Modal density of sound pressure level in a room

Modal analysis of the sound field in a rectangular room at low frequencies, based on the physics of the modal sound field, is presented in this paper. The eigenfrequencies and the modal density, which can be calculated with the well-known formulas and obtained by the calculated characteristic sound pressure level for three rooms with the same volume but different dimensions, is analysed. One of the main conclusions are that the sound field is determined, not by all eigenfrequencies that can be excited in the room, but only by extremely excited modes in a given band. Because of that, the spatial distribution of the sound field is a practically determined by these modes.