Instrumentation for underwater acoustic intensity measurement

Abstract

Acoustic intensity is one of the most important quantities in underwater acoustics. The conventional way of obtaining the acoustic intensity is by using two microphones as an intensity probe. However, the finite difference approximation will bring errors to the intensity calculation. Moreover, few publications mention instrumentation for measuring underwater acoustic intensity, in spite of intensity measurements being more meaningful for underwater usage. The instrumentation for measuring underwater acoustic intensity is presented in this paper: the intensity probe is a pressure-acceleration based vector hydrophone from which the particle velocity can be obtained directly. Therefore, the errors due to finite difference approximation will be eliminated by using the vector hydrophone. To test the instrumentation, the acoustic intensity is measured in a standing wave tube. To measure the self-noise of the intensity probe, a facility called Self-Noise Evaluation System is also presented in this paper.