可模式识别的水声成像方法

提出一种在自由环境中可以进行模式识别的水声成像方法。利用角域滤波将空间不同入射方向的平面波在阵元域中进行分离,在成像扇面内按要求设计一系列角域带通滤波器,这些滤波器的输出就是从角通带内入射的平面波在阵元域中的快拍数据,可以实现要求输入为阵元域特性数据的目标识别和底质分类等专用的模式识别算法,角域滤波器输出的平面波快拍数据的幅度作为像素值进行水声成像。采用角域滤波的方法可以进行水声成像得到所需要的声图,并且每个像素对应着相应点目标远场平面波入射到接收阵时所产生的快拍数据。仿真和实验数据处理结果表明,采用角域滤波和利用常规波束形成所得到的声图是一样的,并且两种成像方法具有相同的稳健性。      

Uncertainty of array-based measurement of radiated and absorbed sound intensity

Patch near-field acoustic holography (NAH) coupled with an array of sound intensity probes allows separating the sound field incident on a surface from the one radiated by the surface itself. Although the measurement principle has been successfully used to separate the noise source contribution from disturbing sources and/or noise reflections, the method accuracy has not been investigated in the literature. We describe the results of experiments meant to evaluate the uncertainty in the identification of noise radiated by vibrating panels with different absorption characteristics in presence of an incident acoustic radiation using the statistically optimized near-field acoustic holography. Measurement errors were evaluated through tests performed in controlled acoustic conditions. Results evidenced that the measurement uncertainty depends on the accuracy of the microphone array positioning and on the incident sound field. These conclusions were in agreement with the results obtained by simulations in the phase of instrument optimization.     

A study on the random array generation method for moving sound source identification

Based on the problem that the generating method of random array structure is inefficient,a method is proposed to generate the random target arrays by using coaxial circular array in the polar coordinates in the premise that the array angular resolution of source identification is guaranteed.According to the principle of moving sound source identification,this work deduces the basic non-equidistance coaxial circular rings'radius,and generates target random arrays which were suitable for moving sound source identification through array partitioning,condition filtering in the polar coordinates and simulation evaluation.Finally,numerical simulation and moving car sound source identification test have been done.The analytical results show that using this method to generate random array is effective.Compared with the traditional regular arrays,the target random array has more accurate moving sound source identification performance.     

识别运动声源随机阵列生成法研究

针对随机阵列结构设计方面欠缺高效的生成方法这一问题,在保证阵列对声源识别精度的前提下,提出一种在极坐标下用于识别运动声源的随机阵列生成方法。根据声阵列识别运动声源的原理,推导了非等间距基本同轴圆环的半径,再通过降列分区、极坐标下条件筛选和模拟评价三个步骤,生成适用于识别运动声源的目标随机阵列,最后进行数值模拟和运动汽车噪声源识别实验进行验证。研究结果表明,用该方法能够高效地生成目标随机阵列,与常用规则阵列相比具有更良好的声源识别特性,并且具有准确的运动声源识别性能。      

On the steering of sound energy through a supercritical plate by a near-field transducer array

The ability to direct sound energy through the flexural vibrations of a submerged plate at various angles of incidence using a near-field transducer array is investigated. An alumina bar is placed in front of a one-dimensional, eight-element transducer array, between the array and the water. Operating in a receive mode, data were taken as a function of angle of incidence and compared to data taken without the presence of the alumina bar. The array was also operated in transmit mode and results were compared to corresponding receive mode data, showing that reciprocity holds. Results show that in fact sound energy can be steered through a plate, and that the measurement method used provides a convenient method of measuring the angular dependence of transmission through a plate, including measurements at frequencies above the plate's critical frequency. Experimental results of sound transmission versus angle of incidence of finite sized plates agree qualitatively with theoretical results from an analysis of the transmission through an unbounded flexible partition.     

水平线列阵方位—相速度联合的卡尔曼滤波方法*

传统的水下被动测向方法通过波束形成估计目标角度,水平线列阵波束形成中的参考声速应使用声传播的相速度,在被动测向中,由于声源距离未知,因此在对目标角度估计时选取的参考声速与接收阵处的相速度往往存在偏差,从而影响测向精度。本文提出了一种水平线列阵方位-相速度联合的纯方位扩展卡尔曼滤波方法,该方法引入相速度作为估计状态量以此校准参考声速,提高测向精度,进而改善了由于测向误差较大引起的纯方位扩展卡尔曼滤波算法跟踪结果发散的问题。浅海传播条件下的数值仿真结果表明,改进方法较常规纯方位扩展卡尔曼滤波算法具有更高的跟踪精度及稳健的跟踪性能。     

Sound field monitoring by tomographic electronic speckle pattern interferometry

Time-averaging electronic speckle pattern interferometry (ESPI) allows to record the phase modulation of light that has propagated through a sound field. When such data are collected from different projection directions the three-dimensional spatial distribution of amplitude and phase of the sound are obtained by tomographic back projection. The performance of such a setup increases with the number of projection directions, the number of effective resolution elements in the detector, and the number of recordings taken in averaging. These efforts, however, compete with the need for acceptable recording and processing times. Recent improvements in time-averaging ESPI enable even demanding applications in sound field monitoring. This is demonstrated in the design of a 38.5 kHz ultrasound source composed of a large number of individual piezoelectric transducer elements and intended to generate highly directive audio sound by nonlinear mixing in air (parametric array). The success of this method relies essentially on a non-intrusive control of the spatial homogeneity of the ultrasound field. Tomographic ESPI data have guided in a delicate alignment of the transducer elements yielding the expected narrowing of the angular radiation of the audio sound.     

Features of the Sound Field Structure in a Two-Channel Oceanic Waveguide

The results of experimental studies of the energy and angular structure of a sound field in the region of the Iberian Basin in the northeastern Atlantic are discussed. The experiments are carried out in a two-channel waveguide whose axes are located at depths of approximately 450 and 2000 m. A continuous pseudonoise signal in the frequency range 2.52–4.0 kHz is emitted. The signals are received by the omnidirectional hydrophones and, simultaneously, by a 10-m-long vertical array, which allows one to realize a narrow beam reception (～2.5°) in the vertical plane. The source and the receiver are located in a 500-m-thick layer within the upper sound channel. The field characteristics are measured in the course of a continuous change of distance from 1 to 65 km. The comparison of the experimental data with calculations shows that the sound field structure formed by the lower channel is much closer to the theoretical results than the structure formed by the upper channel. In the upper sound channel, the shadow zone manifests itself only slightly and the first convergence zone begins approximately 72–11 km nearer to the source than predicted by the calculations. The corresponding angular sound field structure is fairly pronounced in the vertical plane and bears no evidence of the random behavior that is peculiar to the fields scattered by the inhomogeneities.     

线阵声强缩放方法在水下声源辐射功率估算中的应用_

为了解决水下声源辐射声功率难以计算的问题,利用线阵声强缩放方法在波束形成声源识别的基础上,根据波束输出结果与声源辐射声功率之间的换算关系来获得相应的声功率.为了提高线阵声强缩放方法的水下声功率估算精度,给出了一定动态范围限制的主瓣区域积分方法,并通过仿真验证了该方法的有效性.在消声水池中开展了水下声功率估算的实验研究....     

格林函数解卷积处理的阵不变量浅海无源定位

水下声源无源定位是声呐技术重要的研究方向.针对水下声源无源定位问题,本文提出了一种基于格林函数解卷积处理的阵不变量无源定位方法.该方法使用盲解卷积算法从水平阵接收信号中提取时域格林函数,然后采用空域解卷积方法处理得到的时域格林函数,获得波束时间偏移,从波束时间偏移中计算得到阵不变量,解算目标距离,从而实现声源定位.区别...     

基于超指向性多极子矢量阵的水下低频声源方位估计方法研究

针对水下低频声源的方位估计问题,基于基元紧密排列的二维矢量阵,建立了一种超指向性波束形成方法.根据矢量基元差分运算构建各阶多极子模型,获得了几乎与频率无关的模态函数,并经加权计算可在低频条件下实现超指向性波束,以解决阵列孔径对波束性能的限制.同时,结合输出信噪比最大准则所得波束,分析了超指向性波束形成算法的稳定性与波导的影响程度,探索模态阶数与阵列参数的选取原则.通过阵列性能的仿真计算与实际阵列的测量数据表明,该算法可在小尺寸阵列孔径下获得良好的阵列波束,兼具了水下线型超指向性阵和环形超指向性阵的优点,可有效实现水下低频声源的水平方位估计;且波束性能可通过调节模态阶数与基元间距以达到最佳,并受水下声波导多途与频散效应影响有限.     

Determination of the path of a sound source moving in an inhomogeneous medium

The possibility of determining the actual paths of moving sound sources from the signals received by a linear horizontal array whose size is large compared to the wavelength is investigated with the use of procedures suggested earlier for the imaging of dynamic objects moving below an inhomogeneous layer. Two cases of signal reception are considered: when the signals propagate in the oceanic waveguide and when the signals propagate through an inhomogeneous layer located near the array. It is shown that, unlike the standard spatial processing procedures, the proposed methods allow one to measure the absolute angular displacements to within the diffraction resolution of the array and to eliminate the ambiguity in angular measurements. An important point is that the proposed methods require no prior data on the parameters of the inhomogeneous layer or the multimode waveguide.     

基于倾斜阵的距离与方位联合估计*

针对阵列倾斜引起的阵不变量方法定位精度下降的问题,该文结合倾斜阵声源定位的三维模型提出一种基于倾斜阵的距离与方位联合估计算法。该算法通过联合自校正方位距离联合估计方法对阵列倾角在声源-接收平面的投影量进行估计和补偿,改善目标距离估计误差的同时,利用匹配出的阵列倾角投影量反向估计目标方位,获得对声源二维位置的估计。通过仿真验证了该算法能够在阵列倾角较小时实现目标方位与距离的联合估计。     

单层传声器阵列重建相干声场的近场声全息方法研究

针对传声器阵列两侧存在相干声源的非自由声场重建问题,提出基于球面谐波函数扩展近场声全息理论的相干声场重建方法。该方法在已知测量面两侧声源几何位置时,使用单层传声器阵列获取测量面处的声压分布,通过最小二乘法获得与目标声源和干扰噪声源响应对应的最优球波函数扩展项数和最优系数向量,结合测点位置的空间坐标进行声波分解,并分别重建出各声源在测量面上的声压分布。为了验证方法的有效性,分别给出了相干噪声源为球形声源和非球形声源的仿真验证,并在全消声室内对双扬声器产生的相干声场的重建进行了实验验证。结果表明:该方法对球形声源和非球形声源干扰下的声场重建都具有较好的效果,球形声源干扰下的重建精度更高。      

单层传声器阵列信号空间重采样的声波分离方法

为了重构非自由声场中目标声源的声场响应,提出单层传声器阵列信号空间重采样的声波分离方法.以球面波函数为基函数,建立由系列球面波函数叠加表达的声场数学模型.基于近场声全息原理,利用单层传声器阵列面上空间重采样形成的两组声压测量信号,求解基函数系数,并重构出传声器阵列两侧声源各自的声场响应,实现声波分离.使用脉动球和振动球共同作用的非自由声场,检验了数学模型以及传声器信号信噪比、传声器阵列形状和面积、声源中心位置、频率等关键参数对声波分离精度的影响,并在全消声室内进行了实验验证.最后,对单层传声器阵列重采样的声波分离方法的实施给出了建议.     

Estimation of the location of a farfield acoustic source

A backward integration method for estimating the location of a source of sound waves in the atmosphere is presented. This geometric acoustics method is based upon the analysis of microphone array measurements to determine the incoming ray direction in three dimensions. The equations governing the propagation of the ray are then integrated backward in time. The sound source lies somewhere along the calculated ray path. The intersection of such loci from more than one array would provide an estimate of the source location. The method appears to be very rapid to implement and, assuming the time delays to be accurately measured, limited in accuracy only by the timeliness of the input sound speed and velocity profiles in the atmosphere.     

低频大孔径线列阵声纳在海底反射区的测向性能分析*

与深海直达声探测、会聚区探测不同,在海底反射声探测模式下,低频大孔径线列阵声纳采用常规阵列信号处理方法,会产生测向误差增大和方位分裂等测向性能下降现象。目前,关于海底反射声探测模式下测向性能下降程度的预报、测向性能下降现象出现的区域位置预报等方面尚缺乏研究。本文针对该问题,提出一套海底反射区声纳测向性能预报方法。该方法以深海声场存在“简正波簇”现象及高阶“简正波簇”在角谱域分布具有稳定性等分析结论为支撑,提出高阶“简正波簇”角谱域分布向空域分布的转换方法、高阶简正波簇引起的测向误差量值预报方法、不同高阶简正波簇干涉产生多目标现象的条件的计算方法,实现了对低频大孔径线列阵声纳在深海海底反射区不同位置的测向误差预报、目标方位分裂现象产生的位置和目标角度范围要求预报。结合典型条件下的预报结果,本文提出了下一步开展低频大孔径线列阵声纳深海海底反射区环境适配信号处理方法的研究方向。     

Interior and exterior sound field control using general two-dimensional first-order sources

Reproduction of a given sound field interior to a circular loudspeaker array without producing an undesirable exterior sound field is an unsolved problem over a broadband of frequencies. At low frequencies, by implementing the Kirchhoff-Helmholtz integral using a circular discrete array of line-source loudspeakers, a sound field can be recreated within the array and produce no exterior sound field, provided that the loudspeakers have azimuthal polar responses with variable first-order responses which are a combination of a two-dimensional (2D) monopole and a radially oriented 2D dipole. This paper examines the performance of circular discrete arrays of line-source loudspeakers which also include a tangential dipole, providing general variable-directivity responses in azimuth. It is shown that at low frequencies, the tangential dipoles are not required, but that near and above the Nyquist frequency, the tangential dipoles can both improve the interior accuracy and reduce the exterior sound field. The additional dipoles extend the useful range of the array by around an octave.     

Active noise control with linear control source and sensor arrays for a noise barrier

A study is conducted on minimizing the sum of the squared acoustic pressures with a linear array of control sources and a perpendicular linear array of error sensors, placed above the top of a noise barrier. Particular angular orientations, with respect to the center of the barrier top, and spacings of the linear arrays of control sources and error sensors result in moderate to significant additional reduction of the acoustic pressure in the shadow zone. Visual inspection of the sound pressure field, with and without active noise control, found that uniform and significant additional insertion loss can be generated near the barrier. Numerical simulations were conducted to test the proposed method. For separations between control sources and error sensors much less than a quarter wavelength of the primary noise disturbance, results show that the angular orientation, of the combined linear control source and sensor arrays, is a weak factor for acoustic pressure reduction in the shadow zone. Weak angle dependence serves as an advantage to the proposed method, which yields uniform performance for any angular orientation. An angular orientation involving the alignment of the furthest error sensor with the first diffracting edge of the barrier and the primary source was observed to perform well for a variety of frequencies, since the spacing between error sensors and between control sources is of the order of a quarter-wavelength. Improved noise control in the shadow zone of a barrier is achieved by the use of two control sources and angular orientation as mentioned above. Further spatial extension of the area of reduced acoustic pressure is possible by utilizing an increased number of control sources.     

瞬态波位移场计算方法在相控阵声场模拟中的实验验证

通过实验研究了声束偏转不同角度和声场半径变化时线性相控阵的声场特性,并与基于瞬态波位移解析解的相控阵声场计算方法得到的理论结果进行了对比。首先研究了基于半圆圆弧离面瞬态位移的声场计算方法,并进行了数值计算可靠性的优化。然后建立了一套相控阵瞬态波位移场的测量系统,以半圆形钢板为试件,纵波传感器为接收传感器,测量了偏转角度为-10°,-30°,-50°,-70°,及声场半径为50 mm,75 mm,100 mm和125 mm时线性超声相控阵的声束指向性;同时以基于瞬态波位移解析解的相控阵声场计算方法,计算了相同条件下该相控阵的声束指向性。最后将实验结果与理论结果进行了对比,取得了较好的一致。说明基于瞬态波位移的相控阵声场计算方法可以较好地计算线阵的声场,对于声束偏转较大角度和声场半径变化时也同样有效。