运动声源识别的动态波叠加方法研究

为更好地识别运动声源并解决声源识别中的虚假声源问题,基于运动声源短时信号的Doppler频移特性, 建立运动声场的短时波叠加关系, 利用波束形成方法对声源点进行预估, 基于预估建立起多运动声源的动态叠加方程, 进一步通过波叠加方程的求解进行声源的计算, 从而创建一种可以用于运动声源识别的动态波叠加方法. 该方法可以有效识别运动声源, 将波叠加方法扩展到了运动声源测量领域, 并在不增加传声器数量以及改变阵列形式的条件下有效抑制运动声源重建中的旁瓣效应, 解决运动声源识别中的虚假声源问题. 仿真及实际运动声源的测量试验结果证明了该方法的有效性.     

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。      

基于联合波叠加法的相干声场全息重建与预测理论

在相干声场中,很难将各个声源产生的声压分离开来,所以常规波叠加法不能用于相干声场的全息重建与预测。根据相干声场的叠加性,通过构造全息面与多个声源之间的联合声压匹配矩阵,建立了基于联合波叠加法的相干声场全息重建与预测理论。该理论可以精确地重构出各个声源的表面声学信息,也可以分别预测每个声源的空间声场分布,叠加后即可获得相干声场的空间分布,从而实现了相干声场的重建与预测。实验和数值仿真的结果表明:该相干声场重建与预测理论不仅能有效地解决相干声场的重建与预测问题,并且可以作为一种相干声场分离技术,拓宽了全息技术的应用范围。     

基于统计最优和波叠加的联合局部近场声全息

提出了一种基于统计最优近场声全息和波叠加法的联合局部近场声全息技术.首先利用两次统计最优近场声全息的声源定位结果来指导配置等效源,其后利用波叠加法进行局部声场重构.该技术适合于中低频卢场的局部重建,计算快速,重建精度高;可以在测量数据有缺失的情况下重建声场.进行了脉动球声源模型的数值仿真,并在半消声室内对电机噪声源进行了实验,仿真实验都准确地重构了声源所辐射的外部声场.该技术可以重建任意类球形声源辐射的声场.     

基于单元辐射叠加法的结构声源声场重建方法

为了提高分布式结构声源的声场重建精度,本文提出了基于单元辐射叠加法的结构声源声场重建方法.该方法首先利用声场叠加原理和结构振声传递特性,建立了结构声源表面振动与辐射声场之间的振声传递关系解析表达式,得到便于快速计算的振声传递矩阵,能够解决连续分布、相干结构噪声源的声传播模型精细化表征问题.然后利用振声传递矩阵作为传递算子进行声场重建,并与迭代加权算法相结合.通过将基于单元辐射叠加法的声场预报结果与解析法预报结果进行比较,验证了单元辐射叠加法具有较高的准确性.并将基于单元辐射叠加法的声场重建方法与传统等效源法近场声全息和迭代加权等效源法相比较,通过仿真分析与矩形板声场重建实验证明了基于单元辐射叠加法的声场重建方法能够改善结构声源的声场重建精度并增大近场声全息的有效测试距离范围.     

声场干涉结构相似度匹配的目标运动参数估计

针对水中运动声源定位问题,建立了一种基于声场干涉结构谱向量相似度匹配的目标运动参数估计方法。结合声场干涉结构水平纵向相关特性,利用目标辐射噪声LOFAR谱图中不同频率的谱值序列,基于两方位-两距离目标运动要素计算方法获取的目标距离解向量,构造声场干涉结构谱向量相似度匹配代价因子,实现目标运动参数估计。仿真数据与试验数据验证结果表明:在绘制的目标运动要素解算结果可视化分布图中可清晰呈现出目标初距、航向和速度结果。该算法实现过程简单、解算效率高,对目标方位误差有较好的鲁棒性。      

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.     

基于声强测量的近场声全息及其在水下声源声辐射分析中的应用

基于声强测量的宽带声全息（ＢＡＨＩＭ）是一种新的有效的声场重建技术，在获得了测量面（全息面）上两个切向声强分量后，利用ＢＡＨＩＭ可以预报声源的辐射场及噪声源定位。本文给出了不同声源和参数下ＢＡＨＩＭ数值分析结果，井利用自行研制的双通道自动扫描声强测量系统进行了水下声源近场声辐射的ＢＡＨＩＭ实验，结果证实了该方法的有效性，它增强了分析和识别噪声源的能力。     

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。     

用于声源识别的声全息重建方法的研究

研究了用于声源识别定位的声全息方法中声场重建公式。从场论及声学的基本衍射出发提出了新的声全息重建公式．利用该公式进行了模拟计算和分析,将结果与以往的一些重建公式进行了比较。利用该公式对复杂的汽车声源进行了识别,结果表明该重建公式是一种有效的复杂声源识别定位方法。     

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.     

Wave field synthesis of moving virtual sound sources with complex radiation properties

An approach to the synthesis of moving virtual sound sources with complex radiation properties in wave field synthesis is presented. The approach exploits the fact that any stationary sound source of finite spatial extent radiates spherical waves at sufficient distance. The angular dependency of the radiation properties of the source under consideration is reflected by the amplitude and phase distribution on the spherical wave fronts. The sound field emitted by a uniformly moving monopole source is derived and the far-field radiation properties of the complex virtual source under consideration are incorporated in order to derive a closed-form expression for the loudspeaker driving signal. The results are illustrated via numerical simulations of the synthesis of the sound field of a sample moving complex virtual source.     

Development and calibration of acoustic video camera system for moving vehicles

In this paper, a new acoustic video camera system is developed and its calibration method is established. This system is built based on binocular vision and acoustical holography technology. With binocular vision method, the spatial distance between the microphone array and the moving vehicles is obtained, and the sound reconstruction plane can be established closely to the moving vehicle surface automatically. Then the sound video is regenerated closely to the moving vehicles accurately by acoustic holography method. With this system, the moving and stationary sound sources are treated differently and automatically, which makes the sound visualization of moving vehicles much quicker, more intuitively, and accurately. To verify this system, experiments for a stationary speaker and a non-stationary speaker are carried out. Further verification experiments for outdoor moving vehicle are also conducted. Successful video visualization results not only confirm the validity of the system but also suggest that this system can be a potential useful tool in vehicle's noise identification because it allows the users to find out the noise sources by the videos easily. We believe the newly developed system will be of great potential in moving vehicles' noise identification and control.     

Quantitative measurement of pass-by noise radiated by vehicles running at high speeds

It has been a challenge in the past to accurately locate and quantify the pass-by noise source radiated by the running vehicles. A system composed of a microphone array is developed in our current work to do this work. An acoustic-holography method for moving sound sources is designed to handle the Doppler effect effectively in the time domain. The effective sound pressure distribution is reconstructed on the surface of a running vehicle. The method has achieved a high calculation efficiency and is able to quantitatively measure the sound pressure at the sound source and identify the location of the main sound source. The method is also validated by the simulation experiments and the measurement tests with known moving speakers. Finally, the engine noise, tire noise, exhaust noise and wind noise of the vehicle running at different speeds are successfully identified by this method.     

运动声源快速定位的声达时差法

针对声达时差法只能用于非运动声源定位的问题,本文提出一种运动声源快速定位方法。该方法以声达时差为基本定位原理,基于声源计算位置对多普勒效应进行解耦并进行声信号多普勒效应修正,根据三角定位方法构建声传播空间矩阵,以声源位置偏差度为目标基于单纯形优化搜索算法进行声源位置快速逼近,实现了对匀速直线运动的单声源的定位追踪,提高定位实时性。该方法将声达时差法拓展到运动声源的定位,同时解决了消除多普勒效应带来的计算过程复杂、运算量大的问题,仅用4个传声器就可实现运动声源的快速定位,突破了传统运动声源识别中对大传声器阵列的依赖。仿真实验和实车运动声源识别实验结果证明了该方法的有效性,本研究为短时发声运动声源的识别提供了一种简便、高效的方法。      

On the sound sources of screech tones radiated from choked circular jets

The generation mechanism of the screech tone in the helical oscillation mode is mainly investigated using a series of instantaneous schlieren photographs. From the photographs, five evanescent sound sources are observed as prominent points along the jet axis. The sound source for the dominant helical oscillation mode is found to be the second prominent point which moves along a circular orbit in a plane perpendicular to the jet axis and just downstream of the rear edge of the third shock cell. It is shown that the speed of a moving sound source is supersonic and that the Mach cone generated by the moving sound source forms the helical-shaped wave front of the screech tone for the helical oscillation mode of the jet. This idea of the moving sound source is well supported by a measured directionality of the screech tone. Sound sources of the other oscillation modes appearing in the other pressure ratio ranges are also described.     

内部体积源作用下的圆柱壳内外声场特性

圆柱壳内各型体积源辐射噪声特性研究是声场建模和声场预报的前提.为了研究具有指向性的大尺度体积源特性对水下航行器结构内外声场的影响,本文结合薄壳理论、等效源和柱腔Green函数构造了体积源激励下的壳体振动耦合方程,研究了体积源表面声散射作用和指向性强弱对圆柱壳内外声场的影响.数值计算结果表明,体积源构造的准确性与其等效源位置有关,等效源配置在体积源几何中心与其结构表面之间0.4—0.6时,可以提高声场计算结果的准确性;大尺度体积源表面的声散射作用会导致壳体内部声场结构发生改变,内声场声腔共振峰发生偏移,并且在部分频段引起较强的声透射现象;此外,体积源指向性变化对壳体内外声场强弱影响较小,其显著作用表现在改变了外辐射声场的远场指向性.该研究结果对噪声预报和控制有一定的参考价值.     

A note on moving multipole sources of sound

The object of this note is to draw attention to the need, when speaking of a moving multipole source of sound, to state whether it is based on the wave equation for the velocity potential or the wave equation for the perturbation pressure. The theory of moving multipole sources of sound is firmly established, but, owing to lack of precision, some seemingly contradictory results are to be found in the literature. The reasons for these seemingly contradictory results are examined, and various basic relationships between a moving multipole sound field and its method of generation are established.