DISCUSSION ON LDV SIGNAL PROCESSING FOR AIR-BORNE ACOUSTIC PARTICLE VELOCITY MEASUREMENT

Laser Doppler Velocimeter (LDV) is a non-intrusive measurement tool for fluid velocity. Acoustic particle velocity measured by LDV technique is one of the new primary methods to realize the air-borne sound pressure unit (Pascal) directly. When two coherent laser beams are crossed, the interference fringes appear. While particles moving through the fringes, they reflect the light into photomultiplier and lead to a doppler frequency shift. In acoustic field, how to process the doppler signal to obtain the acoustic particle velocity is one of the main issues of the measurement. In this paper, the existing signal demodulation methods for acoustic particle velocity are summarized, including the frequency tracking method, the doppler signal spectrum analysis method and the photon correlation method, etc. At last the applicability of different signal processing methods is discussed and an experimental test based on a commercial LDV system was carried out.