FMBEM simulation of the laboratory measurement of sound transmission loss in rectangular test rooms

In order to predict sound transmission loss of building elements, the fast multipole boundary element method is applied to simulate the laboratory measurement method in rectangular test rooms specified by ISO 10140-2 (JIS A 1416) for all the frequency bands from 100 to 4 kHz. Firstly, fine and simplified models are validated in comparison with theoretical and measured results for reference samples of membrane materials. Secondly, in addition to the sound pressure method, the sound intensity method is numerically simulated. As a result, it was shown that both models are applicable at mid and high frequency bands, but a simplified model overestimates the transmission loss more than a fine model at low frequency bands. Regarding the sound intensity method, the simulated values are lower than those with the sound pressure method, however approaching the theoretical values.