Prediction and Modification of Broadband Interior Noise in Enclosures Using Energy-Intensity BEM and Absorption Scaling

Enclosures with diffuse reflection boundaries are modeled with an energy-intensity boundary element method using uncorrelated broadband directional sources. Input power is assumed to enter the enclosure through the walls, which are also absorptive. An absorption-based perturbation analysis is used to analyze the spatial variation of the acoustic field, which is shown to obey certain scaling laws. A series expansion in terms of spatial-average absorption gives separate boundary integral problems at each order. For the primary spatial variation, the effects of the relative distributions of absorption and input power are linear and uncoupled. These distributions can be expressed in terms of constituent spatial modes corresponding to the ways absorption and input power can be distributed. These amplitudes can be adjusted to tailor the spatial variation subject to system constraints. Examples include how to distribute absorption to minimize sound levels in one location, or how to achieve a uniform interior field.