Numerical evidence of mixing in rooms using the free path temporal distribution

Billon, Alexis; Embrechts, Jean-Jacques

doi:10.1121/1.3623747

Cited by 6 publications

(4 citation statements)

References 27 publications

(49 reference statements)

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“…Several studies [8,16,20,21] have shown that the sound energy density in ar everberation experiment follows an exponential decay (t>0) in rooms with diffusely reflecting walls. Moreover, the slope of the decay is approximately the same at different positions in the room, though sometimes significantly different from the one predicted by Sabine or Eyring formula [20, p.139].…”

Section: Rooms With Diffusely Reflecting Boundaries and Diffuse Soundmentioning

confidence: 99%

A Geometrical Acoustics Approach Linking Surface Scattering and Reverberation in Room Acoustics

Embrechts¹

2014

Acta Acustica united with Acustica

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Ageneral model of the influence of surface scattering on the reverberation time would have several applications in room acoustics. Such amodel is not yet available, and it is the purpose of this paper to investigate ageometrical acoustics approach. Starting from the radiative transfer equation, an exponential solution is first developed for the reverberation energy decay in rooms with diffusely reflecting boundaries. Differences with the diffuse sound field (Sabine)t heory are highlighted, leading to am odified formula for the reverberation time which is shown to be more in accordance with ray tracing simulations. Ag eneral model is then proposed for rooms in which specular and diffuse reflections coexist. This general model is applied in rooms where the specular contribution can be assumed to be quasi-isotropic and uniform. Under this assumption, the reverberation decay is represented by the sum of twoexponential functions, depending on the scattering coefficients. However, it is shown that the influence of surfaces' scattering on reverberation is rather limited in this case. On the contrary,r ooms with a pair of parallel surfaces are prone to create significant anisotropyi nt he cloud of image sources. An analytical formulation is proposed in this case for the specular and diffuse contributions, provided that some assumptions are again made on the specularly reflected sound field. The final expression is not really intuitive concerning the relation between scattering coefficients and reverberation, butitcontains all the variables influencing this relation. This allows fast evaluations of the effect of surface scattering in particular situations. Finally,the application of this model to room acoustics computer simulations is illustrated by an example. PACS no. 43.55.Br,43.55.Ka 864

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Section: Rooms With Diffusely Reflecting Boundaries and Diffuse Soundmentioning

confidence: 99%

A Geometrical Acoustics Approach Linking Surface Scattering and Reverberation in Room Acoustics

Embrechts¹

2014

Acta Acustica united with Acustica

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“…The results from the initial ray tracing procedure (1) are then employed to determine the diffused energy (4) and the remaining sound energy in the cavity at the transition time (5). Diffused sound energy is redirected into time bins that correspond to specific time windows before the transition time.…”

Section: Processmentioning

confidence: 99%

“…The impulse response can be obtained via testing or using predictions from numerical models. Such models are typically based on ray or beam tracing for the direct field and early reflections, and on statistical models for the late reflections which arrive after the so called transition time 5 .…”

Section: Introductionmentioning

confidence: 99%

Predicting speech transmissibility using ray tracing and statistical energy analysis

Merz

Cotoni

Shorter

2013

The Journal of the Acoustical Society of America

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Statistical Energy Analysis (SEA) is used across many different industries to predict interior noise, for example the background noise in vehicle interiors due to steady-state exterior sources. SEA describes the reverberant response, however some applications exist where the direct field from interior sources is also important. This includes prediction of audio system sound quality in automobiles, or speech intelligibility for public address systems in trains, coaches, and aircrafts. Computing these indices requires both the background noise level and the impulse response at the listener location due a source representing a loudspeaker. Geometrical methods such as ray tracing are often used for describing the early impulse response where only few reflections of the direct field are involved; however they are not well suited for describing the late impulse response due to the increasing number of reflections. Instead a statistical description similar to transient SEA is typically used for the late time reflections. An SEA model of background noise therefore contains most of the information needed for predicting speech transmissibility: the background noise prediction, a simplified geometry of the acoustic space, and accurate wall impedance models. This paper demonstrates prediction of speech transmissibility by using ray tracing with typical SEA models.

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“…The diffusion model assumes that the energy is sufficiently scattered. In mixing rooms, the sound field becomes diffuse after about three mean-free time (a mean-free time is equal to λ/c, the time needed to travel a mean-free path) [30]. So the sound field ought to be sufficiently scattered at shorter times for diffusion model to be valid.…”

Section: Room Acoustics Criteriamentioning

confidence: 99%

Acoustic Predictions in Industrial Spaces Using a Diffusion Model

Billon

Picaut²,

Valeau

et al. 2012

Advances in Acoustics and Vibration

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Industrial spaces are known to be very noisy working environment. This noise exposure can be uncomfortable, tiring, or even harmful, at worst. Industrial spaces have several characteristics: they are often huge flat volumes fitted with many obstacles and sound sources. Moreover, they are usually surrounded by rooms where low noise levels are required. The existing prediction tools can seldom model all these phenomena accurately. In this paper, a prediction model based on a diffusion equation is presented. The successive developments carried out to deal with the various propagating phenomena met in industrial spaces are shown. For each phenomenon, numerical or experimental examples are given to highlight the validity of this model. It is also shown that its computation load is very little in comparison to ray-tracing-based methods. In addition, this model can be used as a reliable and flexible tool to study the physics of the coupling between rooms. Finally, an application to a virtual factory is presented.

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Numerical evidence of mixing in rooms using the free path temporal distribution

Cited by 6 publications

References 27 publications

A Geometrical Acoustics Approach Linking Surface Scattering and Reverberation in Room Acoustics

A Geometrical Acoustics Approach Linking Surface Scattering and Reverberation in Room Acoustics

Predicting speech transmissibility using ray tracing and statistical energy analysis

Acoustic Predictions in Industrial Spaces Using a Diffusion Model

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