Residual pressure intensity index and performance evaluation of instruments to measure sound intensity

Abstract

Residual pressure intensity index measurements and performance evaluation of sound intensity probes and analyzers are discussed. The residual pressure intensity index was determined separately for the analyzers using identical electrical input signals, and for probe and analyzer combinations using identical sound-pressure inputs. Both FFT and digital frequency analyzers were examined in the investigations. The results show that the residual pressure intensity index depends on the input signal levels, and any phase compensation scheme should be considered in relation to these measurements. Performance of the probes was examined using a gating technique in a large enclosed space. The measured sound intensity levels using the sound intensity probe were compared with the levels derived from sound-pressure measurements from a single standard microphone. The results are in agreement with the predicted performance. Further discussions in the paper include the directivity of the probes and phase compensation schemes.