US 11,391,863 B2 · Method of free-field broadband calibration of hydrophone sensitivity based on pink noise

Abstract

A method of free-field broadband calibration of hydrophone sensitivity based on pink noise, relating to the field of free-field underwater acoustic measurement, and is mainly used for broadband measurements of hydrophone sensitivity in free-field. The method of the present disclosure is to transmit a broadband pink noise signal by controlling the signal source, and to perform the synchronous processing and FFT to the transmitted current signal and the received voltage signal, such as interception and zero padding, and finally obtain the transfer function in the frequency domain; by analyzing the direct wave and the reflected wave in the water tank, the transfer function is averaged by a rectangular window to eliminate the influence of the reverberation of the reflected wave in the water tank, so as to obtain the broadband transfer function of the free-field between the transmitting transducer and the hydrophone.

A method of free-field broadband calibration of hydrophone sensitivity based on pink noise comprising the following steps:

(1) generating a pink noise signal with a certain bandwidth according to a measurement frequency range, and performing a power amplification to the pink noise signal;
(2) exciting, by the pink noise signal after power amplification, a transmitting transducer to generate a sound signal underwater, receiving the sound signal by two hydrophones, wherein one of the two hydrophones is a standard hydrophone, whose sensitivity M0 is known, and the other one is the hydrophone under test, the sensitivity Mx of the hydrophone under test is to be measured;
converting the received sound signal into a corresponding voltage signal by the two hydrophones, respectively, performing impedance matching and pre-amplification on the corresponding voltage signal by a preamplifier, then performing anti-aliasing filtering on the corresponding voltage signal after amplification by a filter to obtain the open circuit voltage signal U0 corresponding to the standard hydrophone and the open circuit voltage signal Ux corresponding to the hydrophone under test;
(3) at the same time, performing current sampling on the pink noise signal after power amplification to generate a corresponding voltage signal U1 at a ratio of 1:1, inputting the voltage signal U1 to the preamplifier to conduct impedance matching and pre-amplification, and performing anti-aliasing filtering by a filter;
(4) storing the voltage signals U0 and Ux and the voltage signal UI obtained after current sampling in a computer;
(5) after repeating n times according to steps (1) to (4), obtaining n groups of open circuit voltage signals U01, U02, . . . , U0n of the standard hydrophone, n groups of open circuit voltage signals Ux1, Ux2, . . . , Uxn of the hydrophone to be tested and n groups of voltage signals UI1, UI2, . . . , UIn after current-sampled;
performing time delay processing to these signals respectively in the computer to obtain following voltage signals accordingly:
(U′01, U′02, . . . , U′0n, U′x1, U′x2, . . . , U′xn and U′I1, U′I2, . . . , U′In;
and then performing FFT (Fast Fourier Transform) calculation on these obtained signals to obtain the corresponding complex spectrum F01, F02, . . . , F0n, Fx1, Fx2, . . . , Fxn and FI1, FI2, . . . , FIn;
wherein n is a natural number and is greater than 1;
(6) averagely calculating the above complex spectrum in a frequency domain according to equation (1) to obtain the signals F0, Fx and FI after averaging the corresponding complex spectrum;
thereby obtaining a complex response function of the transfer impedance between the standard hydrophone and the transmitting transducer and the hydrophone under test with respect to the frequency f through the voltage signals, wherein the complex response function comprises random noise and reflected sound, as shown in equation (2):
F
0
=
F
01
+
F
02
+
…
+
F
0
⁢
⁢
n
n
⁢
⁢
F
x
=
F
x
⁢
⁢
1
+
F
x
⁢
⁢
2
+
…
+
F
x
⁢
⁢
n
n
⁢
⁢
F
I
=
F
I
⁢
⁢
1
+
F
I
⁢
⁢
2
+
…
+
F
I
⁢
⁢
n
n
(
1
)
Z
x
⁡
(
f
)
=
F
x
/
F
I
⁢
⁢
Z
0
⁡
(
f
)
=
F
0
/
F
I
(
2
)
wherein Zx(f) is the complex response function of the transfer impedance between the transmitting transducer and the hydrophone under test with respect to the frequency f, Z0(f) is the complex response function of the transfer impedance between the transmitting transducer and the standard hydrophone with respect to frequency f;
(7) performing complex moving average processing on the complex response function using a rectangular window in the frequency domain to obtain the complex transfer impedance between the transmitting transducer and the hydrophone under free-field conditions;
(8) under the premise that the sensitivity of the standard hydrophone is known, calculating the broadband sensitivity of the hydrophone under test according to the transfer impedance of the two hydrophones and the transmitting transducer under free-field conditions, as shown in equation (3):
M
x
⁡
(
f
)
=
201
⁢
⁢
g
⁢
Z
x
⁡
(
f
)
⁢
d
x
Z
0
⁡
(
f
)
⁢
d
0
+
M
0
⁡
(
f
)
(
3
)
wherein Mx(f) is the broadband sensitivity of the hydrophone under test at frequency f, M0(f) is the broadband sensitivity of the standard hydrophone at frequency f, and dx is the distance between the transmitting transducer and the hydrophone under test, d0 is the distance between the transmitting transducer and the standard hydrophone.

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Method of free-field broadband calibration of hydrophone sensitivity based on pink noise

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Method of free-field broadband calibration of hydrophone sensitivity based on pink noise

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Abstract

Claims7