Determination of the Variation in Free-Field Hydrophone Response with Temperature and Depth

Author： Beamiss G. A. Robinson S. P. Hayman G. Esward T. J.

ISSN： 0001-7884

Source： Acta Acustica, Vol.88, Iss.5, 2002-09, pp. : 799-802

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

Data describing the variation in performance of commercially available hydrophones with temperature and depth have until now been difficult to obtain and are not readily available from manufacturers. The performance parameters, such as frequency response, electrical impedance and directional response, are important when one wishes to relate measurements made using the hydrophone in the marine environment to the free-field calibration obtained in a laboratory tank. The NPL Acoustic Pressure Vessel (APV) enables transducer performance parameters to be determined under simulated ocean conditions. Using the APV, free-field calibrations of hydrophones and projectors may be undertaken in the range from a few kilohertz to 1 MHz at water temperatures from 2°C to 35°C, and at applied hydrostatic pressures of up to 7 MPa (simulating ocean depths of up to approximately 700 m). The operation of the APV and the methodology used to characterise hydrophones are presented in this paper. Also presented are the results of the characterisation of a number of commercially available hydrophones as a function of temperature and applied hydrostatic pressure. The results show a strong dependence of performance on environmental conditions for some devices. Sensitivity variations of several decibels have been observed as the hydrostatic pressure is increased to 7 MPa, with variations also observed as the water temperature is changed. For some hydrophones, the variation in electrical impedance with temperature and applied pressure can be shown to correlate well with the variation observed in the absolute sensitivity.