基于多声源模式的高速铁路噪声预测模型

基于多通道噪声振动实时采集与分析系统,利用平面传声器和高声强传声器对运行速度300km·h~(-1)以上的高速列车车体表面噪声源进行测试和分析.将高速列车声源等效为车底部线声源、车中部线声源和受电弓点声源.对列车通过时噪声测试数据进行理论计算,利用最小二乘法确定了高速列车以300km·h~(-1)速度在路堤线路上运行时3部分子声源的源强,由此建立了多声源模式下高速铁路噪声预测模型.将不同声源模式下的预测结果与实测结果进行对比,验证了该模型的有效性.该研究成果为我国制定高速铁路噪声预测标准提供了理论依据.     

向套管井外地层中定向辐射声场的数值计算

针对过套管探测地层构造的工程需要,用实轴积分法研究套管井不同胶结状况下相控线阵声源在套管井外地层中激发的纵波声场.结果表明:在套管井胶结差时透射到地层中的能量减小,但在套管井任意胶结状况下,通过改变井孔中相控线阵相邻阵元间激励信号的延迟时间均可以控制井外地层中辐射声束的角宽和偏转方向,使声波沿着预先没定好的方向辐射;与单个点声源激发的声场相比,在声束主瓣角偏转方向,地层的纵波幅度得到了明显增强,这可从根本上增加来自套管井外地层声阻抗不连续界面的反射波能量,提高信噪比和探测能力;利用相控线阵声源向井外地层中定向扫描辐射声场的技术可提高对套管井外复杂地质构造的识别能力.     

镜像地波束形成声源识别方法

为了消除波束形成声源识别时地面反射对声源识别结果的影响,给出了基于除自谱的互谱成像函数的镜像地波束形成方法.以半圆形阵列为例,基于传统波束形成方法和镜像地波束形成方法模拟的结果表明,低频时镜像地波束形成声源主瓣近似呈圆形,更接近真实声源形状,在中高频处镜像地波束形成方法相对于传统波束形成方法旁瓣水平被有效衰减,声源定位精度更高.进一步,研究了传统波束形成方法和镜像地波束形成方法在地面不同吸声特性情况下的声源识别性能,结果表明,当吸声系数较低时,镜像地波束形成仍能有效识别声源,当地面的吸声系数较高时,镜像地波束形成方法的声源识别性能变差.最后基于扬声器声源的算例试验验证了上述模拟仿真结论的正确性及镜像地波束形成在识别实际声源时的有效性.     

组合圆形活塞声源远场指向特征的仿真研究

依据本文构造的组合圆形活塞声源，导出了该声源远场指向性公式，并对其正确性和有效性进行了仿真研究。仿真果表明：这种结构和组合声源，不仅能有效地抑制副极大，减小主瓣宽度，而且所有声频均有指向性，声频愈高，指向性愈强。     

Material differences of auditory source retrieval: Evidence from event-related potential studies

Two event-related potential experiments were conducted to investigate the temporal and the spatial distributions of the old/new effects for the item recognition task and the auditory source retrieval task using picture and Chinese character as stimuli respectively. Stimuli were presented on the center of the screen with their names read out either by female or by male voice simultaneously during the study phase and then two testa were performed separately. One test task was to differentiate the old items from the new ones, and the other task was to judge the items read out by a certain voice during the study phase as targets and other ones as non-targets. The results showed that the old/new effect of the auditory source retrieval task was more sustained over time than that of the item recognition task in both experiments, and the spatial distribution of the former effect was wider than that of the latter one. Both experiments recorded reliable old/new effect over the prefrontal cortex during the source retrieval task. However, there existed some differences of the old/new effect for the auditory source retrieval task between picture and Chinese character, and LORETA source analysis indicated that the differences might be rooted in the temporal lobe. These findings demonstrate that the relevancy of the old/new effects between the item recognition task and the auditory source retrieval task supports the dual-process model; the spatial and the temporal distributions of the old/new effect elicited by the auditory source retrieval task are regulated by both the feature of the experimental material and the perceptual attribute of the voice.     

基于SYSNOISE的车内噪声主动控制研究

通过对汽车车内空间建立相应的有限元模型进行噪声主动控制研究，在某些位置布放次级声源来对模型进行降噪模拟，发现在单个次级声源或两个次级声源共同作用下，都能取得比较好的降噪量，而且两个次级声源共同作用可以抵消单个次级声源不能抵消的声模态。     

对柱状声源声辐射逆问题的探讨

对细长柱状声源的声辐射逆问题进行了探讨 其主要思想是 :把柱状声源所产生的声场中的声压表示为一组独立函数的线性组合 ,这样根据声场中声压分布就可以求解细长柱状声源的声辐射逆问题 文中运用无限长脉动圆柱算例进行了验算 结果证明 ,本文进行的探讨是可行的     

基于虚拟仪器的瞬时声响三维实时定位系统

基于平面四元方阵三维声响定位模型和互功率谱相位时延估计算法,按照虚拟仪器的设计理论,采用研华PCI—1714数据采集卡进行瞬时声响检测、激励及信号采集,由LabVIEW和Matlab混合编程进行系统控制,设计了四元同步实时声响定位系统.结果表明:该系统对瞬时声响的定位速度较快,精度理想,能进行有效实时跟踪定位.     

均匀脉动柱面声源阵高频辐射远声场特性的研究

由均匀脉动柱面高频辐射远声场处速度势函数 ,导出一类均匀脉动柱面声源阵高频时远声场处速度势、声压、声强公式。通过分析知 :这种结构的声源高频辐射具有方向性。