Robust sound transmission loss prediction with a hybrid finite element-statistical energy analysis method

When considering a wall in between two rooms, in an important part of the audio frequency range the local response of the rooms may be highly sensitive to uncertainty in spatial variations in geometry, material properties, boundary conditions, etc, while the local response of the wall is rather insensitive to such uncertainty. For this mid-frequency problem, a hybrid strategy is adopted that accounts for the uncertainty in the local room properties. The partition is modeled deterministically, with finite elements. The rooms are modeled in a very efficient, nonparametric stochastic way, as in statistical energy analysis. This strategy is extended so that not only the mean value of the sound transmission loss, but also the variance can be computed. A second extension allows computing band-averaged quantities in an efficient way. The method is then applied to a set of partitions of increasing complexity: a thin PMMA plate, a wall consisting of gypsum blocks and a thicker masonry wall. The results are compared with laboratory measurements, and it is found that the uncertainty caused by the random local room properties is well captured.