A reciprocity calibration of hydrophones in a non-anechoic water tank: Method and realization

To measure the electroacoustic parameters of transducers in the continuous sound field in a limited water area, a reciprocity calibration method of hydrophones using a spatial sampling average method in a non-anechoic tank was developed. The sound propagation in the non-anechoic tank under the impedance boundary condition, with a sound source producing continuous sound, is introduced based on the Helmholtz equation and Green's function. The reciprocity constant is given using the spatial sampling average sound pressure, and the three-transducer reciprocity calibration procedure was established. The number of spatial sampling points, which must be not less than 6000, and the sampling configuration in the non-anechoic tank are determined. In the non-anechoic tank of 15 m × 9 m × 6 m, the sensitivity of the hydrophone in the frequency range of 250 Hz to 10 kHz was calibrated, and the largest discrepancy between the measurement results from the reciprocity calibration method in the non-anechoic water tank and the standard facility was 0.7 dB.