Based on computer simulations of sound fields in rectangular enclosures, important observations are made regarding sound pressure levels and the spatial variation of the broadband reverberant field. From these observations an empirical formula is deduced that describes the slow spatial variation of the broadband reverberant mean-square pressure in one lengthwise direction. Two room shapes were studied: an elongated rectangular enclosure and an almost cubic enclosure, both with broadband sound source(s) on an endwall. Source position, relative phasing of multiple sources, level, and placement of absorptive material were variables in the study. The numerical results for the spatially averaged mean-square pressure in the reverberant field were often not in very close agreement with values predicted from a traditional Sabine approach. The prediction was improved by accounting for the power absorbed on the first reflection and an approximate formula is given for this correction factor. The reverberant sound field is characterized by a gradual spatial variation in the direction away from the source. This spatial variation scales exponentially with the sidewall absorptivity, as demonstrated by the numerical simulations. An approximate emperical formula is shown to predict this spatial variation fairly well. The computer simulations showed elevated sound pressure levels at the enclosure boundaries, for all cases, and also in the interior, for sound fields excited by a single broadband source on an endwall. These intensification zones occur along a plane in front of the source and along a plane which corresponds to the reflection of the source, whether or not the source is on a line of symmetry.

The effect of the spatial distribution of absorbing surfaces on the sound field in enclosures is investigated. For a given overall level of absorption, the difference between distributing the absorption uniformly or localizing it in a single region is studied. Attention is focused on the high-frequency range having wavelengths small compared to the enclosure dimensions, but either large or small compared to the absorptive region. The distribution of mean-square pressure in a bandwidth is studied to ascertain the degree of uniformity throughout the enclosure, and particularly in the vicinity of the absorbing region. Of special interest is the effect of absorption on intensification zones, which are the regions near boundaries where there is a high degree of spatial correlation between modes. Depending upon the amount of absorption, the center frequency wavelength and/or the dimensions of the absorber are used to determine the size of nonuniform regions in the enclosure. The study is conducted using classical modal analysis. The results provide physical insight into the behavior of acoustic fields in enclosures.