Sound power measurements in non-ideal enclosures using acoustic energy density

Abstract

Sound power measurements are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. Reverberation chambers are used to approximate diffuse acoustic fields wherein the sound power is directly proportional to the spatially averaged squared pressure. Anechoic chambers are utilized to create a direct field condition, wherein sound power can also be determined from sound pressure levels located on a measurement surface which envelopes the source. This paper will introduce a method that utilizes acoustic energy density to estimate the sound power produced in non-ideal enclosures when both direct and reverberant energies contribute significantly to the total acoustic field. Since the acoustic energy density in an enclosure is more spatially uniform than the acoustic pressure, this method can achieve the same accuracy in determining sound power with fewer measurement positions when spatially averaging. The results from numerical models of several rectangular rooms of varying acoustical properties will be presented and the accuracy of the method will be addressed