CN105631194B - A kind of method using mode dispersion curve energy difference Inversion for bottom attenuation coefficient - Google Patents
A kind of method using mode dispersion curve energy difference Inversion for bottom attenuation coefficient Download PDFInfo
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Abstract
The present invention relates to a kind of method using mode dispersion curve energy difference Inversion for bottom attenuation coefficient, utilize the amplitude energy information of mode dispersion curve, realize the inverting to seabed attenuation coefficient, the present invention propose it is a kind of using two explosive bomb mode dispersion curve energy differences come the method for Inversion for bottom attenuation coefficient, the seabed attenuation coefficient in experiment sea area is estimated for realizing.The inventive method make use of broadband explosive sound source propagated in shallow sea caused by frequency dispersion effect, emphasis inverting shallow sea area.Receiving hydrophone cloth is placed on certain depth by the inventive method first, then the explosive sound source of model parameter identical (thinking that explosion time produces identical signal) is launched in same straight line, different distance, so as to receive the time-frequency figure of two explosive sound sources；Then converted using warping and the time-frequency figure of two explosive sound sources is handled, it is poor so as to obtain the transmission energy of preceding 4 rank mode dispersion curve；Then mode dispersion curve energy difference Inversion for bottom attenuation coefficient is utilized.
Description
Technical Field
The invention belongs to an inversion method of a submarine attenuation coefficient, in particular relates to a method for inverting the submarine attenuation coefficient by using modal dispersion curve energy difference, is suitable for shallow sea areas with stable horizontal variation, and belongs to the field of underwater acoustics and underwater acoustic signal processing.
Background
The method is mainly used for inversion of shallow sea bottom attenuation coefficients. In underwater acoustics, the attenuation coefficient of the sea bottom is an important factor influencing the propagation of underwater acoustic signals, and directly influences the performance parameters of sonar equipment. When a broadband signal propagates in shallow sea, dispersion effects occur. According to the normal wave theory, although the dispersion effect increases the processing difficulty of the underwater acoustic signals, the dispersion effect also carries relevant information of marine environmental parameters, and compared with the traditional direct sampling, the inversion method has the advantages of low cost, high speed, easiness in implementation and the like. Therefore, the inversion of marine environmental parameters by using modal dispersion curves gradually becomes a hot point problem in water acoustics.
At present, the method for inverting the parameters of the seabed sediment by using the normal wave group delay of a single explosive sound source can be referred to as Geoactive inversion in a dispersion wave using the scanning operators, which is published in the Journal of the scientific Society of America at the 130 th stage in 2011, and the starting page number is EL101. The method for extracting parameters such as the seabed sound velocity and the like by utilizing the Wigner-Ville distribution and the normal wave group delay inversion can be referred to as a combined inversion method of the earth sound parameters, which is published in 2009 in the 1 st stage of acoustical science and newspaper, and the initial page number is 54. However, the above methods invert the marine environment parameters under the condition of a single hydrophone and a single sound source, only utilize the time delay information of a broadband sound source frequency dispersion curve, do not fully utilize the amplitude energy information of a modal frequency dispersion curve, and do not invert the submarine attenuation coefficient through the modal frequency dispersion energy.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a method for inverting the sea floor attenuation coefficient by using modal dispersion curve energy difference.
Technical scheme
A method for inverting a sea floor attenuation coefficient by using modal dispersion curve energy difference is characterized by comprising the following steps:
step 1: two distances r are respectively put at the same depth of the measured seabed area 1 And r 2 The explosive sound source, the hydrophone distribution point and the two explosive sound sources are on the same straight line, and the first 4-order modal dispersion curves of the two explosive sound sources are respectively extracted, and the method comprises the following steps:
step (1 a): the two distances received by the hydrophone are respectively r 1 And r 2 The two time domain signals of the explosive sound source are represented by the first 4 th order modal dispersion curve as follows:
in the formula A m (t) is the instantaneous amplitude of the mth order mode, f cm = mc/2D represents the cut-off frequency of the mth order mode, D is the average water depth of the experimental sea area, and c is the average sound velocity in water;
step (2 a): using waring transformation function h i (t)＝[t 2 +(r i /c) 2 ] 1/2 I = two received by 1,2 pairs of hydrophonesThe time domain receiving signals of the explosive sound source are respectively transformed, and two receiving signals of a warping domain are obtained:
in the formula h i ' (t) denotes warping transformation function h i (t) a derivative of;
step (3 a): and respectively filtering two received signals of the warping domain to separate the first 4-order modes. The filtering bandwidth settings are the same as: the 1 st order frequency band is 0-6Hz, the 2 nd order frequency band is 7-13Hz, the 3 rd order frequency band is 14-19Hz, and the 4 th order frequency band is 20-25Hz; thereby separating the first 4-order modal dispersion curves of the two received signals of the waring domain;
step (4 a): using inverse warping transform functionsi =1,2, respectively processing the first 4-order modal dispersion curves of the two received signals in the warping domain after the filtering processing, thereby separating the first 4-order modal dispersion curves of the two received signals in the original time domain;
and 2, step: inverting the sea bottom attenuation coefficient by the modal dispersion curve energy difference, and comprising the following steps of:
step (1 b): performing modal amplitude ratio on the dispersion curves with the same order in the separated first 4-order modal dispersion curves of the two original time domain received signals to obtain an mth-order modal amplitude ratio with the corresponding frequency f as follows:
in which E {. Cndot } represents the mean value, t o A time coordinate representing a point on the modal dispersion curve corresponding to a frequency f, for f ≦ 100Hz: Δ t =0.1s, Δ f =2Hz; for f>100 Hz：Δt＝0.02 s，Δf＝10Hz。Andrespectively representing the m-th order modal amplitude of the two explosion sound sources with the corresponding frequency f;
step (2 b): by setting the sea bottom attenuation coefficient beta at [00.5 ]]Change within range to make cost functionWhen the minimum value is obtained, the corresponding beta value is the seabed attenuation coefficient value obtained by inversion;
inverted cost functionComprises the following steps:
in the formulaRepresenting the modal amplitude ratio obtained from experimental data,a modal amplitude ratio calculated for the model;andrespectively a lower sideband and an upper sideband corresponding to the mth order mode, and during calculation, the lower sideband and the upper sideband are set to be
Advantageous effects
The invention provides a method for inverting a seabed attenuation coefficient by using modal dispersion curve energy difference, which fully utilizes amplitude energy information of a modal dispersion curve to realize inversion of the seabed attenuation coefficient. The method of the invention utilizes the frequency dispersion effect generated when the broadband explosive sound source is propagated in the shallow sea, and the shallow sea area is inverted in a key way. Firstly, laying receiving hydrophones at a certain depth, then putting explosion sound sources with the same model parameters (the same signals are generated during explosion) on the same straight line and different distances, and receiving time-frequency graphs of the two explosion sound sources; then, processing the time-frequency graphs of the two explosion sound sources by warping conversion, thereby obtaining the transmission energy difference of the first 4-order modal dispersion curves; and then inverting the sea floor attenuation coefficient by using the modal dispersion curve energy difference.
The beneficial effects are as follows: firstly, the signals of two explosion sound sources which are arranged on a straight line and have different distances and received by a single hydrophone arranged at a certain depth are utilized, then a first 4-order modal dispersion curve in a received signal time-frequency graph is extracted by warping conversion, and finally the energy difference of the modal dispersion curve is utilized to invert the sea bottom attenuation coefficient. The core idea of the invention is to extract modal dispersion curve energy of two explosive sound sources with different distances on the same straight line, and further to perform inversion of the sea bottom attenuation coefficient by using modal energy difference of different frequencies. The shallow sea bottom attenuation coefficient has great influence on the propagation of the sound signal, and the accurate sea bottom attenuation coefficient value is difficult to obtain by sea bottom sampling, so the method realizes the accurate estimation of the sea bottom attenuation coefficient, and lays a solid foundation for offshore battles
Drawings
FIG. 1 is a shallow sea environment model used in the method of the present invention
FIG. 2 is a shallow sea sound velocity profile used in the method of the present invention.
Fig. 3 is a time series of explosive sources received at close range by the method of the present invention.
FIG. 4 is a time domain waveform and a time-frequency diagram of an explosive sound source received at two different distances by the method of the present invention.
Fig. 5 shows modal dispersion energy of two explosive sources extracted by the method of the present invention.
FIG. 6 is a variation curve of the sea bottom attenuation coefficient obtained by the method of the present invention and inverted by using sound sources at different distances.
Detailed Description
The invention will now be further described with reference to the following examples, and the accompanying drawings:
referring to fig. 1 and 2, the submarine attenuation coefficient is inverted by a system consisting of 2 explosive sound sources with a detonation depth of 50m and 1 hydrophone, and the channel environment is shallow sea with a sea depth of about 105m, a sound source depth of 50m and a receiving depth of 48m. The receiving hydrophone is 49.6km away from the first explosion sound source and 63.4km away from the second explosion sound source; the thickness of the sedimentary layer is 13.9m, the sound velocity of the sedimentary layer is 1578.6m/s, and the density of the sedimentary layer is 1.6g/cm 3 The sound velocity of the basal layer is 1716.2m/s, and the density of the basal layer is 2.18g/cm 3 (ii) a The shallow sea acoustic velocity profile is the acoustic velocity profile shown in FIG. 2.
Referring to fig. 4 and 5, it can be seen that the first 4-order modes of the two explosive sound sources received by the hydrophone are separated in the low frequency band, and exhibit a dispersion characteristic, so that the first 4-order mode dispersion curves of the two explosive sound sources in the low frequency band (f <300 Hz) are extracted by using warping transform. The white curve in fig. 5 is the extracted modal dispersion curve. The method comprises the following steps:
(1) the two distances received by the hydrophone are r respectively 1 And r 2 The two time domain signals of the explosive sound source are represented by the first 4 th order modal dispersion curve as:
in the formula A m (t) is the instantaneous amplitude of the mth order mode, f cm = mc/2D represents the cutoff frequency of the mth order mode, D is the average water depth of the experimental sea zone, and c is the average sound velocity in water.
(2) Using warping transformation function hi (t) = [ t ] 2 +(r i /c) 2 ] 1/2 I =1,2 respectively transforms the time domain received signals of the two explosive sound sources received by the hydrophone, and obtains two received signals of a warping domain as follows:
in the formula h i ' (t) denotes warping transformation function h i (t) derivative of (t).
(3) And (4) respectively filtering two received signals of the warping domain to separate the first 4-order modes. The filtering bandwidth settings are the same as: the 1 st order band is 0-6Hz, the 2 nd order band is 7-13Hz, the 3 rd order band is 14-19Hz, and the 4 th order band is 20-25Hz. Thereby separating the first 4 order modal dispersion curves of the two received signals of the waring domain.
(4) Using inverse warping transform functionsi =1,2, respectively processing the first 4-order modal dispersion curves of the two received signals in the warping domain after the filtering processing, thereby separating and extracting the first 4-order modal dispersion curves of the two received signals in the original time domain.
(1) Referring to fig. 3 and 5, the seafloor attenuation coefficients are inverted by modal dispersion curve energy differences. The specific method comprises the following steps:
(1) performing modal amplitude ratio on the dispersion curves with the same order in the separated first 4-order modal dispersion curves of the two original time domain received signals to obtain an mth-order modal amplitude ratio with the corresponding frequency f as follows:
in which E {. Cndot } represents the mean value, t o A time coordinate representing a point on the modal dispersion curve corresponding to a frequency f, for f ≦ 100Hz: Δ t =0.1s, Δ f =2Hz; for f>100 Hz：Δt＝0.02 s，Δf＝10Hz。Andrespectively representing the m-th order modal amplitudes of the two explosive sound sources with corresponding frequencies f. In fig. 5, taking 50Hz and 150Hz as examples, the black rectangular frame in fig. 5 is the region of modal energy required to be calculated corresponding to 50Hz, and the red rectangular frame is the region of modal energy required to be calculated corresponding to 150 Hz.
(2) By setting the sea bottom attenuation coefficient beta at [00.5]Change within range to make cost functionAnd when the minimum value is obtained, the corresponding beta value is the seabed attenuation coefficient value obtained by inversion. Inverted cost functionComprises the following steps:
in the formulaRepresenting the modal amplitude ratio obtained from experimental data,modal amplitude ratios calculated for the model.Andrespectively a lower sideband and an upper sideband corresponding to the mth order mode, and during calculation, the lower sideband and the upper sideband are set to be
(3) In order to obtain the modal amplitude of the simulated explosive sound source, the invention uses the time series of the explosive sound source received in a very close distance as the simulated transmitting sound source, which is shown in fig. 3. And the simulated receiving signals at the corresponding distance are obtained through calculation of a Kraken model, so that the initial time of the simulated transmitting signals is almost the same as the initial time of the actual explosion signals.
Referring to fig. 6, the seafloor attenuation coefficients at different receive depths are calculated by placing the receiving hydrophones at 27.4m, 48.3m and 67.2m depths over one distance. And calculating the sea bottom attenuation coefficients at different distances by continuously changing the distance between the two explosive sound sources. Wherein the distance shown on the abscissa of fig. 6 is the average distance of two explosive sound sources. The dashed line in fig. 6 indicates that the calculated average seafloor attenuation coefficient is 0.0912dB/λ.
Claims (1)
1. A method for inverting a submarine attenuation coefficient by using modal dispersion curve energy difference is characterized by comprising the following steps:
step 1: two distances r are respectively put at the same depth of the measured seabed area 1 And r 2 The explosive sound source, the hydrophone distribution point and the two explosive sound sources are on the same straight line, and the first 4-order modal dispersion curves of the two explosive sound sources are respectively extracted, and the method comprises the following steps:
step (1 a): the two distances received by the hydrophone are r respectively 1 And r 2 The two time domain signals of the explosive sound source are represented by the first 4 th order modal dispersion curve as follows:
in the formula A m (t) is the instantaneous amplitude of the mth order mode, f cm = mc/2D represents the cut-off frequency of the mth order mode, D is the average water depth of the experimental sea area, and c is the average sound velocity in water;
step (2 a): using warping transform function h i (t)＝[t 2 +(r i /c) 2 ] 1/2 I =1,2 respectively transforms the time domain received signals of the two explosive sound sources received by the hydrophone, and obtains two received signals of a warping domain as follows:
in the formula h i ' (t) denotes warping transformation function h i (t) derivative of;
step (3 a): respectively filtering two received signals of a warping domain to separate the first 4-order modes; the filtering bandwidth settings are the same as: the 1 st order frequency band is 0-6Hz, the 2 nd order frequency band is 7-13Hz, the 3 rd order frequency band is 14-19Hz, and the 4 th order frequency band is 20-25Hz; thereby separating the first 4-order modal dispersion curves of the two received signals of the waring domain;
step (4 a): using inverse warping transform functionsi =1,2, respectively processing the first 4-order modal dispersion curves of the two received signals in the warping domain after the filtering processing, thereby separating the first 4-order modal dispersion curves of the two received signals in the original time domain;
and 2, step: inverting the sea floor attenuation coefficient by the energy difference of the modal dispersion curve, comprising the following steps:
step (1 b): carrying out modal amplitude ratio on the dispersion curves with the same order in the separated first 4-order modal dispersion curves of the two original time domain received signals to obtain an mth-order modal amplitude ratio with the corresponding frequency f as follows:
where E {. Cndot } represents the mean, to represents the time coordinate of the point corresponding to frequency f on the modal dispersion curve, for f ≦ 100Hz: Δ t =0.1s, Δ f =2Hz; for f>100Hz：Δt＝0.02s，Δf＝10Hz；Andrespectively representing the m-th order modal amplitude of the two explosion sound sources with the corresponding frequency f;
step (2 b): by setting the sea bottom attenuation coefficient beta at [00.5]Change within range to make cost functionWhen the minimum value is obtained, the corresponding beta value is the seabed attenuation coefficient value obtained by inversion;
inverted cost functionComprises the following steps:
in the formulaRepresenting the modal amplitude ratio obtained from experimental data,modal amplitude ratio calculated for the model;andrespectively a lower sideband and an upper sideband corresponding to the mth order mode, and during calculation, the lower sideband and the upper sideband are set to be
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| CN109443516B (en) * | 2018-12-25 | 2020-07-14 | 西北工业大学 | Seabed sound velocity passive acquisition method based on noise field vertical vibration velocity signal |
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| CN111563233B (en) * | 2020-04-12 | 2023-03-24 | 西北工业大学 | Passive inversion method for frequency dispersion characteristics of underwater acoustic signals based on nonlinear Bayesian theory |
| CN112346038B (en) * | 2020-10-21 | 2022-07-19 | 自然资源部第三海洋研究所 | Sound channel response estimation method based on shallow sea explosion sound propagation signal |
| CN113532629B (en) * | 2021-06-24 | 2024-04-12 | 中国人民解放军96901部队26分队 | Explosion sound source energy estimation method based on ray tracing |
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