Low room with perfectly reflection and total ground absorption

Description

Academic case: Low room (30m x 20m x 10m) with perfeclty diffuse and reflecting surfaces, except the ground with a total absorption, with a single source and 1 punctual receiver.

All elements of this simulation are licensed under Licence Creative Commons Attribution 4.0 International License.

What is tested?

Comparison between SPPS and the results obtained using a hybrid method (image-sources and radiosity) as described in [Korany, 2001], for a room with total ground absorption.

[Korany, 2001] N. Korany, J. Blauert, O. Abdel Alim, Acoustic simulation of rooms with boundaries of partially specular reflectivity, Applied Acoustics, Volume 62, Issue 7, July 2001, Pages 875-887, ISSN 0003-682X, dx.doi.org/10.1016/S0003-682X(00)00075-X.

CAUTION - The following results present comparisons between numerical simulations carried out with I-Simpa and 'reference' data available in the scientific literature.

  • It is difficult to prejudge the concept of 'reference'. The deviation between the simulations and the reference data that can be observed do not necessarily call into question the corresponding simulations but can also be associated with other sources of deviation (modeling assumptions, numerical instabilities, experimental uncertainties, etc.).
  • Note also that these comparaisons can also show the limitations of some numerical codes.

Results

Reverberation time (RT30)

The SPPS code gives a similar value of the reverberation time (RT30) than the hybrid method, while, as expected, the Sabine and Eyring formulae gives strong values for this specific room with a total absorption on the ground.

Calculation parameters

Parameters Value
Time step (s) 0.002
Active calculation of Atmospheric absorption NO
Active calculation of diffusion by fitting objects NO
Active calculation of direct field only NO
Active calculation of transmission NO
Calculation method Energetic
Limit value of the particle extinction 5.0
Number of sound particles per source 100 000 000
Number of sound particles per source (display) 0
Random initialization number 0
Receiver radius 0.31
Simulation length (s) 1.500