Towed noise measurement method based on wave number spectrum integration

Abstract

The invention discloses a towed noise measurement method based on wavenumber spectrum integration, which comprises the following steps of: converting array element domain data into a frequency wavenumber domain through two-dimensional Fourier transform of a spatial domain to obtain a frequency wavenumber spectrum; wave number domains of towed platform noise and non-towed platform noise are determined according to actual towed conditions, and average power spectrums of platform area noise and non-platform area noise are respectively calculated based on the corresponding wave number domains; estimating a towed platform noise spectrum through an average power spectrum statistical result of platform area noise and non-platform area noise of continuous frames; and subtracting the towed platform noise spectrum from the average power spectrum of the array element domain to obtain a towed line array towed noise spectrum.

Description

Technical Field

[0001] The invention belongs to the field of towed array towed noise measurement, and in particular relates to a towed noise measurement method based on wavenumber spectrum integration. Background Art

[0002] When measuring the towed array noise, the winch towing rope pulls the unpowered boat, which moves the towed array in the water. There will be system noise at the bow of the unpowered boat, and the noise level of the towing system will increase with the increase of speed. The interference caused by the towing system seriously affects the numerical measurement results and affects the designers' judgment on the performance of the towed array equipment.

[0003] The existing towing noise measurement method generally directly performs power spectrum analysis on the test data to obtain the average power spectrum, which is the towing noise spectrum. However, the measurement accuracy of this towing noise measurement method is not high, which often affects the judgment of the personnel involved in the towing array equipment performance. Summary of the invention

[0004] The object of the present invention is to provide a drag noise measurement method based on wavenumber spectrum integration to solve the problems raised in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A dragging noise measurement method based on wave number spectrum integration, the method comprising: converting array element domain data into frequency wave number domain by two-dimensional Fourier transform in spatial domain to obtain frequency wave number spectrum;

[0007] According to the actual towing situation, the wave number domains of the towed platform noise and the non-towed platform noise are determined, and the average power spectra of the platform area noise and the non-platform area noise are calculated based on the corresponding wave number domains.

[0008] The noise spectrum of the towed platform is estimated by the statistical results of the average power spectrum of the platform area noise and the non-platform area noise of continuous frames;

[0009] The towed array noise spectrum is obtained by subtracting the towed platform noise spectrum from the average power spectrum in the array element domain.

[0010] Preferably, the step of acquiring the frequency wavenumber spectrum comprises:

[0011] After starting the test at the set speed, the towed array towed noise data is collected and processed with a Hanning window to obtain the time domain data X of each array element. m (t), where m is the array element number and t is the time series;

[0012] Get each time domain data X m(t) The data of each sound channel within the working frequency band of the equipment is obtained by checking the speed information of the real-time speed measuring equipment in the towing boat. The signal acquisition personnel mark the time period of stable speed in the test data, and perform power spectrum analysis on the data of the stable time period of the towing state to obtain the spectrum X of each sound channel. m (f);

[0013] Construct the spatial wave number vector w(k)=[w 1 (k), ..., w m (k), ..., w M (k)], where k is the wave number;

[0014] The spatial wave number vector and the acoustic channel spectrum are used to perform a two-dimensional Fourier transform to obtain the frequency wave number spectrum result P(f, k).

[0015] Preferably, the step of determining the integration interval of the platform noise according to the actual towing situation includes:

[0016] Calculate the wave number lower limit of platform interference f is the frequency, θ is the angle of the winch platform relative to the bow of the towing array measured at the beginning of the towing test, and c is the speed of sound in water;

[0017] Calculate the upper limit of the wave number of platform interference

[0018] The wave number domain of the platform area noise is determined to be [kl, kh], and the wave number domain of the non-platform area noise is determined to be [2kl-kh, kl].

[0019] Preferably, the platform noise spectrum estimation step comprises:

[0020] The variance σ(PN) is calculated using the average power spectrum PN of the noise in the non-platform area of ​​the L frame;

[0021] Using the variance σ(P N ) platform noise analysis strategy to calculate the platform noise spectrum P ave (f);

[0022] The platform noise analysis strategy is:

[0023]

[0024] Among them, l is the frame index, α is the preset value, P 平台 () is the average power spectrum of the noise in the platform area.

[0025] Preferably, the average power spectrum X in the array element domain is s (f) Obtained by taking channel average in the array element domain.

[0026] Preferably, the average power spectrum X in the array element domain is s (f) Subtract the platform noise spectrum P ave (f) is the towed array towed noise spectrum expressed as X(f) = 10log 10 (X s (f)-P ave (f)).

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The towed array towed noise spectrum result calculated by the present invention can be closer to the noise level of the towed array itself when it is actually used. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of an embodiment of the present invention;

[0030] Figure 2 is the frequency wavenumber spectrum;

[0031] Figure 3 It is the wave number global integration result and the average power spectrum of the sound channel;

[0032] Figure 4 The power spectrum of platform area and non-platform area;

[0033] Figure 5 A visualization of the tow noise spectrum measurement results. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0035] This embodiment provides a drag noise measurement method based on wave number spectrum integration, and the method process is as follows:

[0036] The array element domain data is converted to the frequency wave number domain through a two-dimensional Fourier transform in the spatial domain to obtain a frequency wave number spectrum;

[0037] According to the actual towing situation, the wave number domains of the towed platform noise and the non-towed platform noise are determined, and the average power spectra of the platform area noise and the non-platform area noise are calculated based on the corresponding wave number domains.

[0038] The noise spectrum of the towed platform is estimated by the statistical results of the average power spectrum of the platform area noise and the non-platform area noise of continuous frames;

[0039] The towed array noise spectrum is obtained by subtracting the platform noise spectrum from the average power spectrum in the array element domain.

[0040] The towed array towed noise spectrum measured by this method is closer to the noise level of the towed array itself when it is actually used.

[0041] Figure 1 The specific flow chart of the towed array towed noise measurement method based on wave number spectrum integration is shown. Figure 1 As shown, the towed array towed noise measurement method specifically includes the following steps:

[0042] Step 1: After starting the test at the set speed, collect the towed array towed noise data, and add the Hanning window H(t) to the towed noise data to obtain the time domain data X of each array element in the towed array. m (t), where m is the array element number and t is the time series.

[0043] Step 2: Get each time domain data X m (t) The data of each sound channel within the working frequency band of the equipment is obtained by checking the speed information of the real-time speed measuring equipment in the towing boat and selecting the data of the stable time period of the towing state for power spectrum analysis during data processing to obtain the spectrum X of each sound channel. m (f) and take the channel average in the array element domain to obtain the average power spectrum X s (f).

[0044] In step 2 of the present invention, power spectrum analysis is performed by discrete Fourier transform, as shown in the following formula:

[0045] X m (f) = DFT[X m (t) × H(t)]

[0046] Step 3: Construct the spatial wave number vector w(k) = [w 1 (k), ..., w m (k), ..., w M (k)], Where j is an imaginary number, k is the wave number, and m is the array element number. Using the spatial wave number vector w(k) and the acoustic channel spectrum X m (f), perform a two-dimensional Fourier transform in the spatial domain to obtain the frequency wavenumber spectrum result P(f, k).

[0047] The two-dimensional Fourier transform formula is as follows:

[0048]

[0049] Step 4, calculate the wavenumber upper limit kh and lower limit kl of the platform noise interference, and obtain the wavenumber domain of the platform area noise as [kl, kh], and set the wavenumber domain of the non-platform area noise to [2kl-kh, kl].

[0050] In the present invention, the platform noise in the wave number spectrum includes platform noise and non-platform noise, so it needs to be separated for accurate measurement. The wave number domain of the non-platform region is set to the same wave number width as the platform noise.

[0051] Here, the calculation formulas for the upper and lower wavenumber limits kh and kl of the platform noise interference are:

[0052]

[0053] During the test, the towing boat was at the bow of the towing array, i.e., 0°, and the interference within the frequency wavenumber spectrum sound cone was mainly considered. f represents the frequency, c is the speed of sound in water, c=1500m / s; θ is the angle of the winch platform relative to the bow of the towing array measured at the beginning of the towing test.

[0054] Step 5: Take the wave number domain as the integration area, integrate the frequency wave number spectrum in the wave number domain of the platform area noise, and obtain the average power spectrum P of the platform area noise. 平台 (f); At the same time, the frequency wavenumber spectrum is integrated in the wavenumber domain of the non-platform noise to obtain the average power spectrum P of the non-platform noise N (f).

[0055]

[0056] Step 6: By processing the data stream, the average power spectrum P of the platform interference noise of each frame is obtained. 平台 (l, f) and the average power spectrum P of the noise in the non-platform area N (l, f), l is the frame index, l = 1, ..., L; the platform noise spectrum P is calculated using the platform noise analysis strategy ave (f), the noise analysis strategy of the platform is as follows:

[0057]

[0058] Among them, σ(P N ) is the variance calculated using the average power spectrum of the non-platform area noise corresponding to L consecutive frames, where α=6dB.

[0059] In the present invention, the P calculated in step 5 is 平台 (f) It includes the towing noise and environmental noise components, and the average power spectrum estimation result in the non-towed platform noise area is used as the average power spectrum level of the towing noise and environmental noise in the platform area.

[0060] In step 6 of the present invention, if P 平台 =P N ≤σ(P N ), the influence of the dragging platform on the towing noise measurement result is considered to be negligible, and the element domain power spectrum can be calculated as the towing noise spectrum.

[0061] Step 7: Calculate the towed array noise spectrum using the average power spectrum in the array element domain and the platform noise spectrum. The calculation formula is as follows:

[0062] X(f)=10log 10 (X s (f)-P ave (f)).

[0063] In this embodiment, after calculation in step 3, the frequency wavenumber spectrum result P(f, k) is obtained as follows: Figure 2 As shown by Figure 2 It can be seen that there is a strong interference component in the wave number region from f / 2400 to f / 1450, which mainly comes from the noise interference of the towing test platform. The noise power spectrum of the platform area and the non-platform area is calculated by step 5 as follows: Figure 4 As shown, the towed array towed noise spectrum is finally obtained through step 7 as shown in Figure 5 shown.

[0064] In the present invention, the frequency wavenumber spectrum P(f, k) is integrated in the full wavenumber domain to obtain an average power spectrum, which is compared with the channel average power spectrum. The average power spectrum obtained by integrating the wavenumber spectrum coincides with the average power spectrum curve of the acoustic channel, as shown in FIG. Figure 3 As shown, the numerical calculation accuracy of the measurement method of the present invention is high.

[0065] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for measuring dragging noise based on wavenumber spectrum integration, characterized in that: The method comprises: converting array element domain data into frequency wave number domain by two-dimensional Fourier transform in space domain to obtain frequency wave number spectrum; According to the actual towing situation, the wave number domains of the towed platform noise and the non-towed platform noise are determined, and the average power spectra of the platform area noise and the non-platform area noise are calculated based on the corresponding wave number domains. The noise spectrum of the towed platform is estimated by the statistical results of the average power spectrum of the platform area noise and the non-platform area noise of continuous frames; The towed array noise spectrum is obtained by subtracting the towed platform noise spectrum from the average power spectrum in the array element domain.

2. The method for measuring dragging noise based on wavenumber spectrum integration according to claim 1, characterized in that: The step of obtaining the frequency wavenumber spectrum comprises: After starting the test at the set speed, the towed array towed noise data is collected and processed with a Hanning window to obtain the time domain data X of each array element. m (t), where m is the array element number and t is the time series; Get each time domain data Xm ( t) For each sound channel data within the working frequency band of the equipment, by checking the speed information of the real-time speed measuring equipment in the towing boat, the signal acquisition personnel marked the time period of stable speed in the test data, and performed power spectrum analysis on the data of the stable time period of the towing state to obtain the spectrum X of each sound channel m (f); Construct the spatial wave number vector w(k)=[w1(k),...,w m (k), ..., w M (k)], where k is the wave number; The spatial wave number vector and the acoustic channel spectrum are used to perform a two-dimensional Fourier transform to obtain the frequency wave number spectrum result P(f, k).

3. The method for measuring dragging noise based on wavenumber spectrum integration according to claim 1, characterized in that: The integral interval of determining the platform noise according to the actual towing situation includes: Calculate the wave number lower limit of platform interference f is the frequency, θ is the angle of the winch platform relative to the bow of the towing array measured at the beginning of the towing test, and c is the speed of sound in water; Calculate the upper limit of the wave number of platform interference The wave number domain of the platform area noise is determined to be [kl, kh], and the wave number domain of the non-platform area noise is determined to be [2kl-kh, kl].

4. The method for measuring dragging noise based on wavenumber spectrum integration according to claim 1, characterized in that: The platform noise spectrum estimation step includes: The average power spectrum P of the noise in the non-platform area of ​​L frame is used N Calculate the variance σ(P N ), using the variance σ(P N ) platform noise analysis strategy to calculate the platform noise spectrum P ave (f); The platform noise analysis strategy is: Among them, l is the frame index, α is the preset value, P 平台 () is the average power spectrum of the noise in the platform area.

5. The method for measuring dragging noise based on wavenumber spectrum integration according to claim 2, characterized in that: The average power spectrum X in the array element domain s (f) Obtained by taking channel average in the array element domain.

6. The method for measuring dragging noise based on wavenumber spectrum integration according to claim 1, characterized in that: The average power spectrum X in the array element domain s (f) Subtract the platform noise spectrum P ave (f) is the towed array towed noise spectrum expressed as X(f) = 10log 10 (X s (f)-P ave (f)).

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