Temperature dependence of the sensitivity of hydrophone standards used in international comparisons

International comparison calibrations of hydrophone standards often involve the use of facilities with different water temperatures. Accurate comparison of the sensitivity values obtained in the different facilities then requires correction for the temperature dependence of the sensitivity. A hydrophone standard suitable for comparison calibrations was calibrated at temperatures from 5 °C to 35 °C in 5 °C steps. The calibrations were performed over the frequency range 5 kHz to 100 kHz in the Acoustic Pressure Tank Facility at the Underwater Sound Reference Division. The measured temperature dependence is much more complex than expected. Results are presented together with a discussion of possible contributions to this complexity.