Bayesian Tracking in an Uncertain Shallow Water Environment

A Bayesian source tracking approach is developed to track a moving acoustic source in an uncertain ocean environment.This approach treats the environmental parameters(e.g.,water depth,sediment and bottom parameters) at the source location and the source parameters(e.g.,source depth,range and speed) as unknown random variables that evolve as the source moves.To track a target with low signal-to-noise ratio(SNR),acoustic signals from a series of observations are treated in a simultaneous inversion.This allows real-time updating of the environment and accurate tracking of the moving source.The noise signals radiated from a surface ship target are processed and analyzed.It is found that the Bayesian source tracking method could enhance the localization accuracy in an uncertain water environment and low SNR.     

Video visualization for moving sound sources based on binoculars stereo and acoustic holography

The video visualization methods for moving sound sources are very important. The spatial positions in the sound filed measurement of moving sources arc measured by an automated method based on the binoculars stereo technique,the spatial coordinates of the surface of the moving sound source are determined automatically.The sound field of the surface of the moving source is reconstructed with a microphone array using the acoustic holography method for moving sound sources.The spatial mapping between the sound field and the video images is constructed,and also the time sequence of the sound field and the images is founded. Then,the reconstructed sound field and the real-world images are merged,and the visualized sound field video of the moving source is generated automatically.A sound field measurement system based on this method is developed,the measurement results of the moving sound source with this system indicate that the sound field video visualization is realized effectively with the proposed method,the sound sources and their changing process can be seen directly from the generated video,the identification and localization for the moving sound sources can be easier with this method.     

基于声全息方法和双目视觉实现运动声源声场可视化

运动声源声场的可视化是一种重要的运动声源定位的技术手段,利用双目视觉测量技术实现运动声源声场空间的自动测量,自动确定运动声源表面的空间位置,针对声源表面,利用传声器阵列,基于声全息方法实现运动声源声场的重建,建立视频图像与声场的空间映射,并建立视频与声场之间的时序,实现实景视频图像与声场重建结果的融合,可以自动生成声源运动过程的视频。基于该方法所开发了一套试验测量系统,对运动声源的测量试验结果表明,该方法可以有效实现运动声源的视频可视化,使人可以直接从视频中看到声源及其变化过程,使声源的定位和识别变得更加简单。      

非自由声场中目标声场还原与重建的等效源方法

为消除在非自由声场中重建声场时干扰声源对重建效果的影响,提出一种采用单个测量面上的声压和质点振速作为输入、等效源法作为分离和重建算法的非自由声场中目标声场还原与重建方法。该方法首先利用单面声压-质点振速测量和基于等效源法的声场分离技术将测量的混合声场分离为来自目标声源的向外传播的声场和来自干扰声源的向内传播的声场,然后利用向内传播的声场和目标声源的边界条件计算出干扰声在目标声源表面产生的散射声场,并将其从向外传播的声场中去除,还原出目标声源在自由声场条件下的辐射声场,最后利用还原的声场实现目标声场重建。通过数值仿真和实验检验了该方法的有效性和必要性。仿真和实验的结果表明,该方法可以在非自由声场的测量条件下,有效地去除干扰声的影响,实现目标声场的准确重建。      

An equivalent source method for recovering and reconstructing the target sound field in a non-free field

In a non-free field,the existence of disturbing sources would destroy the free-field condition required by near-field acoustic holography,and confuse the identification of target source due to the scattering effect caused by disturbing sound falling on the target source.To totally remove the influence of disturbing source,a method for recovering and reconstructing the target sound field in a non-free field was proposed based on the equivalent source method and the pressure-velocity measurement.In the proposed method,the sound field separation technique was firstly used to separate the mixed sound field into the outgoing field coming from the target source and the incoming field coming from the disturbing source.Then the scattered component contained in the outgoing field was calculated by using the disturbing sound and the surface impedance of the target source.Finally,the sound field radiated by the target source in a free field was obtained by subtracting the scattered component from the outgoing field and was further used to reconstruct the sound field of the target source.The proposed method was numerically and experimentally testified and the results of both the simulation and the experiment demonstrated the validity of the proposed method.     

基于时域多普勒修正的运动声全息识别方法

由于运动声源测量信号中多普勒效应的存在,一般声全息方法无法直接使用,而阵列信号波束成形处理方法无法进行定量分析.本方法建立了基于测量面、辐射面和全息面的运动学几何关系,提出了声源与测量信号之间的非线性时间映射方法,基于运动声源的声源特征函数,构造了消除多普勒效应的全息面时域声压分布.全息重建得到运动声源表面有效声压分布,实现了对主要声源处声压幅值的定量估计.实际运动声源的测量实验结果证明了该方法的有效性.     

Pekeris波导中简正波的复声强及其应用

在Pekeris波导模型下,关注了简正波的矢量场,讨论了简正波水平复声强和垂直复声强的表述,并分析了其特征.单阶简正波在水平方向是行波,相应的水平复声强仅为有功的;在垂直方向为驻波,相应的垂直复声强仅为无功的.而多阶简正波相互干涉,因此总声场的复声强既有有功分量,也有无功分量,其中只有有功分量参与声能的输运,但无功分量是反映声场信息的重要组成部分.通过对垂直(交互)复声强无功分量和水平交互复声强有功分量的数值分析,对于甚低频率的点源声场,发现当声源深度变化时,上述声场分量的正负号呈有规变化,当接收传感器置 关键词： 目标深度分类 复声强 矢量场 Pekeris波导     

Rearrangement of the horizontal space-time structure of the sound field in shallow water in the presence of moving internal waves

The rearrangement of the space-time structure of the sound field in a shallow-water waveguide with a moving intense internal wave packet is considered. The analysis is performed in terms of an approach characterized by space-time horizontal rays and vertical modes. It is shown that, within the time the packet travels over the acoustic track (about an hour), considerable spatial and temporal fluctuations occur in the field intensity and interference structure.     

高浓度沙泥沉降建模及对声传播能量的影响分析

对非刚性水下目标和事件的检测是水下安全警戒的重要内容之一。论文以港口疏浚导致的短时海区内高浓度沙泥侵入为例,探索基于声传感器收发分置的非刚性水下目标检测方法。基于沙泥沉降和声线传播模型,研究非刚性目标在沉降过程中形状、位置变迁对声传播能量及结构的影响规律。计算机仿真与海上实验均表明,局部高浓度泥团在沉降过程中,其形状、密度等指标参数会随时间发生变迁,并对经过其沉降区域的声线能量及结构造成明显影响。通过检测接收声信号能量、结构随沙泥沉降变迁的关系,可实现对水下侵入目标存在性的检测,并为开展进一步的反演、跟踪提供支持,具有一定的研究意义和参考价值。      

Patch nearfield acoustic holography in a moving medium

To realize the accurate reconstruction of sound field in a moving medium under the condition of limited holographic aperture, a patch nearfield acoustic holography (NAH) in a moving medium is proposed. The proposed method not only reduces the influence caused by the limited aperture effects through sound field extrapolation, but also perfectly suits for sound field reconstruction in a moving medium by improving the shape of the modified Tikhonov regularization filter and the noise estimation method in accordance with flow effects. In the method, two cases that the flow direction is parallel to and perpendicular to the hologram surface are considered. Especially in the perpendicular case, the expression of the wavenumber component in the z direction is improved to make the proposed method suitable for the moving medium at a high Mach number. Simulations are investigated to examine the performance of the proposed method and show its advantages by comparing with NAH in a moving medium and the conventional patch NAH. It is found that, the proposed method is effective and robust at different flow velocities of the medium and different frequencies of the sound source.     

Experimental study on variation of acoustical resonance frequency of duct with orifice depending on periodic motion

Recently, a linear compressor has been actively developed to improve the energy efficiency of home appliances, such as refrigerators. Unlike a reciprocating compressor, the suction part of a linear compressor is periodically moving. Therefore, the suction valve and the muffler constituting the suction part are periodically moving. However, up to now, there has been no research into the characteristics of the sound propagation in a periodically moving acoustic system. Thus, in this study, characteristics of sound propagation in a periodically moving acoustic system were investigated for the first time. Among a variety of acoustic filters used in a suction muffler, the change in the orifice impedance has been observed because this change is considered to be easily affected by periodically moving. Due to difficulty in measuring the orifice impedance in a periodically moving acoustic system, the change in the orifice impedance was predicted from the change in the input impedance of the suction muffler that included orifice. The experiments were carried out while changing the diameter and the pattern of orifice as well as length of the duct. As a result of experiments, the impedance of periodically moving orifice was changed depending on diameter, pattern of orifice and frequency band. Therefore, if periodically moving orifice was used to design a suction muffler in linear compressor or acoustic system, the change in the orifice impedance should be taken into consideration.     

浅海声速剖面与移动声源的跟踪定位

在水平非均匀分布的浅海环境中,针对移动声源跟踪时,声速剖面的变化会对声场产生影响,提出了一种利用集合卡尔曼滤波算法的声速剖面跟踪反演和移动声源跟踪定位的方法。首先,将声速剖面进行距离和深度的参数化表示,从而将对声速剖面的跟踪转化为对声速剖面前3阶经验正交函数系数的跟踪;其次,通过将声源状态信息和声速剖面信息表示为状态变量,而将垂直线列阵接收到的声场信息作为测量值建立状态-测量模型,然后利用集合卡尔曼滤波方法对模型状态变量进行跟踪。仿真结果得出:声速剖面跟踪反演的均方根误差和移动声源跟踪定位的绝对误差都非常小,对声源的跟踪定位精度很高。并且通过增加集合样本数、增加接收信号信噪比以及增加接收阵元数目都可以提高跟踪定位结果精度。最后,利用东海实验数据对本方法进行了验证。      

An effective quiescent medium for sound propagating through an inhomogeneous,moving fluid

The idea of similarity between acoustic fields in a moving fluid and in a certain "effective" quiescent medium, first put forward by Lord Rayleigh, proved very helpful in understanding and modeling sound propagation in an atmosphere with winds and in an ocean with currents, as well as in other applications involving flows with small velocity compared to sound speed. Known as effective sound speed approximation, the idea is routinely utilized in the contexts of the ray theory, normal mode representation of the sound field, and the parabolic approximation. Despite the wide use of the concept of effective sound speed in acoustics of moving media, no theoretical justification of Rayleigh's idea was published that would be independent of the chosen representation of the sound field and uniformly apply to distinct propagation regimes. In this paper, we present such a justification by reducing boundary conditions and a wave equation governing sound fields in the inhomogeneous moving fluid with a slow flow to boundary conditions and a wave equation in a quiescent fluid with effective sound speed and density. The derivation provides insight into validity conditions of the concept of effective quiescent fluid. Introduction of effective density in conjunction with effective sound speed is essential to ensure accurate reproduction of acoustic pressure amplitude in the effective medium. Effective parameters depend on sound speed, flow velocity, and density of the moving fluid as well as on sound propagation direction. Conditions are discussed under which the dependence on the propagation direction can be avoided or relaxed.     

Inverse aperture synthesis in an acoustic dark field

A method is proposed for extracting the signal scattered by a moving acoustic screen and for reconstructing the image of the scatterer. The results of the preliminary numerical calculations performed for a free space agree well with the results of the full-scale experiment in a lake. A good agreement between theory and experiment is achieved with an aperture synthesis by the signal magnitude. The characteristic feature of the proposed method of aperture synthesis is the use of an extended acoustic array in the target tracking mode of operation. This provides an additional condition for the determination of the parameters of the experiment, thus allowing one to determine two such parameters.     

基于测试线法的风轮近尾迹辐射噪声研究

在风洞开口实验段,针对不同尖速比应用BSWA VS302USB振动噪声采集分析系统对水平轴风力机叶尖下游4个角度的测试线进行噪声测试.叶尖辐射声中的主要成分是叶片的旋转谐波声,其向风轮下游传播的过程中迅速衰减.在各测试线上,随着测点向风轮下游移动,叶轮辐射声迅速衰减,并在一定距离之后低于背景声,尖速比越高,风轮下游辐射...     

无人机视频运动目标实时检测及跟踪

对无人机拍摄视频中的地面运动目标提出一种实时检测跟踪算法。该算法利用特征点的对应关系将图像对配准,再对配准图像进行变化检测,根据变化和运动信息检测目标并消除虚警,将检测与跟踪相结合,对目标跟踪失效的情况,能重新正确定位目标,从而获取目标的完整运动轨迹。采用无人机拍摄的地面车辆图像的测试结果表明,算法能有效检测跟踪运动目标,并能达到25 f/s以上的实时处理速度。     

Acoustic localization scheme and accuracy analysis for underwater vertical moving target using seabed stations

To measure the trajectory of an underwater vertical moving target(UVMT) in transient motion with high accuracy and high frame rate,an acoustic localization model using seabed stations with an acoustic beacon was presented.A solution algorithm based on the Gauss-Newton method was derived,which was shown to satisfy the local linear convergence.Accuracy analysis of the numerical simulation indicated that the station location,sound velocity,and signal time delay estimation errors were propagated to location parameters through measurement ranges,and the main affecting factors included the station geometry,target relative location,and acoustic conditions.Vertical accuracy was improved using a supplemental surface station coupled with the seabed stations.Detailed characteristics were indicated by accuracy distribution from the full test sea area.A 14-station array composed of 13 seabed stations and 1 surface station in a test sea of 1 km x 1 km and 60 m in depth demonstrated that the average root mean square errors(RMSEs) in the x,y,and z directions were 0.30,1.47,and0.34 m,respectively,in the vertical range of 35-60 m.This work provided a technical approach for UVMT localization,which would be useful for designing related measurement systems.     

实时多运动目标提取与跟踪研究

介绍一种静止背景条件下实时多运动日标提取与跟踪的方法。使用了单模态背景模型,用连通检测的方法分割出目标,取得目标信息,采用特征参数匹配的方法跟踪目标。对实际中出现的目标停止移动、被背景遮掩和相交运动等情况做了分析。通过采集的图像序列证实采用所提出的运动日标提取与跟踪算法可获得良好效果。     

目标机动未知下的有源声呐跟踪滤波方法

为解决由有源声呐测量误差而引入的目标机动判决模糊问题,提出了基于延迟机动检测的跟踪滤波算法。利用多假设跟踪方法,在目标机动检测模糊时,生成匀速及机动的两种目标运动假设以延迟最终的决策时间,基于残差序列构造假设检验统计量,实施序列似然比检验并融合强跟踪滤波器和Kalman滤波器的优点,提高了有源声呐对先验信息未知目标的跟踪能力。通过仿真分析表明,该算法不仅能够精确的跟踪匀速运动目标,而且能够稳定的跟踪机动目标。海试数据处理进一步验证了算法跟踪真实水声目标的有效性。      

Sound radiation into air by a point source moving underwater

Based on the discovery that the majority of radiated energy of a stationary sound source in shallow water is into the air at infrasonic frequencies, the sound transmission into air from a point source moving underwater is investigated in this letter. It is found that a moving sound source can radiate more acoustic energy into the air than a stationary one and the amount of energy radiated into the air increases with the speed of the moving source. Simulations show that the sound transmission into air is dominated by the inhomogeneous waves generated by the moving source.