The most popular instrument for making underwater ultrasound measurements is the hydrophone. However, this device brings several disadvantageous features about. Since a hydrophone has to be submerged into the fluid, where the wave propagates, the device itself perturbs the measured sound field. The receiver will produce an integrative effect on the measured quantity, if the receiver size is not significantly smaller than the wavelength. A variety of optical metrology techniques have been developed in the attempt to overcome the problems associated with hydrophones. Harland et al. investigated the application of laser Doppler velocimetry, a technique based on detecting a Doppler shift in coherent laser light of an optical interferometer, for ultrasonic measurements and demonstrated the high sensitivity of the method. Compared to the NPL Laser interferometer, which is the primary calibration standard in the UK for measurements conducted in the frequency range 500 kHz to 20 MHz, the method showed equally good results. Kristen used laser Doppler velocimetry to measure the pressure amplitude of standing waves in a tube. Zipser et al. made measurements of acoustic waves and turbulences in a 2D-plane. We describe a technique for 3D sound pressure measurements using a customary laser Doppler vibrometer in conjunction with post processing the data with the computed tomography method.
Computed tomography applied to interferometric ultrasonic field measurements in fluids
Computertomographie angewendet auf interferometrische Ultraschallfeldmessungen in Fluiden
2006
6 Seiten, 4 Bilder, 7 Quellen
Conference paper
English
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