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

Embrechts, Jean-Jacques

doi:10.3813/aaa.918766

Cited by 8 publications

(9 citation statements)

References 14 publications

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“…In section 'Inhomogeneity and sound diffusion in opera houses', we have reported the acoustic analysis in the Teatro Comunale in Bologna, which is considered one of the most relevant Italian-style opera houses in Italy, in which focalization could be found in some positions. We could extend this result stating that in Italian-style opera houses, there are very often problems of focalization of the sound field especially in the stalls and in the boxes (mainly in the first order) Moreover, several authors found that diffusion and scattering in Opera Houses represent a fundamental issue, [18][19][20] to be measured [21][22][23] or simulated. 24,25 This phenomenon leads to design special devices, as diffusing panels, that could be inserted in the theatres, to avoid focalization and improve the acoustic quality.…”

Section: The Acoustic Design Of Sound Diffusion In Three Italian Opersupporting

confidence: 63%

The sound diffusion in Italian Opera Houses: Some examples

et al. 2020

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Soundfield diffuseness in rooms is considered a fundamental aspect of a high-quality room acoustics. Since early studies by Hodgson up to more recent studies of Shtrepi and Embrechts, it was shown that high levels of sound diffuseness could guarantee blending of music, as well as spatial sound perception by listeners, and this could enhance the global indoor acoustic quality. Conversely, Italian-style Opera houses represent an important architectural place, in which the special features of the rich decorations, and the specific characteristics of the volume, give a unique atmosphere, including a peculiar psycho-acoustics impression. However, some geometric properties of the opera houses could influence the global acoustic perception. The shape of the marmorino wall on the stalls, as well as the parallelism of the lateral walls in the boxes, often causes a lack of spaciousness and sometimes in the worst cases provokes focalization. This phenomenon leads to design special devices that could be inserted in the theatres, to avoid focalization, even if they are rarely accepted. This article deals with the design of some acoustic diffusing panels and their functioning in three different theatres, combining both acoustics needs with architectural constraints. The article starts analysing and commenting on the issues that resulted from the measurements conducted in an Italian opera house. In the following step, three examples of the design of diffusing panels are proposed. Finally, the results of diffusion and scattering coefficient of panels realized in the last theatre considered here are reported.

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Section: The Acoustic Design Of Sound Diffusion In Three Italian Opersupporting

confidence: 63%

The sound diffusion in Italian Opera Houses: Some examples

et al. 2020

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“…However, the main problem is that for various enclosed spaces the Sabine-relation is not really adequate since the sound field is far from diffuse or the absorption is rather localized, for instance only the ceiling. To indicate at least possible deviations from the Sabine results an informative annex is included with a more detailed prediction model 15,16 . The effects are illustrated in figure 7, giving for a large room with absorbing ceiling and some scattering objects, the reverberation curve and time according to Sabine (S) and the estimation (3D) according to the annex of the standard.…”

Section: Reverberant Soundmentioning

confidence: 99%

The Development of the en 12354 Series 1989-2009

GERRETSEN

2023

8th European Conference on Noise Control 2009

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The development of the building acoustic prediction models in EN 12354 started twenty years ago, since the CPD made it necessary within Europe to link the acoustic performance of building products and elements to the performance of buildings. It concerned six acoustic aspects: airborne sound insulation, impact sound insulation, façade insulation, sound radiation to the outside, sound due to service equipment and reverberant sound in enclosed spaces. So these became the six parts of the standard, drafted by working group 2 of CEN Technical Committee 126 'Building Acoustics'. For various building elements the product quantities and their measurement methods were well established so these could be used as input to the prediction (estimation) of the building performance. But drafting these prediction models made clear what type of input data was still missing and what type of product quantities and measurement methods should be added. This generated activities in other working groups to define methods and in various countries to collect the product performances appropriate for the local building situations. An overview will be presented of these developments so far and the items still to be covered or improved.

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“…In this case, n is an integer number, p is an odd prime number and mod() is the operator modulus. By the input of these two variables, it is possible to determine the depth of the diffusing panel by the relationship of the maximum depth (d max ) and the maximum number of the sequence (n max ), as summarized in Equation (2).…”

Section: The Quadratic Residue Diffusers (Qrd)mentioning

confidence: 99%

“…The acoustic properties of surfaces are essential to estimate and calculate sound propagation within an enclosed space [1,2]. The acoustic scattering from surfaces and sound absorption characteristics are very important in all aspects of room acoustics, e.g., in opera houses, concert halls, industrial workplaces and reverberation chambers.…”

Section: Introductionmentioning

confidence: 99%

Comparison Failure and Successful Methodologies for Diffusion Measurements Undertaken inside Two Different Testing Rooms

et al. 2021

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The scattering phenomenon is known to be of great importance for the acoustic quality of a performance arts space. The scattering of sound can be achieved in different ways: it can be obtained by the presence of architectural and/or decorating elements inside a room (e.g., columns, statues), by the geometry and roughness of a surface (e.g., Quadratic Residue Diffuser (QRD)) and by the diffraction effect occurring when a sound wave hits the edges of an obstacle. This article deals with the surface scattering effects and the diffusion phenomenon only related to MDF and plywood panels tested by disposing the wells both horizontally and vertically. The test results undertaken inside a semi-reverberant room and inside a large reverberant room have been compared to highlight the success and the failure of the measuring methodologies. In detail, according to the existing standards and regulations (i.e., ISO 17497—Part 2), diffusion measurements have been undertaken on a few selected types of panel: two QRD panels (made of Medium Density Fiberboard (MDF) and plywood) with and without a smooth painted solid wood placed behind the QRD. The panels have been tested inside two rooms of different characteristics: a semi-anechoic chamber (Room A) and a large reverberant room (Room B). The volume size influenced the results that have been analyzed for both chambers, showing an overlap of reflections on panels tested inside Room A and a clear diffusion response for the panels tested inside Room B. In terms of the diffusion coefficient in all the octave bands between 125 Hz and 8 kHz, results should not be considered valid for panels tested in Room A because they were negatively impacted by extraneous reflections, while they are reliable for panels tested in Room B.

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

Cited by 8 publications

References 14 publications

The sound diffusion in Italian Opera Houses: Some examples

The sound diffusion in Italian Opera Houses: Some examples

The Development of the en 12354 Series 1989-2009

Comparison Failure and Successful Methodologies for Diffusion Measurements Undertaken inside Two Different Testing Rooms

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