Two coupled cubic rooms with or without a door in a separation wall

Description

Academic case: Comparison between SPPS and the classical theory of coupled rooms, for 2 cubic rooms (5m x 5m x 5m) [10% absorption, 100% diffusely reflecting] with or without a 1.8m² door (open, closed (no transmission) or R=10 dB) in a separation wall with an insertion loss R=10, 20, 30 dB

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 theoretical results from the classical theory of reverberation applied to coupled rooms.

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

Insertion loss between the receiver room and the source room

In this situation we compared the insertion loss (in dB) between the source and receiver rooms. This insertion loss is calculated by averaging the sound level inside each room for several configurations of the separation wall (including or not a door). This insertion loss can be compared to the theoretical value, obtained by applying the theoretical theory of reverberation to coupled rooms.

The results are given in the following table.

  • Note that the case R=0 dB (first results line) means that the door and the wall are perfectly transparent (no wall separation).
  • The value obtained using the theory and the SPPS simulations, always differ from the values R imposed on the door and on the separation wall, due the theory hypothesis and due to the estimation of the average sound level in a room using SPPS.
  • Except the case R=0 dB (the theory should not be used), one can observe a very good agreement between the theory and the SPPS simulations for all configurations.
R door (dB) R separation wall (dB) Theory

SPPS
(25/02/2010)

SPPS
(15/03/2017)

0 (transparent) 0 (transparent) 1,76 0,82 0,82
10 10 7,78 7,26 7,27
20 20 17,78 17,31 17,32
30 30 27,78 27,10 27,41
Closed & No transmission 10 8,11 7,59 7,61
10 No transmission 19,21 18,53 18,62
Open (R=0 dB) No transmission 9,65 9,25 9,29


Calculation parameters

ParametersValue
Active calculation of Atmospheric absorptionNO
Active calculation of diffusion by fitting objectsNO
Active calculation of direct field onlyNO
Active calculation of transmissionYES
Calculation methodRandom
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)1,5
Time step (s)0.01