Active control of diffuse sound fields using generalized energy density.

Abstract

In enclosures, the total acoustic energy density (ED) has been shown both theoretically and experimentally to be more spatially uniform than the squared pressure. The generalized energy density (GED) has even more uniform properties than the acoustic energy density. In active noise control applications, the standard approach taken is to minimize the squared pressure response in the field. However, the use of ED as the minimization quantity has been demonstrated to yield improved performance in low modal density acoustic fields, often resulting in improved global attenuation. For diffuse acoustic fields (high modal density), local “quiet zones” can be achieved, with the volume of this quiet zone typically being characterized as a sphere with a diameter of about one‐tenth of a wavelength when the squared pressure is minimized. It has been found that this performance can also be improved through the use of GED. By controlling GED instead of squared pressure, one cannot only increase the size of the quiet zone but also decrease the acoustic power added into the system. Results will be shown to illustrate the improved performance.