A method for predicting sensitivity of spherical hydrophones at high hydrostatic pressures and its experimental validations.

A method for predicting sensitivity of spherical hydrophones at high hydrostatic pressures is developed based on their impedances without acoustic environments. In this approach, the receiving performance of a spherical hydrophone is modelled as an equivalent circuit, and the relationship between the sensitivity and the parameters of the equivalent circuit is established. To accurately obtain these parameters, these impedances of spherical hydrophones at different hydrostatic pressures are measured, and the parameter matrix of the equivalent circuit is evaluated by the nonlinear evaluation solution of the Levenberg-Marquardt algorithm. The evaluated parameter matrix is applied to calculate the sensitivity of spherical hydrophones. To examine the validity of this method, the sensitivities of the spherical piezoelectric hydrophones of RHS 30 and RHS 20 were predicted at hydrostatic pressures from 2 to 8 MPa and compared with the measured results by free-field measurement facility in a vessel. The predicting results agreed well with the measured ones with the maximum deviation less than 8% in the operation frequency range. In addition, the advantages and limitations of this method are discussed. This method is promising in the study of measuring deep ocean performances of hydrophones in a laboratory.