Theoretical Determination of the Random-Incidence Scattering Coefficients of Infinite Rigid Surfaces with a Periodic Rectangular Roughness Profile

Embrechts, Jean-Jacques; Billon, Alexis

doi:10.3813/aaa.918441

Cited by 11 publications

(13 citation statements)

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“…This coefficient can be measured under free field or random incidence in the laboratory [3,4,5]. It can also be computed for some typical, periodic or random roughness profiles [6,7].…”

Section: Introductionmentioning

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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“…This coefficient can be measured under free field or random incidence in the laboratory [3,4,5]. It can also be computed for some typical, periodic or random roughness profiles [6,7].…”

Section: Introductionmentioning

confidence: 99%

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

Embrechts¹

2014

Acta Acustica united with Acustica

Self Cite

View full text Add to dashboard Cite

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“…It should be noted that there are large structures in the actual building façade, i.e., sizable rectangles on Street 3-FA. When the dimensions of the plane surface are significantly larger than the wavelength, it functions similarly to a specular reflector rather than a diffuser [43]. Therefore, rectangular structures with large plane surfaces (the ratio of the dimension of the surface to the wavelength was larger than 10, 6.8 m for 500 Hz) were considered as planes rather than diffusers when counting the coverage density.…”

Section: Estimation Of Acoustic Parameters Of Building Façadesmentioning

confidence: 99%

A Hybrid Model for Investigating the Effect of Scattering from Building Façade on Sound Propagation in Street Canyons

Kang

2019

Applied Sciences

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Street canyons are basic components of modern cities. Sound propagation in streets has been proven to be significantly affected by reflections from building façades. In this paper, an iterative model combining acoustic radiosity and the image source method (IMCRI) is proposed to investigate the effect of diffuse reflections on sound propagation in urban street canyons. By applying image patches, this model calculates both specular reflected components and diffuse reflected components in every reflection. The accuracy of this model is then validated with full-scale measured data from five actual streets with different scattering conditions. Good agreements of sound pressure level and reverberation time are found between the IMCRI and the measurements. The performance of the IMCRI is found to be superior to those of the existing energy models, especially for the reverberation time simulation.

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“…Figure 12 shows normal-incidence scattering coefficients of Sample R1 in the two orientations, determined from the measured reverberation times for various decay ranges. The grey solid and dotted lines represent theoretical results for the infinite sample [16], and numerical results for the sample 3 m square (750 mm square in 1/4 scale) [17], respectively. Although the measured results are obviously unreliable below 500 Hz, good agreement is generally seen between the measured and numerical results.…”

Section: Measurement Proceduresmentioning

confidence: 99%

“…In order to establish the proposed method, 1/4-scale experiments are performed to examine the two points: the measurement procedure for energy decay evaluation to determine onedimensional reverberation times, and the test arrangement, such as the dimensions of the room and the size and orientation of the sample. Furthermore, the validity of the measurement method is discussed in comparison with theoretical results for infinite surfaces [16], and numerical results for finite samples in the free field [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

A laboratory method for measuring normal-incidence scattering coefficients of architectural surfaces

Sakuma

Lee

Inoue

2016

Acoust. Sci. & Tech.

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Regarding scattering coefficient that represents acoustic scattering capability of architectural surfaces, a reverberation room method for measuring random-incidence values has been standardized in ISO 17497-1, whereas any method has not yet fully established for incidence-angledependent values. In this paper, a laboratory measurement method is proposed for normal-incidence scattering coefficients, which will be useful for room acoustics design, particularly assessment of flutter echoes. The measurement is performed in a rectangular room where highly absorbent materials are installed on all sidewalls, and a test sample is mounted on the entire floor. In the quasi-onedimensional sound field between the floor and ceiling, normal-incidence scattering coefficients of the sample are estimated by measuring the changes of reverberation times with and without the sample. In order to establish the proposed method, the measurement procedure and the test arrangement are examined in 1/4-scale experiments, and finally, it is validated in comparison with theoretical and numerical results.

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Theoretical Determination of the Random-Incidence Scattering Coefficients of Infinite Rigid Surfaces with a Periodic Rectangular Roughness Profile

Cited by 11 publications

References 0 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

A Hybrid Model for Investigating the Effect of Scattering from Building Façade on Sound Propagation in Street Canyons

A laboratory method for measuring normal-incidence scattering coefficients of architectural surfaces

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