2F-1 Construction and Characterization of a Broadband Reference PVDF Membrane Hydrophone for Comparisons of Hydrophone Calibration Methods up to 140 MHz

A PVDF membrane hydrophone has been constructed in particular for comparisons of broadband ultrasound hydrophone calibration methods and for intercomparisons of different calibration laboratories. The hydrophone design chosen has a foil thickness of 9 mum and an electrode diameter of 210 mum. A very broadband differential preamplifier is integrated to achieve a high signal-to-noise ratio over a broad frequency range. The hydrophone was calibrated by means of a primary interferometric calibration technique in the range from 2 MHz to 60 MHz, by substitution calibration using time delay spectrometry in the range from 1 MHz to 40 MHz, and by complex broadband pulse calibration using nonlinear sound propagation in the range from 1 MHz to 140 MHz. The results show a very flat frequency response up to 40 MHz and a thickness mode resonance at about 105 MHz, and they indicate a useable bandwidth up to 140 MHz. The effective diameter as derived from directional response measurements is 240 mum at high frequencies