CN103293515A - Ship and warship line spectrum noise source longitudinal distribution characteristic measuring method - Google Patents

Abstract

The invention provides a ship and warship line spectrum noise source longitudinal distribution characteristic measuring method. First of all, fast Fourier transform is conducted on collected hydrophone receiving signals to analyze frequency spectrum, micro-region signals with line spectrums are separated out, and a Doppler analyzing signal is obtained in a pluralized mode; the Doppler signal to be analyzed is obtained and WVD is conducted on the Doppler signal: the right-horizontal moment estimated value when each low frequency line spectrum noise source on a ship or a warship passes the measurement hydrophone is obtained; time difference of passing the right-horizontal moment of passing the measurement hydrophone of each noise source and a beacon source is utilized and is combined with ship and warship motion speed to determine the position of each noise source distributed on the ship and warship in a longitudinal mode. The ship and warship line spectrum noise source longitudinal distribution characteristic measuring method is simple to implement, and higher in measuring accuracy than a passing characteristic method.

Description

The vertical distribution character measuring method of a kind of naval vessel line spectrum noise source

Technical field

The present invention relates to signal handles and the underwater acoustic measurement field.

Background technology

The hydrodynamic effect that ship-radiated noise produces when being mainly derived from the main frame propulsion system, screw propeller, subsidiary engine mechanical system on naval vessel and navigation.Wherein, the line spectrum noise that is caused by the to-and-fro movement of subsidiary engine machinery has that frequency is low, power is high and stable characteristics such as strong, and it is carrying the important characteristic information in naval vessel, can is the key that underwater sound equipment is surveyed the naval vessel by long-range detection.Reduce ship noise and not only can reduce ship navigation to halobiontic influence, also be conducive to improve simultaneously the performance that is equipped in the various underwater sound equipments on the naval vessel.Therefore, the naval vessel noise reduction becomes the urgent task of naval vessel acoustic design, and the position of accurately identifying overriding noise source on the naval vessel provides reference and foundation for the acoustic design on naval vessel.

Measurement to ship-radiated noise in the past mainly utilizes it to realize by characteristic.When carrying out the radiated noise measurement, at the uniform velocity line navigation is done on tested naval vessel, draw near and also from the close-by examples to those far off leave measurement hydrophone near measurement hydrophone, measurement hydrophone records the sound pressure level (or power spectrum level) of tested ship-radiated noise and the corresponding relation of measurement hydrophone relative position in this process, generally is referred to as the characteristic of passing through of ship-radiated noise.Utilize undersea ranging information and the method for radiated noise synchronous recording can obtain position, naval vessel and radiated noise signals corresponding pass through family curve.Ship-radiated noise comprises that by characteristic overall level passes through characteristic, and the 1/3oct band level passes through characteristic by characteristic and line spectrum.Overall level is by the position of characteristic maximal value corresponding to naval vessel overall level maximum, and 1/3oct sound control and line spectrum then reflect the noise level of different frequency and the relation of tested naval vessel diverse location by characteristic.The relation of some reference positions on measurement hydrophone and the hull is determined that on space (or time), measurement data and hull position have just formed one-to-one relationship so, and when it had reflected the naval vessel by measurement hydrophone, acoustic pressure was along the distribution of hull.By to vertically passing through specificity analysis, can obtain the corresponding relation at different frequency bands noise level and hull position, for the noise source position of determining the naval vessel provides a kind of method.Utilize the naval vessel to carry out the method that the vertical distribution character in ship noise source is measured by characteristic, test is simple but the noise source bearing accuracy is undesirable.

Shi Jie (time clean, Yang Desen, Shi Shengguo. the motion sound source based on the poorest performance optimization steadily and surely focuses on positioning identifying method research [J]. Acta Physica Sinica, 2011; 60 (6): 1-11.), Wang Zhiwei (Wang Zhiwei, Xu Lingji, Yang Yixin etc. line array identification underwater movement objective noise source method research [J]. vibration and impact, 2012; 31 (19): 118-122.) utilize the high resolution technique of sound focusing array to measure the noise source of underwater movement objective, bearing accuracy is higher.Yet for the low frequency spectrum lines sound source on the naval vessel, the array aperture that said method needs is too big, and to the shape need strictness that array lays, is difficult to be applied in the actual ship-radiated noise test.

Summary of the invention

In order to overcome the deficiencies in the prior art, the invention provides a kind of vertical distribution character measuring method of naval vessel line spectrum noise source that distributes based on Wigner-Ville, the Doppler shift characteristics of utilizing tested naval vessel and measurement hydrophone relative motion to bring only uses single nautical receiving set to realize measurement to the vertical distribution character of naval vessel line spectrum noise source.

The technical solution adopted for the present invention to solve the technical problems may further comprise the steps:

The first step, any fixed position L on the naval vessel _cThe place lays a synchronous orientator of the underwater sound as beacon source, and at the uniform velocity line navigation is done with speed v in the naval vessel, and the velocity of sound is c under water, and the distance abeam of measurement hydrophone and Ship Motion track is R ₀, the acoustical signal that measurement hydrophone receiving ship beam is penetrated, and convert thereof into voltage signal s (t), 0＜t≤T, T represent the time span of data recording;

Second step received signal s (t) to the nautical receiving set that collects earlier and does the fast fourier transform analysis spectrum, found the low frequency spectrum lines that exists in the signal, its frequency

M=1,2 ..., M, M represent the number of low frequency spectrum lines, isolate the frequency span that has line spectrum by bandpass filter to be Each zonule signal obtains each low frequency spectrum lines noise source Doppler signal s _m(t), m=1,2 ..., M; With s _m(t) plural numberization obtains Doppler's analytic signal z _m(t)=s _m(t)+jH[s _m(t)], H[s _m(t)] expression signal s _m(t) Hilbert transform;

In the 3rd step, the beam that obtains each low frequency spectrum lines noise source is estimated evaluation t ' constantly _M0After, by formula $\left\{\begin{array}{cc}0<t<{2t}_{m0}^{\&prime;}& t_{m0}^{\&prime;}\&le;T/2\\ {2t}_{m0}^{\&prime;}-T<t\&le;T& t_{m0}^{\&prime;}>T/2\end{array}\right.$ Intercepting z _m(t) obtain Doppler signal z ' to be analyzed _m(t); Then to the Doppler signal z ' after the intercepting _m(t) be WVD: $W_{z_m^{\&prime;}}(t,f)={\&Integral;}_{-\&infin;}^{\&infin;}{z}_m^{\&prime;}(t+\frac{\mathrm{\&tau;}}{2}){z_m^{\&prime;}}^{*}(t-\frac{\mathrm{\&tau;}}{2})e^{-j2\mathrm{\&pi;f\&tau;}}\mathrm{d\&tau;},$ Wherein t is the time, and f is frequency, and τ is time delay, and * represents conjugation, obtains the Doppler signal energy about the distribution of temporal frequency; Utilize the energy peak detection method

Obtain the beam moment estimated value when each low frequency spectrum lines noise source is by measurement hydrophone on the naval vessel

In the 4th step, the synchronous orientator of the underwater sound can obtain known location L _cBeam when beacon source is passed through measurement hydrophone is t constantly _C0With the Ship Motion speed v, utilize each noise source and beacon source by the measurement hydrophone beam mistiming constantly, in conjunction with the Ship Motion speed v, can determine each the noise source position that vertically distributes on the naval vessel

The invention has the beneficial effects as follows: measure on the platform of ship-radiated noise at existing single nautical receiving set, the Doppler effect that relative motion produces between naval vessel and the measurement hydrophone when utilizing measurement, in conjunction with the time frequency analysis signal processing technology, realize the measurement of the vertical distribution character of naval vessel low frequency spectrum lines noise source, this method is implemented simple, and measuring accuracy is than passing through characteristic method height.

Description of drawings

Fig. 1 is ship-radiated noise measurement model synoptic diagram;

Fig. 2 is the overall procedure block diagram of the vertical Distribution and localization method of naval vessel line spectrum noise source.

Embodiment

The present invention is fixed position L on the naval vessel _cThe place lays a synchronous orientator of the underwater sound as beacon source, and at the uniform velocity line navigation is done with speed v in the naval vessel, draws near also from the close-by examples to those far off to leave measurement hydrophone near measurement hydrophone, and the distance abeam of measurement hydrophone and Ship Motion track is R ₀, the acoustical signal that measurement hydrophone receiving ship beam is penetrated in this process, and convert thereof into voltage signal s (t), 0＜t≤T notes with data collecting instrument by preceding putting the back, and T represents the time span of data recording.

The receiving hydrophone signal demand pre-service of record, purpose is: the one, determine the line spectrum noise source signal that exists; The 2nd, the out-of-band noise of Doppler signal is removed in filtering; The 3rd, plural numberization obtains the Doppler signal of analytical form.Earlier the nautical receiving set that collects is received signal s (t) and do the fast Fourier transform (FFT) analysis spectrum, find the low frequency spectrum lines that exists in the signal, its frequency

M=1,2,, M, M represent the number of low frequency spectrum lines, i.e. low frequency spectrum lines noise source number to be analyzed.Isolating the frequency span that has line spectrum by bandpass filter is

Each zonule signal, this just obtains each low frequency spectrum lines noise source Doppler signal s _m(t), m=1,2,, M.With isolated line spectrum noise source Doppler signal s _m(t) plural numberization obtains Doppler's analytic signal z _m(t), z wherein _m(t)=s _m(t)+jH[s _m(t)], H[s _m(t)] expression signal s _m(t) Hilbert transform.

Because have relative motion between tested naval vessel and the measurement hydrophone, amplitude and the frequency of the line spectrum noise source signal that measurement hydrophone receives change, the variation of frequency is called Doppler shift.Doppler signal z _m(t) amplitude is

Represent each line spectrum noise source radiation intensity A _M0With the decay of spherical wave form, t _M0For each line spectrum noise source by the beam of beam position when nearest from measurement hydrophone constantly; Signal z _m(t) frequency is $f_m=\frac{f_{m0}{c}^2}{c^2-v^2}(1-\frac{v^2(t-t_{m0})}{\sqrt{{R_0}^2(c^2-v^2)+v^2{c}^2{(t-t_{m0})}^2}}),$ C is the velocity of sound in the water, f _M0The frequency of each radiant rays spectral noise source signal on the expression naval vessel.Doppler signal z _m(t) frequency change is non-linear, utilizes secondary Time-Frequency Analysis Method Wigner-Ville distribution (WVD) to analyze Doppler signal z _m(t) can occur disturbing from cross term, this instantaneous Frequency Estimation to signal is disadvantageous, but from the existence of cross term to estimating beam t constantly _M0Useful.Because Doppler signal WVD from the convolution effect of cross term at frequency domain, causes except t=t _M0Constantly, should accumulate in (t, f on the Doppler signal WVD time frequency plane _m) energy spread located.Utilize Doppler signal WVD from this character of cross term, directly Doppler signal being carried out WVD can be at time frequency plane (t _M0, f _M0) locate to form energy peak.In addition because of Doppler signal z _m(t) changes in amplitude causes the energy of signal at t _M0The time also maximum, Doppler signal WVD is at (t like this _M0, f _M0) energy peak located is more obvious.Beam when finding energy peak point position on Doppler's time frequency plane can obtain that each low frequency spectrum lines noise source is by measurement hydrophone on the naval vessel is t constantly _M0

In order to take full advantage of the energy spread effect from cross term of Doppler signal WVD, reply z _m(t) intercept, the principle of intercepting is that the analysis time of Doppler signal is as far as possible long and serve as the mid point of intercepting time period constantly with the beam of pre-estimation, and the beam of pre-estimation can adopt by methods such as characteristic methods and obtain constantly.Estimate evaluation t ' constantly obtaining each noise beam in a steady stream _M0After, by formula $\left\{\begin{array}{cc}0<t<{2t}_{m0}^{\&prime;}& t_{m0}^{\&prime;}\&le;T/2\\ {2t}_{m0}^{\&prime;}-T<t\&le;T& t_{m0}^{\&prime;}>T/2\end{array}\right.$ Intercepting z _m(t) obtain Doppler signal z ' to be analyzed _m(t).Then to the Doppler signal z ' after the intercepting _m(t) be WVD: $W_{z_m^{\&prime;}}(t,f)={\&Integral;}_{-\&infin;}^{\&infin;}{z}_m^{\&prime;}(t+\frac{\mathrm{\&tau;}}{2}){z_m^{\&prime;}}^{*}(t-\frac{\mathrm{\&tau;}}{2})e^{-j2\mathrm{\&pi;f\&tau;}}\mathrm{d\&tau;}$ Obtain the Doppler signal energy about the distribution of temporal frequency.WVD is the instantaneous autocorrelation function that utilizes signal

Do Fourier transform, algorithm generally is to realize by FFT.Because the movement velocity on tested naval vessel is slow, radiant rays spectral noise source frequency is positioned at low frequency, and Doppler frequency changes faint, thus FFT count to obtain very big, so just can be in frequency axis formation one trickle rule to observe small frequency change.Have at the time frequency analysis of low frequency spectrum lines Doppler signal that frequency band is narrow, the demanding characteristics of refinement, do not need to analyze Doppler shift frequency band data in addition, therefore use the Chirp-Z method of local frequencies refinement to replace FFT in the implementation algorithm, under the condition that guarantees the frequency discrimination precision, improved counting yield.Utilize the energy peak detection method at last Obtain the beam moment estimated value when each line spectrum noise source is by measurement hydrophone on the naval vessel

The synchronous orientator of the underwater sound can obtain known location L _cBeam when beacon source is passed through measurement hydrophone is t constantly _C0With the Ship Motion speed v, utilize each noise source and beacon source by the measurement hydrophone beam mistiming constantly, in conjunction with the Ship Motion speed v, according to formula

Can determine vertical each noise source position L that distributes on the naval vessel _m

The present invention is further described below in conjunction with drawings and Examples.

Fig. 1 is the measurement model of ship-radiated noise, and measurement hydrophone is positioned at the S place, tested naval vessel uniform motion, and speed is v, and track is MN, and beam position O is that its running orbit is from the nearest point of measurement hydrophone, fixed position L on the naval vessel _cThe place lays a synchronous orientator of the underwater sound as beacon, and the naval vessel passes through in the process of measurement hydrophone, the acoustical signal that measurement hydrophone receiving ship beam is penetrated, and convert thereof into voltage signal s (t), use data collecting instrument with sampling rate F by preposition amplification back _SWriting time, length was the data of T, obtained the discrete-time series s (n) of signal s (t), n=1 ..., N, N=TF _S

Fig. 2 is the overall procedure of the vertical Distribution and localization method of naval vessel line spectrum noise source, concrete enforcement is as follows: (1) receives Signal Pretreatment to nautical receiving set, earlier the signal s (n) that collects is done fast fourier transform (FFT) analysis spectrum, determine the low frequency spectrum lines that exists in the signal, its frequency

M=1,2 ..., M, M represent the number of low frequency spectrum lines, the low frequency spectrum lines noise source number that namely will analyze.Isolating the frequency span that has line spectrum by the FIR bandpass filter is

Each zonule signal obtains each line spectrum noise source Doppler signal s _m(n), m=1,2,, M.With isolated line spectrum noise source Doppler signal s _m(n) plural numberization obtains z _m(n), z wherein _m(n)=s _m(n)+jH[s _m(n)], H[s _m(n)] expression signal s _m(n) Hilbert transform.(2) to Doppler's analytic signal z of previous step _m(n) intercept, the principle of intercepting is that the analysis time of Doppler signal is as far as possible long and serve as the mid point of intercepting time period constantly with the beam of pre-estimation, utilizes can obtain beam by the characteristic method and estimate evaluation t ' constantly _M0, by formula $\left\{\begin{array}{cc}0<n\&le;{2t}_{m0}^{\&prime;}{F}_S& t_{m0}^{\&prime;}\&le;T/2\\ ({2t}_{m0}^{\&prime;}-T)F_S<n\&le;{\mathrm{TF}}_S& t_{m0}^{\&prime;}>T/2\end{array}\right.$ To sequence z _m(n) intercepting is always counted and is the Doppler signal time series z ' to be analyzed of N ' _m(n), n=1,2 ..., N '.Realize high-frequency resolving accuracy Doppler signal z ' fast in conjunction with refinement Frequency Estimation Chirp-Z algorithm _m(n) Wigner-Ville distributes (WVD): at first construct a N ' * N ' dimension matrix 0＜n≤N ' wherein, L≤l≤L, L=(N '-1)/2, N ' gets odd number; (n, l) each row carries out ring shift, makes up N ' * N ' reform matrix with matrix G $X(n,l)=\left\{\begin{array}{cc}G(n,l)G^{*}(n,-l)& 0\&le;l\&le;L-1\\ G(n,l-2L)G^{*}(n,-l+2L)& L\&le;l\&le;2L\end{array}\right.,$ Wherein * represents conjugation, matrix X (n, capable vector x l) _n(l) the expression Doppler signal is at n/F _SInstantaneous autocorrelation sequence constantly; Numerical frequency low frequency and high frequency thresholding f with FIR bandpass filter in step (1) pre-service _b, f _eAs the original frequency of refinement frequency spectrum with stop frequency, Δ f is the refinement frequency interval, the counting of refinement frequency

Structure frequency sampling factor z _k=AW ^-k, wherein $\left\{\begin{array}{c}A=e^{j4\mathrm{\&pi;}{f}_b}\\ W=e^{-j4\mathrm{\&pi;\&Delta;f}}\end{array}\right.;$ Structure length L ' unit response sequence $h\left(l\right)=\left\{\begin{array}{cc}{W}^{{-l}^2/2}& 0\&le;l\&le;K-1\\ 0& K\&le;l\&le;L^{\&prime;}-N^{\&prime;}\\ W^{-{(L-l)}^2/2}& L^{\&prime;}-N^{\&prime;}+1\&le;l\&le;L^{\&prime;}-1\end{array}\right.,$ L ' is near 2 the power of N '+K-1; To x _n(l) be weighted processing

0≤l≤N '-1 is at y ' _n(l) zero padding in the middle of the data obtains $y_n\left(l\right)=\left\{\begin{array}{cc}{y}_n^{\&prime;}\left(l\right)& 0\&le;l\&le;L-1\\ 0& L\&le;l\&le;L^{\&prime;}-L\\ y_n^{\&prime;}(l-L^{\&prime;}+N^{\&prime;})& L^{\&prime;}-L+1\&le;l\&le;L^{\&prime;}-1\end{array}\right.;$ Ask h (l), y respectively _n(l) Fourier transform $\left\{\begin{array}{c}H\left(k\right)=\mathrm{FFT}\left[h\left(l\right)\right]\\ Y_n\left(k\right)=\mathrm{FFT}\left[y_n\left(l\right)\right]\end{array}\right.,$ Multiply each other at frequency domain then, and obtain convolution results q by contrary FFT computing _n(l)=IFFT[Y _n(k) H (k); Preceding K point data output to output sequence at last is weighted 0≤k≤K-1, F _n(z _k) be n/F _SThe frequency spectrum sequence of correspondence is formed matrix W (n, z with the power spectrum sequence of each moment correspondence constantly _k), just can obtain signal z ' _m(n) energy is about the distribution of time and frequency

Detect by energy peak $({\hat{f}}_{m0},{\hat{t}}_{m0})=\underset{t,f}{\mathrm{ArgMax}}\left\{W_{z_m^{\&prime;}}(t,f)\right\}$ Find The maximal value time corresponding, beam estimated value constantly when namely each noise is in a steady stream by measurement hydrophone

(3) the synchronous orientator of the underwater sound can obtain known location L _cBeam when beacon source is passed through measurement hydrophone is t constantly _C0With the Ship Motion speed v, utilize each noise source and beacon source by the measurement hydrophone beam mistiming constantly, in conjunction with the Ship Motion speed v, according to formula

Can determine vertical each line spectrum noise source position L that distributes on the naval vessel _m

Claims (1)

1. the vertical distribution character measuring method of naval vessel line spectrum noise source is characterized in that comprising the steps:

The first step, any fixed position L on the naval vessel _cThe place lays a synchronous orientator of the underwater sound as beacon source, and at the uniform velocity line navigation is done with speed v in the naval vessel, and the velocity of sound is c under water, and the distance abeam of measurement hydrophone and Ship Motion track is R ₀, the acoustical signal that measurement hydrophone receiving ship beam is penetrated, and convert thereof into voltage signal s (t), 0＜t≤T, T represent the time span of data recording;

Second step received signal s (t) to the nautical receiving set that collects earlier and does the fast fourier transform analysis spectrum, found the low frequency spectrum lines that exists in the signal, its frequency

M=1,2 ..., M, M represent the number of low frequency spectrum lines, isolate the frequency span that has line spectrum by bandpass filter to be

Each zonule signal obtains each low frequency spectrum lines noise source Doppler signal s _m(t), m=1,2 ..., M; With s _m(t) plural numberization obtains Doppler's analytic signal z _m(t)=s _m(t)+jH[s _m(t)], H[s _m(t)] expression signal s _m(t) Hilbert transform;

In the 3rd step, the beam that obtains each low frequency spectrum lines noise source is estimated evaluation t ' constantly _M0After, by formula $\left\{\begin{array}{cc}0<t<{2t}_{m0}^{\&prime;}& t_{m0}^{\&prime;}\&le;T/2\\ {2t}_{m0}^{\&prime;}-T<t\&le;T& t_{m0}^{\&prime;}>T/2\end{array}\right.$ Intercepting z _m(t) obtain Doppler signal z ' to be analyzed _m(t); Then to the Doppler signal z ' after the intercepting _m(t) be WVD: $W_{z_m^{\&prime;}}(t,f)={\&Integral;}_{-\&infin;}^{\&infin;}{z}_m^{\&prime;}(t+\frac{\mathrm{\&tau;}}{2}){z_m^{\&prime;}}^{*}(t-\frac{\mathrm{\&tau;}}{2})e^{-j2\mathrm{\&pi;f\&tau;}}\mathrm{d\&tau;},$ Wherein t is the time, and f is frequency, and τ is time delay, and * represents conjugation, obtains the Doppler signal energy about the distribution of temporal frequency; Utilize the energy peak detection method

Obtain the beam moment estimated value when each low frequency spectrum lines noise source is by measurement hydrophone on the naval vessel

In the 4th step, the synchronous orientator of the underwater sound can obtain known location L _cBeam when beacon source is passed through measurement hydrophone is t constantly _C0With the Ship Motion speed v, utilize each noise source and beacon source by the measurement hydrophone beam mistiming constantly, in conjunction with the Ship Motion speed v, can determine each the noise source position that vertically distributes on the naval vessel

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