(A) theoretical study on room acoustics

Abstract

The acoustics of a rectangular room having geometrical irreqularities, whose walls have been covered by an absorbing material, is studied theoretically. Using Green``s functions a general equation for the pressure distribution is derived and this integral equation is solved approximately by perturbation method. By the use of Laplace transform and residual theorem, the transient pressure-time histories are obtained for a simple harmonic source and for an impulsive source. As an unperturbed example, a rectangular room of dimensions 30`` × 15`` × 10`` is considered. When the boundary shapes are perturbed, sound pressure is solved and its decay-curves are plotted within 1/3-octave band centered at 125 cycles/sec. Also wave-acoustical result is compared with that of geometrical acoustics by the reverberation time. Our method is general ; it is applicable to any form of irregularities if the amount of distortion is small and provided unperturbed solution are attainable.