The Measurement of Sound Fields Using Laser Doppler Anemometry

Methods of analysis for the study of sound fields are outlined and their fundemental limitations discussed. The spectral analysis and the correlation analysis method are shown to have the same limitations in the analysis of sound fields, since they are time averaged methods of analysis. This limits the use of these techniques to simple situations such as a monotonic sound field. The frequency tracking method, although it is dependent on heavy seeding, is shown by the use of a theoretical model, to allow the measurement of the acoustic particle velocity and the frequency of the sound field components for more complex situations. The possibility of obtaining the phase difference between the components is also discussed.