics. This paper presents the Handbook structure, relevant discussions, and recommendations to be published as a final document by the end of 2021.

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