Low frequency sound energy decay in coupled volume rooms: results from a numerical study

In performance spaces, double sloped sound energy decays can be created intentionally to combine the two contradicting qualities clarity and reverberance. However, in office environments with atria, unintentional occurrence of double sloped decays might lead to noise nuisance.
This research focuses on the low frequency range. In contrast to the high frequency range, the double slope effect is expected to be frequency dependent for low frequencies. The low frequency sound field is simulated using the finite element method by solving the acoustic wave equation, for two rectangular rooms with varying location and distribution of apertures in the partition wall.
The results show a varying decay curve over different positions in the room, independent of the aperture location and distribution. The location of the apertures shows to have a large influence on the decay curve due to the modal shapes in the secondary room. A systematic frequency dependence of the decay curve has not been found but is likely to be present due to reduced aperture transparency at low frequencies. It is expected to be more distinctly present in larger volume room systems. Additionally the use of quantifiers to identify double sloped decay curves is discussed.