A broadband pulse sound source passive ranging method based on dual hydrophones in unknown ocean environment

Abstract

The present invention is a broadband pulse sound source passive ranging method based on dual hydrophones in an unknown marine environment, including receiving a receiving signal of a broadband pulse sound source by two horizontally placed hydrophones; separating and extracting the simple normal wave signals contained in the sound pressure signals received by the two hydrophones respectively; performing cross-correlation processing on adjacent two-order simple normal waves, and obtaining the frequency domain phase difference by jointly processing the simple normal wave signals of the sound pressure signal; performing linear fitting on the phase differences of different groups, and using the obtained slope value as the estimated value of the sound source distance, and the average value after multiple groups are calculated simultaneously as the final ranging result, so as to realize accurate passive ranging of underwater sound sources. The passive ranging method adopted by the present invention is applicable to most shallow sea environments, does not require any prior conditions of the marine environment, can realize passive estimation of the sound source in the case of unknown marine environment information, has high accuracy, low error, low cost and strong operability.

Description

Technical Field

[0001] The invention belongs to the field of underwater acoustic signal processing and analysis, and specifically relates to a broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment. Background Art

[0002] The passive ranging technology of underwater sound sources in shallow sea waveguides is affected by the complex characteristics of the ocean environment such as multipath and dispersion, and has always been the focus and difficulty in the field of hydroacoustic research. The traditional matched field processing (MFP) technology is the earliest and most widely used passive ranging technology for underwater sound sources. However, this technology not only requires multiple calculations of the copy sound field, which is very computationally intensive, but also relies heavily on the accuracy of the sound field model and the ocean environment parameters, which brings difficulties to practical applications; although the related sound source target positioning method that relies on the hydroacoustic array has high accuracy, it relies on the hydrophone array, has high production costs and is difficult to operate. Therefore, the passive ranging method of underwater sound sources that does not require accurate prior knowledge of the ocean environment and does not rely on the accuracy of the sound field model is a current research hotspot. The dispersion effect of shallow sea waveguides makes the simple normal wave signals of each order in the received signal contain a large amount of ocean environment information during propagation, which brings more possibilities for extracting waveguide environment parameters and realizing sound source positioning. Using simple normal wave separation techniques such as warping transform, it is possible to separate and extract simple normal wave signals of different orders, which provides a new idea for making full use of marine environmental information and reducing the dependence of ranging technology on marine environmental parameters. On this basis, domestic and foreign scholars have proposed many new methods for passive ranging of underwater sound sources. Compared with matching field processing technology, it only reduces the dependence on marine environmental parameters, but to a certain extent still requires certain prior knowledge of the marine environment. The application of a guiding sound source with a known distance can achieve more accurate ranging in an unknown environment, but the acoustic characteristics of the guiding sound source are inevitably different from those of the original sound source, and the sound field conditions cannot be completely guaranteed to be consistent during the propagation of the sound signal. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment. The ranging method does not rely on the prior conditions of the ocean environment and only uses the collected data to realize the passive ranging method of the sound source in the unknown ocean environment.

[0004] In order to achieve the above object, the present invention is achieved through the following technical solutions:

[0005] The present invention is a broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment, which comprises the following steps:

[0006] Step 1, in a shallow sea environment, the emitted sound source signal is a low-frequency broadband pulse signal, and its spectrum is S(f); the placed sound source is a low-frequency broadband pulse sound source, and the sound source can be placed at any position in the seawater; the seabed is a horizontally layered high-speed seabed;

[0007] Step 2: The sound signal emitted by the broadband pulse sound source must be transmitted over a long distance to reach the receiving point. The transmission distance r ≥ 5km. The received signal is received by two horizontally placed hydrophones with a spacing of d, that is, there are two receiving points, the receiving depth is any position in the water, and the received sound pressure is p1(f,r)p2(f,r+d);

[0008] Step 3, respectively use the signal processing technology warping transform to process the time domain signals of p1(f,r) and p2(f,r+d) to separate the simple normal wave signals of each order contained in p1(f,r) and p2(f,r+d). The frequency domain sound pressure signals p1(f,r) and p2(f,r+d) received by the two receiving points contain two-order or more separable simple normal wave signals. During the use of the warping transform processing technology, the estimated distance r′ can be used instead of the actual propagation distance r to separate the simple normal wave signals in the received frequency domain sound pressure signals p1(f,r) and p2(f,r+d).

[0009] Step 4: Use the inverse warping transform technology to process the separated simple normal wave signals of each order to obtain the frequency domain sound pressure of the simple normal wave signals of each order. and Where n = 1, 2, 3, ..., the distance used by the inverse warping transform is the estimated value r', thereby eliminating the process quantity r' in obtaining the frequency domain sound pressure of each order of simple normal wave signals and Impact of the process;

[0010] Step 5: The initial phases of different-order simple normal wave signals are different, but the initial phases of two adjacent orders can be approximately equal. After cross-correlation processing, the frequency domain phase difference Δθ of the two-order simple normal waves related to the propagation distance is obtained by eliminating the polarity using the reference frequency f0. nm (f,f0,r), the obtained frequency domain phase difference Δθ nm (f,f0,r) is the frequency domain phase difference between two adjacent order simple normal wave signals;

[0011] Step 6: By calculating the same order normal wave signals in p1(f,r) and p2(f,r+d) and Perform cross-correlation processing to obtain the cross-correlation results of multiple groups of simple normal wave sound pressures of the same order In step 6, the frequency domain phase difference Δθ of the two-order simple normal waves is obtained.nm The order of the simple normal wave corresponding to (f,f0,d) and the frequency domain phase difference Δθ obtained in step 5 nm The simple normal wave orders corresponding to (f, f0, r) are consistent;

[0012] Step 7: Cross-correlation results of sound pressure of different-order simple normal waves Cross-correlation processing is performed again, and the frequency domain phase difference Δθ of the two-order simple normal waves related to the spacing d is obtained by eliminating the polarity using the reference frequency f0. nm (f,f0,d). The reference frequency f0 is the frequency contained in the bandwidth of all the simple normal wave signals used, and its value is not unique;

[0013] Step 8, based on The phase difference Δθ for different groups nm (f,f0,r) and Perform a linear fit, where Δθ nm (f,f0,r) and The specific method of linear fitting can be the least squares linear fitting method, based on and The slope r obtained by linear fitting x is the estimated value of the propagation distance r; in order to ensure the accuracy of the passive ranging result, the average value of the combined processing results of multiple groups of simple normal wave signals should be selected as the final ranging result.

[0014] The beneficial effects of the present invention are as follows: the present invention can be applied to unknown marine environments, does not require prior knowledge of the environment and does not require a guiding sound source; directly processes the received sound field signal, does not require the establishment of a sound field model, and effectively avoids the ranging error caused by the mismatch of the sound field model parameters; and only requires two hydrophones, which is low in cost, strong in operability and high in accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 4 is a flow chart of a passive ranging method in an embodiment of the present invention.

[0016] Figure 2 Schematic diagram of the application environment in the embodiment of the present invention.

[0017] Figure 3 1 is a time domain sound pressure signal of two receiving points and its correlation diagram in an embodiment of the present invention.

[0018] Figure 4 Detailed calculation flow chart of the simple normal wave phase difference in the embodiment of the present invention.

[0019] Figure 5 Graph showing the linear relationship between phase differences of different groups of normal wave signals in an embodiment of the present invention.

[0020] Figure 6 1 is the fitting of the phase difference of different groups of simple normal wave signals in the embodiment of the present invention.

[0021] Figure 7 1 is the fitting result of the phase difference of the same group of simple normal wave signals at different distances in the embodiment of the present invention.

[0022] Figure 8 1 is a comparison result between the estimated distance value and the actual distance value at different distances in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will disclose the embodiments of the present invention with drawings. For the purpose of clear description, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. That is to say, in some embodiments of the present invention, these practical details are not necessary.

[0024] The present invention discloses a broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment. The broadband pulse sound source passive ranging method comprises the following steps:

[0025] Step 1: Place a sound source in a shallow sea environment to transmit a sound source signal. The transmitted sound source signal is a low-frequency broadband pulse signal with a spectrum of S(f). The sound source is placed at any position in the seawater, and the propagation channel is a horizontally layered high-speed seabed.

[0026] Step 2: The sound source signal in step 1 is received by two horizontally placed hydrophones after propagating over a long distance r in a shallow sea environment, where r≥5km and the distance between the two hydrophones is d. The time domain sound pressure signals received by the two hydrophones are P1(t,r) and P2(t,r+d), respectively. After Fourier transform, frequency domain sound pressure signals p1(f,r) and p2(f,r+d) containing simple normal wave signals are obtained; t is time, f is frequency, and the frequency domain sound pressure signals p1(f,r) and p2(f,r+d) respectively contain two-order or more separable simple normal wave signals.

[0027] Step 3: Taking the estimated distance r′ as the estimated distance, the time domain signals of the frequency domain sound pressure signals p1(f,r) and p2(f,r+d) in step 2 are processed by using the signal processing technology warping transformation to separate the simple normal wave signals of each order contained in the frequency domain sound pressure signals p1(f,r) and p2(f,r+d) in step 2.

[0028] Step 4: Use the inverse warping transformation technology to process the simple normal wave signals of each order separated in step 3 to obtain the frequency domain sound pressure of the simple normal wave signals of each order. and n=1,2,3,…。

[0029] Step 5: For two adjacent order simple normal waves in the frequency domain sound pressure signal p1(f,r) After cross-correlation processing, the frequency domain phase difference Δθ of the two-order simple normal waves related to the propagation distance is obtained by eliminating the polarity using the reference frequency f0. nm (f, f0, r); the frequency domain phase difference Δθ obtained in step 5 nm (f,f0,r) is the frequency domain phase difference between two adjacent order simple normal wave signals.

[0030] Step 6: By comparing the same order normal wave signals in p1(f,r) and p2(f,r+d) and Perform cross-correlation processing to obtain the cross-correlation results of multiple groups of simple normal wave sound pressures of the same order

[0031] Step 7: Cross-correlation results of the sound pressure of different-order simple normal waves in step 6 Cross-correlation processing is performed again, and the frequency domain phase difference Δθ of the two-order simple normal waves related to the spacing d is obtained by eliminating the polarity using the reference frequency f0. nm (f,f0,d), where f0 is the frequency contained in the bandwidth of all the simple normal wave signals used, and its value is not unique. The frequency domain phase difference Δθ of the two-order simple normal waves obtained in this step is nm The order of the simple normal wave corresponding to (f, f0, d) and the frequency domain phase difference Δθ obtained in step 5 nm The simple normal wave orders corresponding to (f,f0,r) are consistent.

[0032] Step 8: Basis The phase difference Δθ for different groups nm (f,f0,r) and Linear fitting is performed, and the average value of multiple groups calculated simultaneously is the final distance measurement result.

[0033] The linear fitting method is but not limited to the least squares linear fitting method. and The slope r obtained by linear fitting x is the estimated value of the propagation distance r.

[0034] like Figure 2 As shown, in a shallow sea environment with a depth of H, the sound speed on the seabed is higher than the sound speed in the seawater. The transmitting transducer transmits the sound signal, and the receiving points 1 and 2 are placed horizontally with an interval of d. The horizontal distance between the sound source and the receiving point 1 is r.

[0035] Taking a broadband linear frequency modulation pulse signal as an example, the implementation process of the simple normal wave determination method of the present invention is as follows:

[0036] Assume that both receiving points are located on the seabed, and a broadband pulse sound source is emitted by the sound source transmitter, which is also located on the seabed. The sea depth is H = 100, the average sound speed in the seawater is 1500m / s, the sound speed on the seabed is 1650m / s, the distance between the two receiving points is d = 3km, and the horizontal distance between the sound source and the first receiving point is r = 15km.

[0037] Figure 3 The figure shows the time domain sound pressure signals of two receiving points and their correlation diagram. The two sound pressure signals are received by different receiving points. From the correlation diagram, it can be seen that the time delay t0 = 1.98s corresponds to the strongest correlation between the two. When the speed of sound in seawater is c0 = 1500m / s, the time delay caused by the interval d between the two is t1 = d / c0 = 2.0s. The two times are almost the same, which shows that for the two horizontally placed hydrophones, the time delay of the received sound pressure signals is mainly caused by their interval.

[0038] Figure 4 The figure shows the calculation flow chart of the simple normal wave phase difference. Figure 4 The steps are to process two groups of received sound pressure signals at a distance of r = 15 km from the sound source and r + d = 13 km from the sound source, extract the frequency domain sound pressure signals of the first five simple normal waves, select different adjacent simple normal wave signals for processing according to the four combinations (1, 2), (2, 3), (3, 4), and (4, 5), and finally obtain the phase difference combination (Δθ 12 (f,f0,r),Δθ 12 (f,f0,d))、(Δθ 23 (f,f0,r),Δθ 23 (f,f0,d))、(Δθ 34 (f,f0,r),Δθ 34 (f,f0,d))、(Δθ 45 (f,f0,r),Δθ 45 (f,f0,d)), using the four sets of data obtained, according to Linear fitting of the relationship.

[0039] Figure 5 The figure shows the relationship between the phase differences of different groups of simple normal waves, which is given by Figure 5 It can be seen that Δθ mn (f,f0,r) and Δθ mn The relationship between (f, f0, d) is periodic, but each period shows a linear relationship with the same slope. It can be seen that the slope between the two is That is, θ mn (f,f0,r) and The linear slope of is the distance r.

[0040] like Figure 6 As shown, select Figure 5 The linear fitting is performed on any periodic data in the figure to obtain the slope of the straight line, and the slope value is the estimated distance. It can be seen that when different sets of data are used for calculation, the estimated value is close to the actual distance r = 15km, and the estimated value is relatively accurate.

[0041] like Figure 7 The figure shows the data fitting results when using 1st and 2nd order simple normal waves to estimate the distance at different distances from 5km to 27km. The slope increases with the increase of distance, but the linear relationship between the phase differences remains unchanged.

[0042] like Figure 8 As shown, at different distances of 5km to 27km, the results of distance estimation using 1st and 2nd order simple normal waves are compared with the actual distances, and the two are consistent, which proves the effectiveness of the present invention in distance measurement.

[0043] The distance measurement method of the present invention adopts two horizontally placed hydrophones, has low cost, convenient operation and fast calculation speed, does not require prior knowledge of the ocean environment, and is suitable for broadband pulse sound sources in shallow sea waveguides with high sound speed horizontal seabed.

[0044] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment, characterized by: The broadband pulse sound source passive ranging method comprises the following steps: Step 1: Place a sound source in a shallow sea environment to emit a sound source signal. The emitted sound source signal is a low-frequency broadband pulse signal, and its spectrum is S(f); Step 2: The sound source signal in step 1 is received by two horizontally placed hydrophones after being propagated over a long distance r in a shallow sea environment. The distance between the two hydrophones is d. The time domain sound pressure signals received by the two hydrophones are P1(t, r) and P2(t, r+d), respectively. After Fourier transformation, frequency domain sound pressure signals p1(f, r) and p2(f, r+d) containing simple normal wave signals are obtained. Step 3: respectively process the time domain signals of the frequency domain sound pressure signals p1(f,r) and p2(f,r+d) in step 2 by using the signal processing technology warping transformation, so as to separate the simple normal wave signals of each order contained in the frequency domain sound pressure signals p1(f,r) and p2(f,r+d) in step 2; Step 4: Use the inverse warping transformation technology to process the simple normal wave signals of each order separated in step 3 to obtain the frequency domain sound pressure of the simple normal wave signals of each order. and Step 5: For two adjacent order simple normal waves in the frequency domain sound pressure signal p1(f,r) After cross-correlation processing, the frequency domain phase difference Δθ of the two-order simple normal waves related to the propagation distance is obtained by eliminating the polarity using the reference frequency f0. nm (f,f0,r); Step 6: By comparing the same order normal wave signals in p1(f,r) and p2(f,r+d) and Perform cross-correlation processing to obtain the cross-correlation results of multiple groups of simple normal wave sound pressures of the same order Step 7: Cross-correlation results of the sound pressure of different-order simple normal waves in step 6 Cross-correlation processing is performed again, and the frequency domain phase difference Δθ of the two-order simple normal waves related to the spacing d is obtained by eliminating the polarity using the reference frequency f0. nm (f,f0,d), where f0 is the frequency contained in the bandwidth of all the simple normal wave signals used, and its value is not unique; Step 8: Basis The phase difference Δθ for different groups nm (f,f0,r) and Linear fitting is performed, and the average value of multiple groups calculated simultaneously is the final distance measurement result.

2. According to claim 1, the broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment is characterized by: The frequency domain sound pressure signals p1(f, r) and p2(f, r+d) in step 2 respectively contain separable normal wave signals of two orders or more.

3. The broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment according to claim 2 is characterized by: In step 2, the propagation distance r≥5km.

4. According to claim 1, the broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment is characterized by: The frequency domain phase difference Δθ obtained in step 5 nm (f,f0,r) is the frequency domain phase difference between two adjacent order simple normal wave signals.

5. According to claim 1, the broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment is characterized by: The frequency domain phase difference Δθ of the two-order simple normal waves obtained in step 7 nm The order of the simple normal wave corresponding to (f, f0, d) and the frequency domain phase difference Δθ obtained in step 5 nm The simple normal wave orders corresponding to (f, f0, r) are consistent.

6. The broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment according to claim 1 is characterized by: In step 8, according to Δθ nm (f,f0,r) and The slope r obtained by linear fitting x is the estimated value of the propagation distance r.

7. The broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment according to claim 1 is characterized by: The sound source in step 1 is a low-frequency broadband pulse sound source, the sound source is placed at any position in the seawater, and the propagation channel is a horizontally layered high-speed seabed.

8. The broadband pulse sound source passive ranging method based on dual hydrophones in an unknown ocean environment according to claim 1 is characterized by: The linear fitting in step 8 is but not limited to the least squares linear fitting method.

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