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。      

Designing nonuniform linear arrays to maximize mutual information for bearing estimation

Estimating the bearing of a narrowband sound source using a towed horizontal array is a common array processing problem. This paper designs nonuniform linear symmetric arrays of fixed apertures for estimating the bearing of a sound source. Specifically, the hydrophone spacings for a symmetric linear array are chosen to maximize the upper bound on the mutual information between the true bearing and the estimated bearing in spatially white noise. The arrays maximizing the mutual information while nulling the forward endfire direction look significantly different from the uniform arrays commonly used in towed systems. Arrays maximizing mutual information are helpful when bearing estimation is considered as a quantization problem to assign the source to the correct partition. The optimal partitions for the array are designed using the Lloyd algorithm with an inner product distortion metric based on maximizing the likelihood function of the observations. In these approaches, increasing the mutual information and optimizing the partitions should reduce the probability of error (P(e)) in choosing the partition containing an unknown source. Simulation results with MAP and ML estimators demonstrate that the optimum arrays and partitions proposed here have a much lower P(e) than the uniform array and uniform partitions.     

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...     

圆弧形面阵自适应波束形成快速计算方法

针对圆弧形面阵估计水下目标二维波达方向的问题,提出一种降维处理的自适应波束形成方法。利用圆弧形面阵模型简化阵列内插矩阵的计算,通过垂直和水平两阶段波束加权,降低自适应波束形成维数,从而实现快速估计声源二维波达方向的目的。仿真结果表明,所提改进方法的计算量较传统二维最小方差无失真波束形成方法降低约一个数量级,且在低快拍条件下具有更明显的噪声抑制优势。湖上实验数据处理结果验证,在复杂水声环境下,所提方法具有较好的目标分辨性能。      

Sound source localization by the plainfin midshipman fish, Porichthys notatus

The aim of this study was to use plainfin midshipman fish (Porichthys notatus) as a general model to explore how fishes localize an underwater sound source in the relatively simple geometry of a monopole sound field. The robust phonotaxic responses displayed by gravid females toward a monopole sound projector (J-9) broadcasting a low-frequency (90 Hz) tone similar to the fundamental frequency of the male's advertisement call were examined. The projector's sound field was mapped at 5 cm resolution azimuth using an eight-hydrophone array. Acoustic pressure was measured with the array and acoustic particle motion was calculated from pressure gradients between hydrophones. The response pathways of the fish were analyzed from video recordings and compared to the sound field. Gravid females at initial release were directed toward the sound source, and the majority (73%) swam to the playback projector with straight to slightly curved tracks in the direction of the source and in line with local particle motion vectors. In contrast, the initial direction of the control (sound-off) group did not differ from random. This paper reports on a comparison of fish localization behavior with directional cues available in the form of local particle motion vectors.     

Transmission and radiation of acoustic oblique incident through tube arrays based on phononic crystals theory

In a utility boiler, the heat exchanger’s structure is similar to a two-dimensional phononic crystal. Based on the phononic crystal theory, this paper studies sound propagation through tube arrays as a function of the incident sound direction and the surroundings temperature. We carried out both the computational and experimental work for particular values of the pitch and diameters in the tube arrays and studied the band-gap diagram and insertion loss spectra for different angles of incidence. The first band gap is found to correspond to Bragg’s Law while the second band gap moves to lower frequencies as the angle increases. Simulations indicate also that the uneven temperature field influences the insertion loss spectrum. Results of experiments and calculations confirm that, for a particular tube array, the most important factors influencing sound propagation are incidence angle and the surrounding temperature. For the acoustic source in tube arrays, the acoustic radiation have relation with the frequency whether in the acoustic bang gap or not. The results should provide a basis for further work: both on sound source localization and low frequency sonic cleaning in large tube arrays.     

使用同心多环阵提升声源定位鲁棒性*

房间混响带来的多径失真是影响声源波达方向估计精度的主要因素之一。应用于环形阵列的相干信号子空间方法可以降低相干反射声带来的不利影响。该方法对环形阵进行谐波展开,并利用环谐波域导向矢量的频率无关特性聚焦各频率下的空间相关矩阵。但单环阵列存在展开系数零点,这会导致严重的噪声放大而降低定位的鲁棒性。该文提出了一种环谐波域的最小模同心多环阵,来缓解系数零点处的噪声放大问题。设计了一套麦克风阵列系统,用于评估同心多环阵列定位的鲁棒性。仿真和实验结果均表明:与相同孔径和阵元数的单环阵相比,使用最小模准则设计的同心多环阵列可以显著提升混响场景下的声源定位的稳健性。     

Correlation structure of the sound field produced in a deep ocean by a near-surface sound source

Experimental data obtained by studying the sound field produced in the first and second convergence zones by an omnidirectional pseudonoise source operating in the kilohertz frequency range at a depth of ～10 m are presented. The measurements of the cross correlation and the time spectra are performed for the signals received from different directions in the vertical plane by one narrow-beam, 40-m array and by two such arrays with the array centers positioned at different depths (200 and 450 m). The results of the experiments show that, for the signals arriving over different ray paths, the cross-correlation coefficients and the fluctuations of the time spectra obtained by using the reception at one depth and at two different depths are practically identical.     

Spatial coherence measurements from two L-shape arrays in Shallow Water

In the Shallow Water’ 06 experiment, two L-shape arrays (ARRAY52 and ARRAY32) were deployed. The vertical line array (VLA) components of both ARRAY52 and ARRAY32 were exactly perpendicular to the direction of sound propagation. The horizontal line array (HLA) component of ARRAY52 was exactly perpendicular to the direction of sound propagation. The HLA component of ARRAY32 was exactly parallel to the direction of sound propagation. This configuration offered an opportunity to simultaneously analyze the three dimensional (3-D) spatial coherences: vertical, transverse horizontal and longitudinal horizontal. When the source and the receivers were below the thermocline, both the vertical and longitudinal horizontal coherence lengths in units of wavelength increased with increasing range and frequency. When the source was within the thermocline, the transverse horizontal coherence length in units of wavelength decreased with frequency and exhibited weak range dependence. The text was submitted by the authors in English.     

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.     

The possibility of using the equivalent plane wave model to increase the efficiency of taking bearings of low-frequency signals in shallow water

The possibility of approximating the sound field in the region of interference maxima using the equivalent plane wave model with the actual amplitude and the average ??effective?? phase velocity calculated or measured by the phase gradient at the array aperture is discussed. The method is substantiated by studying the mode, interference, and phase structures of the low-frequency sound field along with the spatial responses of an extended linear array. For bottom-moored or towed geophysical arrays whose sizes are large compared to the wavelength, both the necessity and the possibility of reducing the error in taking the bearing of a sound source in a waveguide are justified. The use of the proposed model is recommended for approximate matching of the array to the transfer function of the waveguide to reduce the bearing error.     

一种分布式双麦克风线阵声源定位方法

分布式麦克风阵列由于比传统的单阵列具有更大的空间孔径,可以获得更好的声源定位性能,因此基于分布式麦克风阵列的声源定位方法成为当前麦克风阵列领域研究的热点之一。本文研究了一种基于分布式双麦克风线阵的声源定位方法,并进行了系统实现,从理论上剖析了该算法的定位精度与单阵列定向误差以及声源位置之间的关系,而且还揭示了声源高度扰动对该算法定位精度的影响。最后,分别通过仿真实验和实际定位系统的测试结果,验证了本文理论分析的正确性。     

线阵波束形成声强缩放方法估算声源的辐射声功率

为了解决波束形成声源识别过程中声源辐射声功率定量计算的问题,给出了阵型简洁、便于组合的线阵声强缩放模型。通过推导线阵的声强缩放系数,建立起线阵波束输出结果与声源辐射声功率之间的换算关系。无论是线阵还是平面阵的声强缩放方法,对于偏离阵列中心位置较远处的声源进行辐射声功率估算时都存在较为明显的误差。通过理论推导和仿真模拟计算,研究了同一单极子点声源在不同位置处的声功率估算偏差随频率、幅度的变化规律,发现该估算偏差只与声源偏离位置有关,而与声源自身的强度信息无关的结论,据此给出了相应的声功率估算修正方法。半消声室实验结果和声压法测量结果对比表明:修正后的线阵声强缩放方法用于中高频声源的辐射声功率计算时,单频声源的估算误差不超过1.0 dB,宽带声源的估算误差不超过1.8 dB。      

Non-line-of-sight sound source localization using matched-field processing

Acoustic diffraction allows sound to travel around opaque objects and therefore may allow beyond-line-of-sight sensing of remote sound sources. This paper reports simulated and experimental results for localizing sound sources based on fully shadowed microphone array measurements. The generic geometry includes a point source, a solid 90° wedge, and a receiving array that lies entirely in the shadow defined by the source location and the wedge. Source localization performance is assessed via matched-field (MF) ambiguity surfaces as a function of receiving array configuration, and received signal-to-noise ratio for the Bartlett and minimum variance distortionless (MVD) MF processors. Here, the sound propagation model is developed from a Green's function integral treatment. A simple 16 element line array of microphones is tested in three mutually orthogonal orientations. The experiments were conducted using an approximate 50-to-1-scaled tabletop model of a blind city-street intersection and produced ambiguity surfaces from source frequencies between 17.5 and 19 kHz that were incoherently summed. The experimental results suggest that a sound source may be localized by the MVD processor when using fully shadowed arrays that have significant aperture parallel to the edge of the wedge. However, this performance is reduced significantly for signal-to-noise ratios below 40 dB.     

The horizontal directivity of noise radiated by a rail and implications for the use of microphone arrays

Structural waves propagating along a railway rail form an extended source of sound radiation. Using an equivalent source model the distribution of this sound in a horizontal plane is investigated and shown to consist mainly of sound propagation at a particular angle to the normal. This direction is determined by the ratio of the wavenumbers in the rail and in air. Due to the extended nature of the rail as a source, the spatial distribution of the sound field in the direction along the track does not lend itself to the use of a simple directivity factor. The consequences for the measurement of noise from the rail using a microphone array are then explored. It is shown that a microphone array focussed normal to the rail does not detect most of the sound radiated by the rail. By turning the focus angle, the sound detected becomes a maximum when this angle corresponds to the angle of propagation of the sound radiation. Measurements on a test track using artificial excitation and measurements during the passage of a train confirm these conclusions.     

A directional acoustic array using silicon micromachined piezoresistive microphones

The need for noise source localization and characterization has driven the development of advanced sound field measurement techniques using microphone arrays. Unfortunately, the cost and complexity of these systems currently limit their widespread use. Directional acoustic arrays are commonly used in wind tunnel studies of aeroacoustic sources and may consist of hundreds of condenser microphones. A microelectromechanical system (MEMS)-based directional acoustic array system is presented to demonstrate key technologies to reduce the cost, increase the mobility, and improve the data processing efficiency versus conventional systems. The system uses 16 hybrid-packaged MEMS silicon piezoresistive microphones that are mounted to a printed circuit board. In addition, a high-speed signal processing system was employed to generate the array response in near real time. Dynamic calibrations of the microphone sensor modules indicate an average sensitivity of 831 microV/Pa with matched magnitude (+/-0.6 dB) and phase (+/-1 degree) responses between devices. The array system was characterized in an anechoic chamber using a monopole source as a function of frequency, sound pressure level, and source location. The performance of the MEMS-based array is comparable to conventional array systems and also benefits from significant cost savings.     

Accelerated steered response power method for sound source localization using orthogonal linear array

In microphone arrays application, it is a difficult task to accurately and fast localize sound source in a noisy, reverberant environment. In order to solve this problem, many approaches have been presented. Among them, the steered response power-phase transform weighted (SRP–PHAT) source localization algorithm has been proved robust. However, SRP–PHAT requires high computation cost for searching a large location space. To overcome this shortcoming, an improved SRP–PHAT will be presented that reduces a two-dimension searching space into a couple of one-dimension ones by using an orthogonal linear array. In this method, the parameters of direction of arrival (DOA) are separated. The main computation can be carried out independently in two one-dimension spaces, thus the computational load will be greatly cut down. Simulations show that there is no loss in accuracy in the proposed method.     

The problem of phasing linear hydrophone arrays lying on a shallow ocean bottom

The problem of phasing linear hydrophone arrays lying on the bottom of the Barents Sea is discussed by using the results of a full-scale experiment. In the experiment, a pulsed pressure source was used as a source of sound and three linear hydrophone arrays positioned at different sites served as receivers. For signals at the array’s apertures, the spatial correlation interval is estimated. Output responses of the arrays are compared with and without allowance for the spatial correlation interval of the sound field.     

吸顶式传声器阵列阵元坐标标定方法

提出了一种吸顶式传声器阵列阵元坐标的标定方法。针对在混响声场中,时延估计算法性能严重下降从而导致在标定传声器阵元坐标时产生较大误差的问题,提出了利用脉冲声源作为标定声源,并且截取脉冲源直达声的方法来抑制混响声场的影响,提高传声器阵元坐标标定的精度。建立了阵元坐标标定的误差分析模型,并以白噪声和脉冲声源作为标定声源进行数据仿真和对比分析。仿真结果表明,使用脉冲声源作为标定声源能有效地抑制混响声场的影响,获得传声器阵列阵元的准确坐标。同时,在封闭的房间内建立起孔径为3.5 m、64阵元的螺旋状吸顶传声器阵列进行了实验研究,实验结果验证了本文提出方法的有效性。