An experimental and computer study of the spatial distributions of p2 in a reverberant enclosure at low frequencies

Abstract

In a diffuse sound field the spatial distributions of p2 are exponential. Because in an enclosure the diffusion of the sound field is not perfect, it is necessary for some applications, such as the sound power measurements, to know how much the statistical distributions deviate from exponential, particularly at frequencies lower than the critical frequency fc = 2000 (T/V)1/2. Therefore, both computer and experimental studies were conducted from below the first mode in an enclosure up to and above the critical frequency in 1-Hz frequency increments with p2 calculated and measured in 120 spatial positions. Both probability density functions and cumulative distribution functions as well as the deviation from the exponential distributions were obtained. Computer-generated second order statistics have been investigated to determine the effect of a finite number of points used to generate the distributions. Based on the frequency dependence of the deviation of the actual distributions from the exponential distributions, it can be concluded that the reverberation room is usable from a lower frequency than fc.