Effect of background noise on sound power estimates using the sound intensity technique

Abstract

The presence of a background noise source affects the accuracy of the estimate of the source sound power level. In this paper, the results of a systematic experimental study on the accuracy of estimation of sound power levels in the presence of a background noise source are reported. A calibrated sound power source was used in these experiments. The sound power measurements were made using the two‐microphone sound intensity technique. The errors in the estimates of the sound power level of the calibrated sound source were determined for different levels of background noise. Also, a systematic study was made on the relationship between the number of points of measurement on the enclosing surface defined around the source and the accuracy of the sound power estimate. It has been demonstrated that the accuracy of sound power estimates is greatly improved by continuous hand scanning of the enclosing surface instead of by making measurements at a small or moderate number of fixed points. The local sound pressure minus intensity index and the global sound pressure minus intensity index are used as indicators of the data quality. [Work supported by IBM, Charlotte, NC.]