Transmission loss measurements using a scanned array nearfield acoustical holography system in an anechoic/reverberation facility. Part II. Comparison of transmission loss methods.

Abstract

Transmission loss is an important metric used to assist in the selection of materials for noise control and design. In order to assess and improve the performance of transmission loss measurements, two different techniques were compared: traditional microphone and/or matched pair microphone intensity anechoic chamber-side techniques, and nearfield acoustical holography techniques. Intensity and sound power measurements using traditional methods were made on a test panel installed in an anechoic-reverb facility transmission loss window, then repeated using a conformal nearfield microphone array and nearfield acoustical holography processing techniques. The full vectored intensity components were used to assess the radiation characteristics of the test panel. This assessment quantifies the acoustics as panel radiation, flanking path contamination, and boundary effects. Data are presented to qualify the best estimate for transmission loss by rejecting contamination. Also, the dynamic range of the transmission loss measurement is compared between traditional and nearfield acoustical holography techniques with high transmission loss panel samples.