混响场中用相关传声器识别声源直达声的近似工程法

本文研究了在混响场中用相关传声器识别主声源直达声的近似工程法，包括理论及实验技术。采用该方法对一个置于混响声污染下的恒定声源进行了直达声测量，并将测量结果与该恒定声源的消声室测量结果进行了比较，结果表明：相关传声器近似工程法在很大程度上能减少混响声对主要源声压测量的干扰，从而能在混响声场中获取一定精度的主声源声压级。     

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。     

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。      

线性和非线性单频混响声场空间起伏的初步研究

对于线性单频混响声场的统计特性的研究人们曾做了许多工作,建立了均方根声压和平均声能密度统计分布理论。本文在此基础上推导出声压级统计分布函数,并把处理方法推广到混响室内在强大声源激发下的非线性单频混响声场,求得各谐波声场和总声场的统计分布函数。本文实验采用数字测量技术,对混响声场进行了大量的测量,得到的实验结果与理论符合良好。     

匹配场处理舰船辐射噪声级估计方法

针对水声信道对舰船辐射噪声声传播的影响,进而导致声源级测量结果不准确的问题,提出了基于匹配场处理的舰船辐射噪声级估计方法。在海洋环境噪声为空间均匀高斯白噪声的假设下,当海洋环境参数已知、信噪比满足一定要求时,匹配场处理能有效地给出被测噪声源的位置信息及该位置处的能量响应。从能量估计角度出发,推导了声源位置处匹配场输出响应的能量修正因子计算公式,从理论上证明了匹配场处理在被测声源位置处输出响应与能量修正因子的乘积为真实声源级的最小方差无偏(MVU)估计。该方法首先选择合适的声场计算模型计算拷贝场向量,对接收到的辐射噪声信号进行匹配场处理,得出接收信号级和被测声源位置;其次利用该位置所对应的拷贝场向量替换能量修正因子公式中的真实信道传输函数以计算能量修正因子的估计值;最后由接收信号级与能量修正因子估计值相乘得出舰船辐射噪声声源级的MVU估计。针对典型的浅海水声信道,进行了计算机仿真试验,结果表明:该方法能有效地进行舰船辐射噪声测量,当信噪比满足一定要求时,测量得到的声源级与实际声源级相比,误差小于1 dB。      

混响声场的有源控制

本文对室内声场的有源控制问题进行了探讨。发现直达声是指向性的,除非用同样指向性的反声源如对户外大型噪声源那样,是不能用有源控制的。但混响声场是驻波场,在屋角的次声源可以激发所有驻波(简正振动),因此可以作适当调制使其抑制整个混响声场。理论分析和初步实验证实此点,取得令人鼓舞的结果。对于须待解决的问题也进行了讨论。     

基于声能密度模型的中高频复杂声场预报方法

提出并推导了一种基于声能密度分布方程的声场预报方法。在能量和功率流的本构关系基础上建立声能密度平衡方程。应用直达声场和反射混响声场的叠加原理和边界面散射模型,建立了面向中高频复杂声场细节预报的数值计算方法。通过有限元计算结果在一个简单声场模型上对此方法做了验证,对比结果显示了声能密度法预报有可靠的精度和准确度。      

水听器线列阵近场声压测量误差实验研究

本文介绍了用于近场声压的测量水听器中阵元水听器测量声压的可靠性检验方法和实验结果,提出了元水听器测量球面波场中声传播衰减的曲线与现想球面波声场中场传播衰减的曲线对比的检验,要用球面声源声中心测量值对收发距离进行修正的方法,实验水池中对线列阵上十元水吸器在球形声源水池中进行了传播衰减曲线的测量分析,验证了基阵的弱散散射性能,表明线阵可用于距离小至1／7波长的极近场的扫描测量。     

光电检测方法在大功率气流声源实验研究中的应用

内流场和调制面积的准确测量是大功率调制气流声源实验研究中的关键问题,传统测量技术具有明显的局限性。采用光电检测方法以实现速度场和声源调制面积的非接触测量,通过粒子速度成像技术获取声源气路系统中的速度场,通过CCD系统实现对声源振动系统位移输出和调制面积变化的实时监控。实验结果与数值模型结果的比较验证了测试方法的可行性。速度场结果表明,典型工况下受限射流靠近内侧壁面,流动分离出现在外侧壁面附近,声源内部形成的剪切层位于主流与回流之间。音圈位移实测结果说明所选择的驱动参数可实现对喷口射流的满调制。     

基于双传声器对的多声源二维定位跟踪算法

提出一种房间混响声场环境下的多声源二维定位跟踪算法。研究了基于盲源分离的时延估计,以及联合空间分布的多个传声器对的定位算法。用高斯似然函数解决在多源、多维情况下声源定位的时延匹对模糊问题,使之能够用双传声器对实现对多个声源的二维定位,结合粒子滤波算法实现对多个运动声源的跟踪。仿真实验验证了提出算法的有效性。      

Application and measurement of underwater acoustic reciprocity transfer functions in reverberant sound field

The reciprocity measurement theory in anomalous reverberant sound fields was investigated.An improved method Was proposed due to the interrelated errors.The source volume velocity Was corrected by spatial average of measurement results and evaluation of the reverberant sound field influence on acoustic energy density.The result was validated in underwater experiment,corrected reciprocity measurement results were almost the same as direct measurement results.It indicates that reverberant sound field does not affect the validitv of the principle,but influences the obtainment of source volume velocity,then influences the measurement of transfer functions with the principle.The proposed method is simple and effective in anomalous reverberant sound fields.The study mav be valuable for the applications which are based on the principle.     

A modified electro-acoustical reciprocity method for measuring low-frequency sound source in arbitrary surroundings

The reciprocity principle provides a possible means of measuring the low-frequency volume velocity of a sound source in arbitrary surroundings; however, the auxiliary transducer in the reciprocity experiment is required to be absolutely reciprocal, which means that the radiation property and the receiving property of the transducer are identical. However, it is not always easy to obtain such a low-frequency reciprocal transducer, because some issues like nonlinearity would lead the transducer to be non-reciprocal. In this study, a modified method is proposed to conduct the reciprocity measurement using an ordinary loudspeaker instead of a strictly reciprocal one as the auxiliary transducer. Firstly, the relationship is established between the measurement error and the inconsistency of auxiliary loudspeaker’s radiation property and receiving property. Furthermore, a modified reciprocity method is proposed to compensate the inconsistency. Finally, experiments are carried out with the modified reciprocity method in both an anechoic room and a reverberation room with two different auxiliary loudspeakers. The experimental results of the modified reciprocity method agree with the results obtained with the free field method very well.     

基于等效源法和双面质点振速测量的声场分离方法

目前基于等效源法的声场分离方法有两种输入方式, 一种以双测量面上的声压为输入, 另一种以单测量面上的声压和质点振速为输入. 本文以双测量面上的质点振速为输入, 提出一种新的基于等效源法的声场分离方法. 首先给出了该方法的理论推导, 然后通过数值仿真和实验验证了该方法的有效性. 通过与基于双面声压测量的声场分离方法的比较, 证明了该方法在分离质点振速方面的优越性. 此外, 在仿真中还研究了干扰声源强度和测量面间距对分离精度的影响. 关键词： 声场分离 质点振速测量 等效源法 近场声全息     

Corrected Statistical Energy Analysis Model in a Non-Reverberant Acoustic Space

Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. This study investigates the application of the corrected SEA model in a non-reverberant acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the classical SEA model assumption is based on. A corrected SEA model is proposed where the direct field component in the energy is removed and the power injected in the subsystem considers only the remaining power after the loss at first reflection. Measurement was conducted in a box divided into two rooms separated by a partition with an opening where the condition of reverberant and non-reverberant can conveniently be controlled. In the case of a non-reverberant space where acoustic material was installed inside the wall of the experimental box, the signals are corrected by eliminating the direct field component in the measured impulse response. Using the corrected SEA model, comparison of the coupling loss factor (CLF) and damping loss factor (DLF) with the theory shows good agreement.     

波场合成中声像感知距离重建

声像距离是声像位置的重要信息,为了完整地描述重建声场中感知声像位置,需在虚拟声场中重建出声像距离。本文基于人耳对距离的感知机理,将镜像法引入波场合成技术中,通过模拟反射声来控制感知声像距离。基于"比较判断律"的主观测听实验表明:通过模拟房间反射声受试者更明显地感受到声像距离的变化,并且变化规律与人耳对距离的感知机理相符合。因此在基于波场合成的声重放系统中,通过模拟反射声和有效地控制反射声能量可以准确地重建出声像距离。      

A Sound Field Separation and Reconstruction Technique Based on Reciprocity Theorem and Fourier Transform

We show a method to separate the sound field radiated by a signal source from the sound field radiated by noise sources and to reconstruct the sound field radiated by the signal source. The proposed method is based on reciprocity theorem and the Fourier transform. Both the sound field and its gradient on a measurement surface are needed in the method. Evanescent waves are considered in the method, which ensures a high resolution reconstruction in the near field region of the signal source when evanescent waves can be measured. A simulation is given to verify the method and the influence of measurement noise on the method is discussed.     

基于声压场描述的扩散声场多自由度互易原理研究

应用于复杂结构中频声振分析的扩散场多自由度互易原理采用位移变量描述系统,实质为弹性波场互易原理,应用于声波场时会造成模型自由度数不必要的增加。建立基于声压描述的扩散声场受挡模型,利用声辐射模态描述扩散声场中结构的表面受挡声压;据此提出基于声压描述的扩散声场多自由度互易原理,发现扩散声场中结构表面受挡声压的互谱矩阵与该结构在自由空间中振动辐射声波的声阻矩阵成正比。该互易原理与传统的单自由度互易原理表达形式相似,但适用于任意自由度结构。该互易原理可用于扩散声场中复杂结构的表面受挡声压的自谱及相关分析,仿真研究表明当边界元网格尺寸小于声波波长的1/6(线性单元)或1/3(二次单元)时,数值解与理论解完全吻合。      

体积速度匹配分布源边界点法的特解源位置优化方法研究

在分布源边界点法中,选择特解源及特解源位置对声场计算的精度具有很大的影响。为减小声场计算的误差,提出了一种确定特解源位置的优化方法。在该方法中,采用三极子作为特解源,以1%体积速度相对误差对结构声辐射计算的上限频率进行预测,然后在计算上限频率范围内通过体积速度匹配搜索,得到体积速度相对误差最小意义下的特解源优化位置,在该优化位置处构造声压与表面体积速度之间的传递矩阵来计算声场,以减小计算误差。数值仿真结果表明:在求取的计算上限频率范围内,特解源处于优化位置时,计算误差得以显著减小。当振速测量存在一定误差时,采用该方法仍可将计算误差控制在5%以内。      

Position optimization of particular solution sources for distributed source boundary point method by volume velocity-matching

Choosing particular solution source and its position have great influence on accuracy of sound field prediction in distributed source boundary point method.An optimization method for determining the position of particular solution sources is proposed to get high accuracy prediction result.In this method,tripole is chosen as the particular solution.The upper limit frequency of calculation is predicted by setting 1%volume velocity relative error limit using vibration velocity of structure surface.Then,the optimal position of particular solution sources,in which the relative error of volume velocity is minimum,is determined within the range of upper limit frequency by searching algorithm using volume velocity matching.The transfer matrix between pressure and surface volume velocity is constructed in the optimal position.After that,the sound radiation of structure is calculated by the matrix.The results of numerical simulation show that the calculation error is significantly reduced by the proposed method.When there are vibration velocity measurement errors,the calculation errors can be controlled within 5% by the method.