RU97106235A - METHOD FOR DETERMINING HYDROPHONE SENSITIVITY IN MARINE CONDITIONS - Google Patents

Claims (1)

A method for determining the sensitivity of a hydrophone in marine conditions by comparing it with a reference one in the low frequency range, when the sound wavelength λ is in order of magnitude comparable to the sea depth H, which consists in generating harmonic signals of frequency f using a sound source and receiving a harmonic acoustic signal with calibrated and model hydrophones characterized in that the reception of a harmonic acoustic signal by calibrated and exemplary hydrophones is carried out in such a way that the immersion depths of the calibrated and braztsovogo hydrophone vary by an amount not greater than
λ [4π (1-n ² ) ^1/2 ] ^-1 ,
where n is the water-bottom refractive index, while the sound source is moved by a rectilinear tack with a constant low speed u at
v / c <2 • 10 ^-3 ,
where c is the speed of sound in water at a constant depth at horizontal distances between the source and the graduated hydrophone of large five depths of the sea, measured on a time interval ΔT equal to

the average levels of signal amplitudes at the outputs of the graduated and reference hydrophones, note those times when the current values of the signal amplitudes at the outputs of the calibrated and reference hydrophones exceed their average levels, and the reference sensitivity hydrophone γ _{o is} placed at a horizontal distance not exceeding the value
λ [(1-n) cosθ] ^-1 ,
where θ is the angle between the direction of movement of the source and the line connecting the calibrated and reference hydrophones, while the horizontal distance between the sound source and the model hydrophone should also exceed five depths of the sea, and the sensitivity γ _{g of the} calibrated hydrophone is determined by the mathematical ratio:

where U _o (t _i ) is the amplitude of the sound signal at the output of the exemplary hydrophone at times t _i , i = 1, 2, ..., M, when the current values of the amplitude exceed the average level,

the amplitude of the sound signal at the output of the calibrated hydrophone at time t _{i + jo} , i = 1, 2, ..., M,
moreover, the number of samples j _o by which it is necessary to shift the signal at the output of the graduated hydrophone relative to the signal at the output of the model hydrophone is determined by the minimum of the function:

where N _r is the starting point of the window;
m - the number of points in the window, which is selected from the condition
m • Δt ≥ 8 / 3H ² (λυ) ^-1 ,
Δt is the time interval between samples.