A comparison of two calibration methods for ultrasonic hydrophones

Although miniature ultrasonic hydrophones are frequently used to measure the acoustic pressure distributions from diagnostic ultrasound sources, relatively little attention has been devoted to the methods for absolute calibration of these hydrophones. In this study a polyvinylidene (PVDF) hydrophone was used to compare two calibration methods currently in use. One is based on a reciprocity technique and the second involves the planar scanning of a source transducer having a known radiated ultrasonic power. The reciprocity method revealed that the hydrophone response did not vary by more than +/- 1.6 dB from -262.8 dB re IV/microPa over the frequency range of 1-10 MHz. For the planar scanning technique seven ultrasound sources between 1-10 MHz were used, and all calibration points were within +/- 0.5 dB of the corresponding points found by the method of reciprocity.