Finite element sound field analysis on measurement of absorption coefficient in a reverberation room -Relationships between inclination of walls and measurement results-

The absorption coefficients in a reverberation room are most representative measure for evaluating absorption performance of architectural materials. However, it is well known that measurement results of the coefficient vary according to a room shape of the measurement and area of the specimen. Numerical analyses based on wave acoustics are effective tools to investigate these factors on absorption coefficient measurement in reverberation room. In this study, sound fields for the measurement of absorption coefficient in reverberation room are analyzed by time domain finite element method (TDFEM). This study shows effectiveness of the analysis for investigation on causes of variation in the measurement results and improvement methods of the measurement. First, some measurement sound fields for absorption coefficient in reverberation rooms the walls of which are incline or decline are analyzed by the TDFEM. Next, reverberation times in each sound fields are calculated from the results obtained by TDFEM and the absorption coefficients are evaluated from the reverberation time of the room with and without specimen. Finally, the relationships among room shape, degree of inclination of the wall, the sound absorption coefficient of the specimen, frequencies and the measurement absorption coefficient are investigated.

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APPLICATION OF KRYLOV SUBSPACE METHODS TO FINITE ELEMENT SOUND FIELD ANALYSIS : Numerical analysis of large-scale sound fields using iterative solvers Part II

Journal of Environmental Engineering (Transactions of AIJ) ◽

10.3130/aije.71.11 ◽

2006 ◽

Vol 71 (610) ◽

pp. 11-18

Author(s):

Noriko OKAMOTO ◽

Yosuke YASUDA ◽

Toru OTSURU ◽

Reiji TOMIKU

Keyword(s):

Finite Element ◽

Numerical Analysis ◽

Large Scale ◽

Krylov Subspace ◽

Sound Field ◽

Krylov Subspace Methods ◽

Iterative Solvers ◽

Field Analysis ◽

Subspace Methods ◽

Sound Fields

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Finite element sound field analysis for investigation on measurement mechanism of reverberation time in non-diffuse sound field

The Journal of the Acoustical Society of America ◽

10.1121/1.4970467 ◽

2016 ◽

Vol 140 (4) ◽

pp. 3292-3292

Author(s):

Reiji Tomiku ◽

Toru Otsuru ◽

Noriko Okamoto ◽

Takeshi Okuzono ◽

Youtarou Kimura

Keyword(s):

Finite Element ◽

Sound Field ◽

Field Analysis ◽

Reverberation Time ◽

Measurement Mechanism

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Quantifying Non-Linearity in Early Decay Curves of Measured and Computer-Modeled Room Impulse Responses of a Highly Non-Diffuse Room Exhibiting Flutter Echo

Volume 1: Acoustics, Vibration, and Phononics ◽

10.1115/imece2020-24348 ◽

2020 ◽

Author(s):

Heather L. Lai ◽

Brian Hamilton

Keyword(s):

Linear Regression ◽

Computer Modeling ◽

Impulse Response ◽

Decay Curve ◽

Sound Field ◽

Energy Decay ◽

Room Acoustics ◽

Reverberation Time ◽

Sound Fields ◽

Regression Curves

Abstract This paper investigates the use of two room acoustics metrics designed to evaluate the degree to which the linearity assumptions of the energy density curves are valid. The study focuses on measured and computer-modeled energy density curves derived from the room impulse response of a space exhibiting a highly non-diffuse sound field due to flutter echo. In conjunction with acoustical remediation, room impulse response measurements were taken before and after the installation of the acoustical panels. A very dramatic decrease in the reverberation time was experienced due to the addition of the acoustical panels. The two non-linearity metrics used in this study are the non-linearity parameter and the curvature. These metrics are calculated from the energy decay curves computed per octave band, based on the definitions presented in ISO 3382-2. The non-linearity parameter quantifies the deviation of the EDC from a straight line fit used to generated T20 and T30 reverberation times. Where the reverberation times are calculated based on a linear regression of the data relating to either −5 to −25 dB for T20 or −5 to −35 dB for T30 reverberation time calculations. This deviation is quantified using the correlation coefficient between the energy decay curve and the linear regression for the specified data. In order to graphically demonstrate these non-linearity metrics, the energy decay curves are plotted along with the linear regression curves for the T20 and T30 reverberation time for both the measured data and two different room acoustics computer-modeling techniques, geometric acoustics modeling and finite-difference wave-based modeling. The intent of plotting these curves together is to demonstrate the relationship between these metrics and the energy decay curve, and to evaluate their use for quantifying degree of non-linearity in non-diffuse sound fields. Observations of these graphical representations are used to evaluate the accuracy of reverberation time estimations in non-diffuse environments, and to evaluate the use of these non-linearity parameters for comparison of different computer-modeling techniques or room configurations. Using these techniques, the non-linearity parameter based on both T20 and T30 linear regression curves and the curvature parameter were calculated over 250–4000 Hz octave bands for the measured and computer-modeled room impulse response curves at two different locations and two different room configurations. Observations of these calculated results are used to evaluate the consistency of these metrics, and the application of these metrics to quantifying the degree of non-linearity of the energy decay curve derived from a non-diffuse sound field. These calculated values are also used to evaluate the differences in the degree of diffusivity between the measured and computer-modeled room impulse response. Acoustical computer modeling is often based on geometrical acoustics using ray-tracing and image-source algorithms, however, in non-diffuse sound fields, wave based methods are often able to better model the characteristic sound wave patterns that are developed. It is of interest to study whether these improvements in the wave based computer-modeling are also reflected in the non-linearity parameter calculations. The results showed that these metrics provide an effective criteria for identifying non-linearity in the energy decay curve, however for highly non-diffuse sound fields, the resulting values were found to be very sensitive to fluctuations in the energy decay curves and therefore, contain inconsistencies due to these differences.

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Optimization and Validation of Sound Absorption Performance of 10-Layer Gradient Compressed Porous Metal

Metals ◽

10.3390/met9050588 ◽

2019 ◽

Vol 9 (5) ◽

pp. 588 ◽

Cited By ~ 9

Author(s):

Fei Yang ◽

Xinmin Shen ◽

Panfeng Bai ◽

Xiaonan Zhang ◽

Zhizhong Li ◽

...

Keyword(s):

Finite Element ◽

Finite Element Simulation ◽

Sound Absorption ◽

Search Algorithm ◽

Theoretical Data ◽

Porous Metal ◽

Cuckoo Search ◽

Absorption Coefficients ◽

Element Simulation ◽

Absorption Performance

Sound absorption performance of a porous metal can be improved by compression and optimal permutation, which is favorable to promote its application in noise reduction. The 10-layer gradient compressed porous metal was proposed to obtain optimal sound absorption performance. A theoretical model of the sound absorption coefficient of the multilayer gradient compressed porous metal was constructed according to the Johnson-Champoux-Allard model. Optimal parameters for the best sound absorption performance of the 10-layer gradient compressed porous metal were achieved by a cuckoo search algorithm with the varied constraint conditions. Preliminary verification of the optimal sound absorber was conducted by the finite element simulation, and further experimental validation was obtained through the standing wave tube measurement. Consistencies among the theoretical data, the simulation data, and the experimental data proved accuracies of the theoretical sound absorption model, the cuckoo search optimization algorithm, and the finite element simulation method. For the investigated frequency ranges of 100–1000 Hz, 100–2000 Hz, 100–4000 Hz, and 100–6000 Hz, actual average sound absorption coefficients of optimal 10-layer gradient compressed porous metal were 0.3325, 0.5412, 0.7461, and 0.7617, respectively, which exhibited the larger sound absorption coefficients relative to those of the original porous metals and uniform 10-layer compressed porous metal with the same thickness of 20 mm.

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A Revised Sound Energy Theory Based on a New Formula for the Reverberation Radius in Rooms with Non-Diffuse Sound Field

Archives of Acoustics ◽

10.1515/aoa-2015-0005 ◽

2015 ◽

Vol 40 (1) ◽

pp. 33-40 ◽

Cited By ~ 2

Author(s):

Higini Arau-Puchades ◽

Umberto Berardi

Keyword(s):

Sound Absorption ◽

Sound Field ◽

Critical Distance ◽

Sound Level ◽

Reverberation Time ◽

Sound Energy ◽

Sound Fields ◽

Energy Theory ◽

New Interpretation ◽

New Formula

Abstract This paper discusses the concept of the reverberation radius, also known as critical distance, in rooms with non-uniformly distributed sound absorption. The reverberation radius is the distance from a sound source at which the direct sound level equals the reflected sound level. The currently used formulas to calculate the reverberation radius have been derived by the classic theories of Sabine or Eyring. However, these theories are only valid in perfectly diffused sound fields; thus, only when the energy density is constant throughout a room. Nevertheless, the generally used formulas for the reverberation radius have been used in any circumstance. Starting from theories for determining the reverberation time in non- diffuse sound fields, this paper firstly proposes a new formula to calculate the reverberation radius in rooms with non-uniformly distributed sound absorption. Then, a comparison between the classic formulas and the new one is performed in some rectangular rooms with non-uniformly distributed sound absorption. Finally, this paper introduces a new interpretation of the reverberation radius in non-diffuse sound fields. According to this interpretation, the time corresponding to the sound to travel a reverberation radius should be assumed as the lower limit of integration of the diffuse sound energy

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The influence of the distribution of sound absorbing materials on the estimation of reverberation time in rooms

E3S Web of Conferences ◽

10.1051/e3sconf/20184900078 ◽

2018 ◽

Vol 49 ◽

pp. 00078

Author(s):

Marcelina Olechowska ◽

Artur Nowoświat ◽

Jan Ślusarek ◽

Mateusz Latawiec

Keyword(s):

Absorption Coefficient ◽

Acoustic Field ◽

Sound Absorption ◽

Sound Field ◽

Reverberation Time ◽

Type D ◽

Absorbing Materials ◽

Absorbing Material ◽

Different Dimensions ◽

Materials Used

Reverberation time in rooms depends on many factors, e.g. cubature, surface of envelopes, sound absorption coefficient of materials used for the construction of the envelopes, geometry of rooms or the distribution of sound absorbing materials. The arrangement of sound absorbing materials in rooms has an impact on the dispersion of acoustic field, yet theoretical calculation models do not take into account this impact. According to these models, regardless of the arrangement of sound absorbing materials, the reverberation time in a room will remain unchanged. The present paper investigates the above problem by means of computer simulations. For the needs of the simulation, three rooms with different dimensions were adopted, i.e. type 'p' - a cuboidal room with a square base, type 'd' - a cuboidal room (with one side of the 'p' room lengthened), type 'w' - a cuboidal room (with the height of the room lengthened 'p'). During the simulation, the way of acoustic field dispersion was being changed and its influence on the reverberation time in the rooms was being determined. The authors investigated two situations. The first one involved a non-dampened room, in which the sound absorbing material was being arranged differently. The second one involved a welldampened room, and the dispersion of sound field was analyzed depending on the location of the reflecting material.

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Diffusion Equation-Based Finite Element Modeling of a Monumental Worship Space

Journal of Computational Acoustics ◽

10.1142/s0218396x17500291 ◽

2017 ◽

Vol 25 (04) ◽

pp. 1750029 ◽

Cited By ~ 1

Author(s):

Zühre Sü Gül ◽

Ning Xiang ◽

Mehmet Çalışkan

Keyword(s):

Finite Element ◽

Diffusion Equation ◽

Geometric Model ◽

Three Dimensional ◽

Sound Field ◽

Equation Model ◽

Field Analysis ◽

Room Acoustics ◽

Sound Energy ◽

Worship Space

In this work, a diffusion equation model (DEM) is applied to a room acoustics case for in-depth sound field analysis. Background of the theory, the governing and boundary equations specifically applicable to this study are presented. A three-dimensional geometric model of a monumental worship space is composed. The DEM is solved over this model in a finite element framework to obtain sound energy densities. The sound field within the monument is numerically assessed; spatial sound energy distributions and flow vector analysis are conducted through the time-dependent DEM solutions.

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A TECHNIQUE FOR PLANE-SYMMETRIC SOUND FIELD ANALYSIS IN THE FAST MULTIPOLE BOUNDARY ELEMENT METHOD

Journal of Computational Acoustics ◽

10.1142/s0218396x05002591 ◽

2005 ◽

Vol 13 (01) ◽

pp. 71-85 ◽

Cited By ~ 23

Author(s):

Y. YASUDA ◽

T. SAKUMA

Keyword(s):

Boundary Element Method ◽

Boundary Element ◽

Large Scale ◽

Numerical Study ◽

Sound Field ◽

Field Analysis ◽

Fast Multipole ◽

Plane Symmetric ◽

Sound Fields ◽

Element Method

The fast multipole boundary element method (FMBEM) is an advanced BEM, with which both the operation count and the memory requirements are O(Na log b N) for large-scale problems, where N is the degree of freedom (DOF), a ≥ 1 and b ≥ 0. In this paper, an efficient technique for analyses of plane-symmetric sound fields in the acoustic FMBEM is proposed. Half-space sound fields where an infinite rigid plane exists are typical cases of these fields. When one plane of symmetry is assumed, the number of elements and cells required for the FMBEM with this technique are half of those for the FMBEM used in a naive manner. In consequence, this technique reduces both the computational complexity and the memory requirements for the FMBEM almost by half. The technique is validated with respect to accuracy and efficiency through numerical study.

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