Phase calibration of hydrophones: heterodyne time-delay spectrometry and broadband pulse technique using an optical reference hydrophone

Two hydrophone calibration techniques are presented which provide amplitude and phase of hydrophone sensitivity. Heterodyne time-delay spectrometry can be applied in the frequency range from 0.5 to 50 MHz to all common hydrophones but needs a standard to obtain absolute values. A pulse technique between 1 and 70 MHz allows exploiting of an optical multilayer hydrophone as a phase standard. In combination with HTDS, a calibration service is established that covers the complete spectrum of common piezoelectric and optical hydrophones for absolute amplitude and phase calibration. The measured complex frequency responses form the basis of deconvolution procedures suitable for the correction of measurements of, for example, the output of ultrasound diagnostic machines.