Influence of wall absorption on low-frequency dependence of reverberation time in room of irregular shape

Meissner, Mirosław

doi:10.1016/j.apacoust.2007.02.004

Cited by 31 publications

(19 citation statements)

References 13 publications

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“…However, in the low-frequency limit typical materials covering room walls are characterized by a low absorption: ℜe(Z)/ρc ≫ 1, thus it is possible to assume that the shapes of modes are well approximated by the uncoupled eigenfunctions Φ n determined for hard room walls (Dowell et al, 1977). Taking all this into account and assuming that a source term in the wave equation has the form −q(r) cos(ωt), where q(r) and ω are the volume source distribution and the source frequency, the sound pressure in a steady-state can be determined by (Meissner, 2008a) …”

Section: Room Acoustics In Low-frequency Rangementioning

confidence: 99%

Examination of the Effect of a Sound Source Location on the Steady-State Response of a Two-Room Coupled System

Meissner¹

2011

Archives of Acoustics

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In this paper, the computer modelling application based on the modal expansion method is developed to study the influence of a sound source location on a steadystate response of coupled rooms. In the research, an eigenvalue problem is solved numerically for a room system consisting of two rectangular spaces connected to one another. A numerical procedure enables the computation of shape and frequency of eigenmodes, and allows one to predict the potential and kinetic energy densities in a steady-state. In the first stage, a frequency room response for several source positions is investigated, demonstrating large deformations of this response for strong and weak modal excitations. Next, a particular attention is given to studying how the changes in a source position influence the room response when a source frequency is tuned to a resonant frequency of a strongly localized mode.

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Section: Room Acoustics In Low-frequency Rangementioning

confidence: 99%

Examination of the Effect of a Sound Source Location on the Steady-State Response of a Two-Room Coupled System

Meissner¹

2011

Archives of Acoustics

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“…In low-frequency range, the reverberant behaviour of room is strongly frequency dependent (Meissner, 2007b(Meissner, , 2008b. Thus, in a theoretical model it was assumed that a room is excited by a a pure-tone sound source.…”

Section: Simulation Of Reverberant Response Of Roommentioning

confidence: 99%

“…When a steady-state is achieved, the source is abruptly switched off and the sound energy accumulated inside the room interior is absorbed on walls and an acoustic reverberation takes place. This reverberation consists of carrier waveforms of the decaying envelope that can be described by exponentially decreasing cosinusoidal functions (Meissner, 2008b)…”

Section: Simulation Of Reverberant Response Of Roommentioning

confidence: 99%

Evaluation of Decay Times from Noisy Room Responses with Pure-Tone Excitation

Meissner¹

2013

Archives of Acoustics

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Reverberant responses are widely used to characterize acoustic properties of rooms, such as the early decay time (EDT) and the reverberation times T20 and T30. However, in real conditions a sound decay is often deformed by background noise, thus a precise evaluation of decay times from noisy room responses is the main problem. In this paper this issue is examined by means of numerical method where the decay times are estimated from the decay function that has been determined by nonlinear polynomial regression from a pressure envelope obtained via the discrete Hilbert transform. In numerical experiment the room responses were obtained from simulations of a sound decay for two-room coupled system. Calculation results have shown that background noise slightly affects the evaluation of reverberation times T20 and T30 as long as the signal-to-noise ratio (SNR) is not smaller than about 25 and 35 dB, respectively. However, when the SNR is close to about 20 and 30 dB, high overestimation of these times may occur as a result of bending up of the decay curve during the late decay.

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“…In this case the function describing time behaviour of the first mode (m, n = 0), the so-called Helmholtz mode that has an eigenfrequency equal to zero, is described by [24] P 00 (t) = Q 00 exp(−2r 00 t) ω 2 + 4r 2 00…”

Section: Theorymentioning

confidence: 99%

Computational studies of steady-state sound field and reverberant sound decay in a system of two coupled rooms

Meissner

2007

Open Physics

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Abstract:The acoustical properties of an irregularly shaped room consisting of two connected rectangular subrooms were studied. An eigenmode method supported by a numerical implementation has been used to predict acoustic characteristics of the coupled system, such as the distribution of the sound pressure in steady-state and the reverberation time. In the theoretical model a low-frequency limit was considered. In this case the eigenmodes are lightly damped, thus they were approximated by normal acoustic modes of a hard-walled room. The eigenfunctions and eigenfrequencies were computed numerically via application of a forced oscillator method with a finite difference algorithm. The influence of coupling between subrooms on acoustic parameters of the enclosure was demonstrated in numerical simulations where different distributions of absorbing materials on the walls of the subrooms and various positions of the sound source were assumed. Calculation results have shown that for large differences in the absorption coefficient in the subrooms the effect of modal localization contributes to peaks of RMS pressure in steady-state and a large increase in the reverberation time.

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Influence of wall absorption on low-frequency dependence of reverberation time in room of irregular shape

Cited by 31 publications

References 13 publications

Examination of the Effect of a Sound Source Location on the Steady-State Response of a Two-Room Coupled System

Examination of the Effect of a Sound Source Location on the Steady-State Response of a Two-Room Coupled System

Evaluation of Decay Times from Noisy Room Responses with Pure-Tone Excitation

Computational studies of steady-state sound field and reverberant sound decay in a system of two coupled rooms

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