Review of LDA and PIV applied to the measurement of sound and acoustic streaming

A review of laser Doppler anemometry (LDA) and particle image velocimetry ( PIV) with their application to the measurement of sound is presented. The f undamental principles behind LDA and PIV are discussed and extended to the application of sound measurement. Special attention is paid to analysis of LDA signals including the Hilbert transform, which enables amplitude inform ation to be obtained about various frequency components of a signal and wav elet analysis. which allows non-stationary signals to he accurately analyse d. The influence of the refractive index variations in a medium due to a so und wave on the laser beams of an LDA signal is discussed. Attention is als o paid to acoustic streaming which arises due to high-intensity sound, and PIV results are presented to demonstrate the effect. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.