Comparison of surface velocity measurement using a scanning laser vibrometer and acoustic holography.

Abstract

A significant amount of interest exists in performing noncontacting full-field surface velocity measurement. For many years traditional surface velocity measurements have been made by using a scanning Doppler laser vibrometer (SDLV). Nearfield acoustical holography is another approach that enables reconstruction of quantities such as the acoustic pressure, surface velocity, intensity, and power radiated from a structure into three-dimensional space, based on the sound pressure measured at a two-dimensional surface. Within this work the surface velocity of a clothes dryer panel is computed based on the acoustic field pressure measurements by using the Helmholtz equation least square (HELS) method, in which the reconstructed sound field is optimized by using spherical wave functions. The dryer panel is measured using an SDLV as well as a 64-channel microphone array. The reconstructed full-field surface velocity using the HELS method is compared to the measurement from the laser vibrometer during operation and also at discrete resonant frequencies.