Cubic room with diffuse reflection and uniform absorption

Description

Academic case: Cubic room (10m x 10m x 10m) with 100% diffuse reflection and 20% uniform surface absorption, with a single source at (3,3,3) and 3 lines of 9 punctual receivers along the 3 diagionals of the room.

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

What is tested?

Comparison between SPPS and data from the radiosity method, as described in [Kang, 2002]. This allows to validate the diffuse reflection in SPPS.

[Kang, 2002] KANG, Jian. Acoustics of Long Spaces: theory and design guidance. Thomas Telford, 2002. www.thomastelford.com/books/bookshop_main.asp;

CAUTION - The following results present comparisons between numerical simulations carried out with I-Simpa and 'reference' data available in the scientific literature. However, 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.). In addition, some numerical models (like SPPS), based on random methods, may produce small deviations between two distinct simulations.

Results

Early decay time (EDT) along line 1

This comparison between the EDT calculated with the SPPS code and those from the reference method (i.e. the radiosity method) shows a good agreement, with a minor deviation aroound source.und the location of the s

Early decay time (EDT) along line 2

Regarding the y-scale, a very good agreement is observed between in terms of EDT, between the SPPS code and the reference method (i.e. the radiosity method).

Early decay time (EDT) along line 3

This figure shows an Inverted behavior that is difficult to explain, i.e. a decrease of the RT30 for the reference data, while we observe an increase of the RT30 with SPPS. It seems that the line 3 of the receivers is reversed between the SPPS simulation and the reference data. In this case, if we reversed the line, we observe a perfect agreement.

In addition, it must be note a difference for the receiver 9 between the two SPPS simulation, which is due a wrong position of this receiver in the old simulation.

Calculation parameters

ParametersValue
Active calculation of Atmospheric absorptionNO
Active calculation of diffusion by fitting objectsNO
Active calculation of direct field onlyNO
Active calculation of transmissionNO
Calculation methodEnergetic
Limit value of the particle extinction5.0
Number of sound particles per source1 000 000
Number of sound particles per source (display)0
Random initialization number0
Receiver radius0.31
Simulation length (s)2.000
Time step (s)0.002