声源定位实验——一个具有明确应用背景和前沿技术特点的综合性实验

研制开发了一种进行声源定位的实验装置.利用波的传播特性,可以推知物体的空间位置.文章介绍了声发射平面定位的原理,自制的实验装置和实验结果.     

An improved model to predict energy-based acoustic parameters in Apulian-Romanesque churches

In this paper an improved model to predict energy relations in churches is proposed. A detailed acoustic survey was carried out of nine Romanesque churches having volumes ranging from 33 000 to 1500 m³. The measured sound level and early/late ratio showed significant correlation with the source-receiver distance, but the comparison with values predicted using theoretical models initially gave unsatisfactory results. The main difference was due to the early energy which was underestimated at points near the source and overestimated at distant points. Barron's revised theory proved to be the most reliable among the analysed models, so, in order to improve its prediction accuracy, a modified early reflected energy component was added to the direct and reverberant sound. The improved model was finally validated and the comparison between predicted and measured values gave good results.     

Near-field acoustic holography analysis of modulated sound source

When conventional near-field acoustic holography(NAH) technique is applied to sound field induced by modulated signal,the modulating frequency can not be revealed by the reconstructed results.To solve the problem,a NAH analysis methodology for modulated sound source was proposed.Firstly,Hilbert transform was introduced to demodulate the signal,and then modulating component was reconstructed by NAH technique.Both numerical simulation and experiment results demonstrate that accurate reconstruction analysis can be obtained by the proposed method.     

调制声源的近场声全息分析

为了解决传统近场声全息技术在重建调制声源声场时无法显示出调制成分的问题,先通过Hilbert变换对调制信号的声场进行解调处理,将调制信号和载波信号分离开来,然后再对调制成分进行普通的重建分析,由此提出了基于Hilbert变换的调制声源近场声全息分析方法。文中的数值仿真与试验研究均表明此方法可以有效地完成调制声源的重建分析。     

流形学习在运动声源声特征提取方面的研究*

运动声源因声信号时变性、叠加性和空时耦合性强,声数据呈现高维、非线性等特点,使得关键声特征提取困难,声特征提取方法复杂度高、数值计算量大、有效性差。因此,如何有效提取声特征并降低提取方法复杂度成为目前多源声场声源精准识别需迫切解决的关键科学问题。由此,该文提出短时傅里叶变换(STFT)和局部线性嵌入算法(LLE)联合的STFT-LLE流形学习声特征提取方法,并将此方法应用于运动声特征提取,且通过仿真实验测试对其进行了验证。该方法为运动声目标的分类识别提供了技术支撑。     

Effects of in-the-ear microphone directionality on sound direction identification

As advanced signal processing algorithms have been proposed to enhance hearing protective device (HPD) performance, it is important to determine how directional microphones might affect the localization ability of users and whether they might cause safety hazards. The effect of in-the-ear microphone directivity was assessed by measuring sound source identification of speech in the horizontal plane. Recordings of speech in quiet and in noise were made with Knowles Electronic Manikin for Acoustic Research wearing bilateral in-the-ear hearing aids with microphones having adjustable directivity (omnidirectional, cardioid, hypercardioid, supercardioid). Signals were generated from 16 locations in a circular array. Sound direction identification performance of eight normal hearing listeners and eight hearing-impaired listeners revealed that directional microphones did not degrade localization performance and actually reduced the front-back and lateral localization errors made when listening through omnidirectional microphones. The summed rms speech level for the signals entering the two ears appear to serve as a cue for making front-back discriminations when using directional microphones in the experimental setting. The results of this study show that the use of matched directional microphones when worn bilaterally do not have a negative effect on the ability to localize speech in the horizontal plane and may thus be useful in HPD design.     

Tracking-positioning of sound speed profiles and moving acoustic source in shallow water

An ensemble Kalman filter(EnKF) approach is proposed to perform sequential tracking of water column sound speed profile(SSP) using a moving acoustic source. First,the SSPs are discretized in depth and range, and are expressed by the empirical orthogonal functions(EOFs). Second, the acoustic source state information and the first three orders of EOF coefficients are expressed as the state variable, and the acoustic field information received by the vertical line array are the measured values. Successively, the state variables and measured values are used to establish the state-measure model. Last, the EnKF is utilized to track the state variables. The simulation results show that the root mean square error of SSP and the absolute error of source are all small, and thus the acoustic source tracking-positioning has high accuracy. Moreover, increasing the number of sample collection, the signal-to-noise ratio and the number of receiving elements can improve the tracking-positioning results. The method is verified using the experimental data of the East China Sea.     

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。     

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.     

可靠声路径传播特性及目标定位方法研究现状

作为深海中重要的声传播途径之一,可靠声路径声道下的环境噪声级较低,声速剖面变化和海底界面作用对其影响较小。此外,当接收水听器位于该声道下近海底水域时,可实现对近海面中近距离目标的无盲区监测。因此,可靠声路径必将成为一种重要的深海探测与定位途径。该文从可靠声路径的声传播特性着手,综合概述了可靠声路径声传播特性和相应目标定位技术方面的国内外研究现状,旨在回顾当前各项技术成果并展望基于可靠声路径的目标定位技术今后的发展趋势。     

时间反转和逆时偏移混合法中参数改变对目标检测和定位的影响*

时间反转和逆时偏移混合法能有效地抑制分层介质中界面或底面反射波的干扰,从而实现分层介质中目标的检测和定位。该文计算得到阵列阵元的疏密,目标在空间中不同位置,以及不同载波频率相应的声场图和声场等高线图,从而详细研究不同参数对目标检测和定位的影响。研究结果表明,接收阵元需要达到一定数目才能获得较好的聚焦效果;目标无论距阵列远近都可以被很好地定位,特别是离界面很近的目标也可以清晰地分辨出来;用调制载波信号可以得到在目标处更尖锐的声场分布,但周围的各处声场分布高低起伏,可能带来定位的不稳定。     

基于声源预估的波叠加组合全息声源识别方法

为解决声源识别中旁瓣效应等因素引起的虚假识别结果问题,提出了基于声源位置预估的波叠加组合全息算法。应用波束形成算法进行声源位置的预估,将预估声压峰值点作为假定声源点,通过波叠加原理建立方程组,利用声源强度求解结果构造完整全息平面,通过声全息方法重新计算重建面声压。进行了仿真和实验验证,经该算法重构后,波束形成算法产生的虚假声源处的声压得以明显降低。表明该算法可以抑制旁瓣效应等因素的影响,提高声源识别的准确率。     

有限振幅声波间的非线性相互作用对声源远场指向性的影响

根据Fenlon理论推导得到了多频声源的辐射声压.基于单频声源谐波指向性的求解方法,得到了二阶近似下的双频声源辐射出的声波相互作用时的远场指向性.分别研究和讨论了在初始辐射声压和频率不同情况下,两列波的相互作用对其中一列波的一阶波和二阶波远场指向性的影响.结果表明,声波间的相互作用对声源远场指向性的影响根据各波之间的相对初始辐射声压和相对频率的不同而有所变化. 关键词： 有限振幅声波 非线性相互作用 远场指向性     

Effects of acoustic source and filtering on time-of-flight measurements

Time-of-flight (TOF) measurements are valuable in the estimation of distances, displacements and velocities of moving objects, phase differences of wave pulses, temperature of the atmosphere, and so on. The effects of sound source on time-of-flight measurements have been investigated in this paper. The sound sources considered are: electric horn, impact noise source, aerodynamic noise from a free jet, and the Hartmann whistle. The focus of the present study is to highlight the advantage of using Hartmann whistle for TOF measurements as this device is simple and attractive, without any moving parts. Time-of-flight of sound waves is calculated by cross-correlating the signals received by two microphones. Further, the effect of signal filtering on TOF measurements is demonstrated. The results indicate that the sound source has considerable effect on TOF measurements, and the accuracy can be significantly enhanced by appropriate signal conditioning. Hartmann whistle proves to be a good candidate as an acoustic source for TOF measurement.     

Determining the direction to a sound source in air using vector sound-intensity probes

This paper is concerned with probes for measuring vector sound intensity in air using the minimum number of sound-pressure sensors. The probes consist of an arrangement of four small microphones at the vertices of a regular tetrahedron. They are connected to a digital signal processor, which determines the sound-intensity vector, using the cross-spectral formulation based on finite-difference approximations. Determining the direction of a sound source is an obvious application. To do this accurately the probes should be omnidirectional. This implies that the microphones in the probe have to be omnidirectional and to have the same response. Results in the paper show that the direction of a sound source can be determined with an accuracy of a few degrees. Two types of probes are described. One measures the sound-intensity vector in three-dimensional space. The other measures the vector in a half space such as would occur above the ground or in front of a wall.     

浅水海豚三维空间定位与发声源级测量

详细阐述了单水听器和水听器阵列进行海豚定距定位的几何模型,以及利用不同接收通道间的时延差计算空间坐标的方法,结合实验数据计算了海豚在水中的三维空间坐标和回声定位信号的声源级,并开展了海豚运动轨迹追踪分析。结果表明,相对于单水听器,水听器阵列对测量环境和海豚行为的限制较少,但对采集设备的同步性和硬件连接有较高要求。误差分析表明水听器阵列在大于3 m的距离,定位误差可降低到5%以下。研究结果为精确计算海豚发声源级及海豚的声呐性能及行为研究提供了技术支撑。     

浅水海豚三维空间定位与发声源级测量

详细阐述了单水听器和水听器阵列进行海豚定距定位的几何模型,以及利用不同接收通道间的时延差计算空间坐标的方法,结合实验数据计算了海豚在水中的三维空间坐标和回声定位信号的声源级,并开展了海豚运动轨迹追踪分析。结果表明,相对于单水听器,水听器阵列对测量环境和海豚行为的限制较少,但对采集设备的同步性和硬件连接有较高要求。误差分析表明水听器阵列在大于3 m的距离,定位误差可降低到5%以下。研究结果为精确计算海豚发声源级及海豚的声呐性能及行为研究提供了技术支撑。     

Estimation of parameters of motion of a moving sound source by digital processing of a set of Doppler-shifted underwater acoustic signals

A method is proposed for estimating the parameters of motion of a moving sound source on the basis of digital processing of Doppler-shifted underwater acoustic signals received by a set of hydrophones. A two-step approximation algorithm is used. An example of implementing the method of estimating the parameters of motion is presented for a two-hydrophone receiving system. Errors in estimating the parameters by means of the proposed method are considered.     

Sound source localization in real sound fields based on empirical statistics of interaural parameters

The role of temporal fluctuations and systematic variations of interaural parameters in localization of sound sources in spatially distributed, nonstationary noise conditions was investigated. For this, Bayesian estimation was applied to interaural parameters calculated with physiologically plausible time and frequency resolution. Probability density functions (PDFs) of the interaural level differences (ILDs) and phase differences (IPDs) were estimated by measuring histograms for a directional sound source perturbed by several types of interfering noise at signal-to-noise ratios (SNRs) between -5 and +30 dB. A moment analysis of the PDFs reveals that the expected values shift and the standard deviations increase considerably with decreasing SNR, and that the PDFs have non-Gaussian shape at medium SNRs. A d' analysis of the PDFs indicates that elevation discrimination is possible even at low SNRs in the median plane by integrating information across frequency. Absolute sound localization was simulated by a Bayesian maximum a posteriori (MAP) procedure. The simulation is based on frequency integration of broadly tuned "detectors." Confusion patterns of real and estimated sound source directions are similar to those of human listeners. The results indicate that robust processing strategies are needed to exploit interaural parameters successfully in noise conditions due to their strong temporal fluctuations.     

运动声源的边界元声全息识别方法研究

提出了一种可实现任意形状的运动结构噪声源识别的声全息方法。通过结合移动框架技术与边界元声全息技术两种算法的特点,提出利用移动框架技术将存在多普勒效应的时域数据转换成边界元声全息所需的双平面全息数据,然后由边界元法声全息公式重构任意结构表面的声学信息,实现运动结构噪声源定位。该方法既具有移动框架技术处理运动问题的快速简便,又具有边界元方法可处理任意形状问题的特点。最后在半消声水池中,对运动速度为9.96 cm/s的带帽圆柱壳体进行了试验验证,结果表明:在低速条件下,该方法能够准确反演得到该结构的表面有功声强以及声压等声场信息,从而实现噪声源定位。由于条件有限,高速验证需进一步验证。