Sound Energy Field in a System of Coupled Rooms

Abstract

The paper presents a theoretical basis of calculations of the sound intensity in enclosed spaces and shows results of numerical visualization of the active intensity in a room with absorptive walls formed by two coupled rectangular subrooms. The study was focused on the low-frequency range, therefore to describe the active and reactive intensities, the modal theory of room acoustics was applied. Space distribution of eigenfunctions, modal frequencies and modal damping coe cients were calculated numerically using the forced oscillator method (FOM) and the nite di erence time-domain (FDTD) method. Based on theoretical and numerical results, the computer program has been developed to simulate the active intensity vector eld when the room is excited by a harmonic point source. Calculation data have shown that the active intensity was extremely sensitive to position of the source since at a xed source frequency, di erent source locations always generate di erent distributions of characteristic objects of the active sound eld such as energy vortices and stagnation points. Because of complex room shape, the vortex centers are in most cases positioned irregularly inside the room. Almost regular arrangement of vortices was found only in the case when the source frequency was tuned to the frequencies of modes which were strongly localized in one of the subrooms.