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共有20条相似文献,以下是第1-20项 搜索用时 109 毫秒

1.  Geoacoustic Inversion Based on a Vector Hydrophone Array  被引次数:1
   彭汉书 李风华《中国物理快报》,2007年第24卷第7期
   We propose a geoacoustic inversion scheme employing a vector hydrophone array based on the fact that vector hydrophone can provide more acoustic field information than traditional pressure hydrophones. Firstly, the transmission loss of particle velocities is discussed. Secondly, the sediment sound speed is acquired by a matchedfield processing (MFP) procedure, which is the optimization in combination of the pressure field and vertical particle velocity field. Finally, the bottom attenuation is estimated from the transmission loss difference between the vertical particle velocity and the pressure. The inversion method based on the vector hydrophone array mainly has two advantages: One is that the MFP method based on vector field can decrease the uncertain estimation of the sediment sound speed. The other is that the objective function based on the transmission loss difference has good sensitivity to the sediment attenuation and the inverted sediment attenuation is independent of source level. The validity of the inverted parameters is examined by comparison of the numerical results with the experimental data.    

2.  A hybrid scheme for geoacoustic inversion  
   ZHANG Xuelei  LI Zhenglin  HUANG Xiaodi《Chinese Journal of Acoustics》,2010年第2期
   A hybrid inversion scheme of geoacoustic parameters, which combines dispersion characteristics of normal modes with transmission loss, has been proposed based on the facts that different parameters have different effects on sound field. First, considering the dispersion characteristics of normal modes were sensitive to the density and the sound speed of seabottom, and not sensitive to the seabottom attenuation coefficient, the group time delays of different modes and different frequencies were acquired through adaptive optimal kernel time-frequency representation, then the group time delays were taken as the cost function, and using a global optimal algorithm, the seabottom density and the profile of seabottom sound speed were deduced. Successively, the validity of inversion results was evaluated by the a posteriori probability. Last, the attenuation coefficient of sediment is inverted using the transmission loss data recorded from the ship radiation noise. The validity of the total inversion results has been evaluated by making use of the matched field processing source localization.    

3.  Extraction of mode attenuation coefficient from low frequency reverberation signal  
   ZHANG Ronghan  LI Qi《Chinese Journal of Acoustics》,2013年第3期
   A method of extracting normal mode attenuation coefficient from low frequency reverberation signal has been proposed.Pseudo-inverse normal mode filtering method is implemented to get single mode reverberation field firstly.Based on the assumption of separability of modal back-scattering matrix,effective back-scattering matrix element can be calculated using single mode average reverberation intensity.Finally,mode attenuation coefficient is extracted by comparing effective back-scattering matrix elements at different ranges.The extracted mode attenuation coefficients are used to predict sound transmission loss at the same experiment area. Results show that the predicted transmission loss agrees well with the measured data.This method avoids the difficult of treating the coupling between bottom scattering attenuation and normal mode propagation attenuation.Research on extraction of mode attenuation coefficient from low frequency reverberation signal is useful for both geoacoustic inversion and rapid underwater environment assessment.    

4.  Inversion for Sound Speed Profile by Using a Bottom Mounted Horizontal Line Array in Shallow Water  
   李风华  张仁和《中国物理快报》,2010年第27卷第8期
   Ocean acoustic tomography is an appealing technique for remote monitoring of the ocean environment. In shallow water, matched field processing (MFP) with a vertical line array is one of the widely used methods for inverting the sound speed profile (SSP) of water column. The approach adopted is to invert the SSP with a bottom mounted horizontal line array (HLA) based on MFP. Empirical orthonormal functions are used to express the SSP, and perturbation theory is used in the forward sound field calculation. This inversion method is applied to the data measured in a shallow water acoustic experiment performed in 2003, Successful results show that the bottom mounted HLA is able to estimate the SSP. One of the most important advantages of the inversion method with bottom mounted HLA is that the bottom mounted HLA can keep a stable array shape and is safe in a relatively long period.    

5.  Statistical geoacoustic inversion from vertical correlation of shallow water reverberation  被引次数:1
   GAO Wei  WANG Ning  WANG Haozhong《Chinese Journal of Acoustics》,2008年第27卷第4期
   Statistical geoacoustic inversion results based on reverberation vertical correlation (RVC) data from 300 Hz to 800 Hz are presented. The data were obtained during Yellow Sea Experiment-2005 (YSE-05). An uncertainty analysis is carried out. It is found that the inversion sea bottom sound velocities decrease when the frequency increases. So it is difficult to determine the sea bottom sound velocity. In order to solve this problem, a two-layer bottom model is assumed, and a multi-frequency inversion approach based on Genetic Algorithm is proposed. The approach is demonstrated using YSE-05 experiment data. Both RVC and normal modes depth functions (NMDFs) calculated using the inverted geoacoustic parameters are in good agreement with the experimental measurements.    

6.  Geoacoustic inversion based on reflection model of effective density fluid approximation  
   YU Shengqi HUANG Yiwang WU Qiong《Chinese Journal of Acoustics》,2014年第3期
   In order to obtain the physical and geoacoustic properties of marine sediments,an inverse method using reflection loss of different grazing angles is presented.The reflection loss is calculated according to the reflection model of effective density fluid approximation.A two-step hybrid optimization algorithm combining differential evolution and particle swarm optimization along with Bayesian inversion is employed in estimation of porosity,mean grain size,mass density and bulk modulus of grains.Based on the above physical parameters,geoacoustic parameters,including sound speed and attenuation,are further calculated.According to the numerical simulations,we can draw a conclusion that all the parameters can be well estimated with the exception of bulk modulus of grains.In particular,this indirect inverse method for bottom geoacoustic parameters performs high accuracy and strong robustness.The relative errors are 0.092%and 17%,respectively.Finally,measured reflection loss data of sandy sediments at the bottom of a water tank is analyzed,and the estimation value,uncertainty and correlation of each parameter are presented.The availability of this inverse method is verified through comparison between inverse results and part of measured parameters.    

7.  Inversion for the sea bottom acoustic parameters by using the group time delays and amplitude of normal mode  
   《Chinese Journal of Acoustics》,2003年第2期
   The group time delays and amplitudes of the normal mode are derived using the normal mode filter. The sea bottom sound speed, density and attenuation are inversely deduced by matching the group time delays and the amplitude of the normal mode. A genetic algorithm (GA) is used for optimization search in the parameter space. The inverted attenuation has the nonlinear frequency relationship a = 0.29f1.91 dB/m (the unit of frequency is kHz) in the frequency range 200 - 500 Hz. The theoretical transmission loss calculated using the deduced parameters matches the experiment data very well.    

8.  Sound speed profile inversion using a horizontal line array in shallow water  
   LI ZhengLin  HE Li  ZHANG RenHe  LI FengHua  YU YanXin  LIN Peng《中国科学:物理学 力学 天文学(英文版)》,2015年第1期
   It is better to use a simple configuration to enhance the applicability of ocean environment inversion in shallow water.A matched-field inversion method based on a horizontal line array(HLA)is used to retrieve the variation of sound speed profile.The performance of the inversion method is verified in the South China Sea in June,2010.An HLA laid at bottom was used to receive signals from a bottom-mounted transducer.Inverted mean sound speed profiles from 9-hour long acoustic signals are in good agreement with measurements from two temperature chains at the sites of the source and receiver.The results show that an HLA can be used to monitor the variability of shallow-water sound speed profile.    

9.  Time-Domain Geoacoustic Inversion Based on Normal Incidence Reflection from Layered Sediment  
   郭永刚 李风华 刘建军 李整林《中国物理快报》,2006年第23卷第9期
   We present a new geoacoustic inversion approach based on the stable inversion ot sediment acoustic impeaance from normal incident reflection data. The Hamilton empirical formulae are utilized to separate the impedance into velocity and density. The inverted results are evaluated by the measurement on the core samples. The predicted transmission losses (TLs) using the inverted results are in good agreement with the measured TLs from the explosive sources.    

10.  Multi-step geoacoustic inversion with a towed line array  
   《Chinese Journal of Acoustics》,2012年第2期
   Geoacoustic inversion is important for acoustic field predictions and matched field localizations in shallow water.Combing the Matched-field inversion(MFI) and the Reflectionloss inversion,a multi-step Bayesian inversion for geoacoustic parameters was presented.This method applied the posterior probability density(PPD) or inversion results from one inversion as prior information for subsequent inversion.First,the sensitive parameters were determined by the MFI.Second,the insensitive parameters were determined by the Reflection-loss inversion based on the PPD and inversion results from the MFI.The PPD results indicated that the multi-step inversion method was performed better than direct matched-field inversion,and the inversion results of some parameters were improved significantly.To demonstrate the advantages of the multi-step inversion method on the sound field prediction,the statistical properties of transmission loss based on the posterior probability were introduced.The transmission loss distribution showed that the predicted acoustic fields based on the multi-step inversion method had smaller errors.    

11.  Acoustic radiation analysis and experimental verification of a broadband dense plane array  
   LIU Wangsheng LI Ya'an YU Hongpei《Chinese Journal of Acoustics》,2011年第4期
   The sound field distribution of a broadband array is calculated using the acoustics FEM and BEM.The FEM-BEM model is established for a nine-element plane array and its numerical method of calculating mutual radiation impedance among the transducers is given. The changing law of mutual radiation impedance influencing acoustics performances is analyzed. The directivity and beam width of the plane array are calculated at three resonance frequencies.A broadband dense plane array with nine elements is developed using triply resonant transducers.The input impedance and directivity of the plane array are measured in anechoic water tank.Results show that it is reasonable to design the array according to the half wavelengh of the first resonance frequency of the array element.The numerical solution agrees with the measuring results well,which indicates the FEM-BEM method is feasible to calculate sound field distribution and analyze mutual impedances.    

12.  The nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores  
   冯雨霖  刘晓宙  刘杰惠  马力《中国物理 B》,2009年第18卷第9期
   Based on an equivalent medium approach,this paper presents a model describing the nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores.The influences of pores’ nonlinear oscillations on sound attenuation,sound dispersion and an equivalent acoustic nonlinearity parameter are discussed.The calculated results show that the attenuation increases with an increasing volume fraction of micropores.The peak of sound velocity and attenuation occurs at the resonant frequency of the micropores while the peak of the equivalent acoustic nonlinearity parameter occurs at the half of the resonant frequency of the micropores.Furthermore,multiple scattering has been taken into account,which leads to a modification to the effective wave number in the equivalent medium approach.We find that these linear and nonlinear acoustic parameters need to be corrected when the volume fraction of micropores is larger than 0.1%.    

13.  Characterization of electro-acoustics impedance and its application to active noise control  
   HOUHong YANGJianhua《Chinese Journal of Acoustics》,2004年第23卷第2期
   Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to Active Noise Control is demonstrated through a coil driven loudspeaker. A general formula of radiation impedance is derived for two control strategies, according to the criterion of total acoustic power output. The radiation impedances of some commonly used sound sources are calculated. We discuss in detail the relation between variation of the input electrical impedance and radiation impedance for the two control strategies. The measured data of the input electrical impedance from a loudspeaker agree fairly well with theoretical analysis. An AC- bridge circuit is designed in order to measure the weak variation of electrical impedance resulted from radiation impedance. The bridge relative output is unique for a certain control strategy, from which an impedance-based error criterion is then proposed and the implementation of its application to an active control system is analyzed. Numerical results of such criterion are presented. An analogue control system is set up and experiments are carried out in a semi-anechoic chamber to verify the new control approach.    

14.  A NEW FINITE DIFFERENCE METHOD FOR COMPUTING SOUND FIELD IN LINED DUCTS  
   朱之墀  王治国《Chinese Journal of Acoustics》,1988年第1期
   This paper presents a new finite difference method to calculate problems of sound propagation in linedducts.The MacCormack time-split explicit scheme has been used to solve the basic equations for determiningthe acoustic pressure and velocity.The problems of sound propagation in 3-D rectangular ducts have beensolved successfully by use of this scheme with the making of an approach to the acoustic boundary conditions.The finite difference schemes for full grid points and the stability condition of the method are also given in thepaper.This new method needs less storage and is more stable.Moreover,it is easier to program and debug,and,especially,is suitable for computing 3-D sound field.    

15.  IDENTIFICATION OF ELASTIC-PLASTIC MECHANICAL PROPERTIES FOR BIMETALLIC SHEETS BY HYBRID-INVERSE APPROACH  
   Honglei Zhang Xuehui Lin Yanqun Wang Qian Zhang Yilan Kang《Acta Mechanica Solida Sinica》,2010年第23卷第1期
   Analysis, evaluation and interpretation of measured signals become important components in engineering research and practice, especially for material characteristic parameters which can not be obtained directly by experimental measurements. The present paper proposes a hybrid-inverse analysis method for the identification of the nonlinear material parameters of any individual component from the mechanical responses of a global composite. The method couples experimental approach, numerical simulation with inverse search method. The experimental approach is used to provide basic data. Then parameter identification and numerical simulation are utilized to identify elasto-plastic material properties by the experimental data obtained and inverse searching algorithm. A numerical example of a stainless steel clad copper sheet is consid- ered to verify and show the applicability of the proposed hybrid-inverse method. In this example, a set of material parameters in an elasto-plastic constitutive model have been identified by using the obtained experimental data.    

16.  A Method of Measuring the In Situ Seafloor Sound Speed using Two Receivers with WarDing Transformation  
   李风华  张波  郭永刚《中国物理快报》,2014年第2期
   We present a method of measuring the in situ superficial seafloor sound speed by using two receivers deployed vertically in sediment, based on the dispersion characteristic of normal modes in shallow water. Warping transfor- mation is adopted to extract the first normal mode from the broadband propagation signals. Some experimental results which could validate the method are shown. One of the advantages of the method is that the seafloor sound speed can be solved directly from the relative vertical transmission loss of the first normal mode without the exact priori information of the environmental parameters such as the sound speed profile, the water-column depth and the source location.    

17.  Design of sandwich acoustic window for sonar domes  
   YUMengsa LIDongsheng GONGLi XUJian《Chinese Journal of Acoustics》,2005年第24卷第2期
   Aimed at the low noise design of sonar dome in ships, a method has been presented for calculating the sonar self noise of a simplified sonar dome consisting of sandwich acoustic window and parallel acoustic cavity, which is excited by stationary random pressure fluctuation of turbulence boundary layer, using temporal and spatial double Fourier transform and wavenumber-frequency spectrum analysis. After numerically analyzing the influence of geometrical and physical parameters of acoustic window on the sonar self noise, the design method and reasonable parameters for sandwich acoustic window are proposed. The results show that the property of low noise induced by acoustic window of sandwich is dominated by the cut-off effect of longitudinal wave and transverse wave propagating in the visco-elastic layer of sandwich as well as the mismatch effect of impedance. If the thickness, density, Young‘s modulus and damping factor of plates and visco-elastic layer as well as the sound speed of longitudinal wave and transverse wave in the visco-elastic layer are selected reasonably, the maximum noise reduction of sandwich acoustic window is 6.5 dB greater than that of a single glass fiber reinforced plastic plate.    

18.  A study on the multi-freedom broadband impedance model for time-domain simulations  
   LI Xiaodong  LI Xiaoyan《Chinese Journal of Acoustics》,2012年第3期
   The purpose of this paper is to construct a general broadband impedance model, which is suited for predicting acoustic propagation problems in time domain.A multi-freedom broadband impedance model for sound propagation over impedance surfaces is proposed and the corresponding time domain impedance boundary condition is presented.Basing on the extended Helmholtz resonator,the multi-freedom impedance model is constructed through combing with a sum of rational functions in the form of general complex-conjugate pole-residue pairs and it is proved that the impedance model is well posed.The impedance boundary condition can be implemented into a computational aeroacoustics solver by a recursive convolution technique, which results in a fast and computationally efficient algorithm.The two dimensional and three dimensional benchmark problems are selected to validate the accuracy of the proposed impedance model and time domain simulations.The numerical results are in good agreement with the reference solutions.It is demonstrated that the proposed impedance model can be used to describe the broadband characteristics of acoustic liners,and the corresponding time domain impedance boundary condition is viable and accurate for the prediction of sound propagation over broadband impedance surfaces.    

19.  AN INVERSION METHOD FOR OBTAINING BOTTOM REFLECTION LOSS  
   《Chinese Journal of Acoustics》,1989年第1期
   A method for the inversion of the transmission losses for the bottom reflection loss is proposed on thebasis of the theory of the smooth-averaged sound field.The procedure of the inversion is based on the cri-terion of the least square error in the transmission losses between calculation and measurement.By using theGauss-Newton iterative approach,the non-linear least square aloqrithm is equivalent to solving a se-quence of lineared least square problems.The physical causes of the instability of the invertion problem arediscussed and the stability is improved by means of the Levenberg-Marquardt method.Both numericalsimulations with noise and experimental results show that the inversion for the bottom reflection loss ofsmall grazing angle has high precision and the certain perturbation in the measured transmission losses doesnot lead to serious deviation in the inversion result of the bottom reflection loss.    

20.  Acoustic performance prediction of Helmholtz resonator with conical neck  
   LIU Haitao  ZHENG Sifa  LIAN Xiaomin  DAN Jiabi《Chinese Journal of Acoustics》,2014年第4期
   There is no accurate analytical approach for the acoustic performance prediction of Helmholtz resonator with conical neck,which has broad band acoustic attenuation performance in the low frequency range.To predict the acoustic performance of the resonator accurately,a general theory model based on the one-dimensional analysis approach with acoustic length corrections is developed.The segmentation method is used to calculate the acoustic parameters for sound propagation in conical tubes.And then,an approximate formula is deduced to give accurate correction lengths for conical tubes with difierent geometries.The deviations of the resonance frequency between the transmission loss results obtained by the general theory with acoustic lengths correction and the results from the finite element method and experiments are less than 2 Hz,which is much better than the results from one-dimensional approach without corrections.The results show that the method of acoustic length correction for the conical neck greatly improved the accuracy of the one-dimensional analysis approach,and it will be quick and accurate to predict the sound attenuation property of Helmholtz resonator with conical neck.    

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