European comparison of ultrasonic hydrophone calibrations

Abstract

A European comparison of 1 mm hydrophone calibrations in the frequency range 0.5 MHz to 15 MHz is summarized. The project, organized by the Bureau Communautaire de Reference (BCR) of the Commission of the European Communities, involved five participants from different countries measuring the free-field sensitivity of three types of miniature ultrasonic hydrophone. Three different absolute calibration methods were used in the project, which was completed and published in 1991. The uncertainties quoted at the 95% confidence level ranged from 2.3% to 18%, depending on the frequency, method and laboratory. Agreement between laboratories was generally within a few parts in 102 in the range 0.5 MHz to 5 MHz but individual results differed by up to 15% from the grand mean at 10 MHz and 15 MHz.