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.
Boundary perturbarion 을 이용하여 Non-simple 한 Room의 파동 방정식을 풀었다.
또한 Room 의 특성을 알기위해 Simple harminic 음원과 Impulsive 음원에 대한 reverberant response 를 analytic하게 구하였다.
예로써 흡음재로 균일하게 처리된 직육면체의 Room (30' × 15' × 10') 에 휘장을 사용, Room 모양을 변화 시킨다고 생각했다.
이때 125 cycle에 중심을 둔 1/3-octave band pass filter를 사용한다고 가정, 시간에 대한 reverberant pressure 곡선을 그렸다.
또 그래프로 얻은 잔향시간을 Sabine 의 식으로 기산한 값과 비교하였다.