METHOD FOR MEASURING HYDROPHONE SENSITIVITY IN SEA Russian patent published in 1998 - IPC

FIELD: acoustics. SUBSTANCE: method is based on calibration of hydrophone in low-frequency range using its comparison to reference hydrophone of known sensitivity γ_o. It involves submerging tested and reference hydrophones to different depths, spacing sound source and both tested and reference hydrophones by at least five sea depths. Relative position of reference and tested hydrophones which conforms to this condition provides difference of sound pressure in interference maximums below 1 dB. Calibration procedure involves rectilinear movement of sound source with low constant speed v (v/c < 2•10^-3, where c is velocity of sound in water), measuring average amplitude levels of signals at outputs of tested and reference hydrophones for time interval ΔT, which is equal to 8/3•H²/ λu, where H is sea depth, λ is wavelength of sound, detection of moments when instantaneous values of amplitudes are simultaneously greater than their average level. Tested hydrophone sensitivity γ_r is calculated using equation , where u_o(t_i) is amplitude of signal at output of reference hydrophone in moments t_i, i=1, 2, ..., M, when instantaneous amplitude levels are greater than average level, is signal amplitude at output of tested hydrophone in moments , i=1, 2, ..., M; j_o is number of samples for shifting tested hydrophone signal with respect to reference hydrophone signal. EFFECT: increased field of application. 3 dwg