Phase calibration of hydrophones by the free-field reciprocity method

Abstract

In this paper, a description is given of work carried out at the National Physical Laboratory to undertake phase response calibration of hydrophones by the free-field reciprocity method. A co-linear arrangement of hydrophones, based on the method of Luker and Van Buren, is used in order to eliminate some of the difficulties in the measurement of device separation and speed of sound in water. The experimental implementation of this method in the NPL open tank facility is described, along with the use of a laser alignment system to accurately set the position of the central hydrophone. The results of calibrations of three hydrophones are presented and these are compared to phase response measurements, performed on the same three hydrophones, using an optical vibrometry method, at Hangzhou Applied Acoustic Research Institute (HAARI) in China. © 2012 Acoustical Society of America.