均匀流动媒质中实时近场声全息技术理论与实验研究

Nearfield acoustic holography in a moving medium is a new cutting-edge research direction in the field of sound source identification. This technique can be used to identify and localize sound sources, and predict and visualize the sound field in a moving medium. However, as for the non-stationary sound sources in a moving medium, currently there is no stable and exactly real-time method for sound field analysis. In view of this, this project intends to propose a real-time nearfield acoustic holography in a moving medium, which is based on the analytical impulse response function and the numerical inverse impulse response in a moving medium, and the technique is expected to realize real-time prediction and reconstruction of the sound field in the true sense. Furthermore, this project intends to propose a real-time interpolation method for the sound pressure on the hologram plane, and the method is expected to realize optimized configuration of microphone array, and thus can effectively reduce aerodynamic background noise and equipment costs. Based on the theory of the technique to be proposed, relevant experiments in the wind tunnel will be conducted, and the corresponding measurement and analysis system will be developed. The research results of this project are not only expected to resolve the existing problems of instability and reconstruction process not in real time exactly for time-domain nearfield acoustic holography in a moving medium, but also to provide important guidance and basis for understanding the mechanism of noise generation and propagation, structural fault diagnosis and low-noise product design in the environment of moving medium.

流动媒质中近场声全息技术是声源识别领域新兴的前沿研究方向，可以实现流动媒质中声源的识别、定位及其三维声场预测和可视化。然而，对于流动媒质中非稳态声源，目前还没有一种稳定且实时性强的方法来进行声场分析。鉴于此，本项目拟提出流动媒质中实时近场声全息技术，该技术基于流动媒质中解析脉冲响应函数和数值逆脉冲响应，可以分别实现流动媒质中声场真正意义上的实时预测和重建。此外，本项目拟提出流动媒质中全息面声压的实时插值方法，实现传声器阵列的优化配置，从而有效降低气动背景噪声和设备成本。基于拟提出的理论，开展风洞实验研究，并研制相应的测量分析系统。本项目研究成果不仅有望解决现有流动媒质中时域近场声全息技术存在的不稳定性和不能实现真正意义上实时重建的问题，而且将为理解流动媒质中噪声的产生和传播机理、结构故障诊断以及产品低噪声设计提供重要的指导和依据。

流动媒质中近场声全息技术是声源识别领域较新的研究方向，可以实现流动媒质中声源的识别、定位及其三维声场预测和重建。本项目围绕流动媒质中实时近场声全息技术及其它相关问题开展了研究，研究内容主要包括：在时域-波数域利用有限差分法建立了流动媒质中非稳态声场预测的迭代模型，分析了数值稳定性条件，提出了两种修正或减少色散性误差的方法；基于时域-波数域有限差分法，建立了获取实时近场声全息技术中数值脉冲响应的方法，并通过与解析解的比较分析了数值脉冲响应的特性，为获取性能良好的脉冲响应提供了新的途径；系统分析了基于质点振速测量的流动媒质中近场声全息技术的奇异性问题，基于拉普拉斯变换推导出了非奇异的流动媒质中振速-声压传递函数，建立了一种稳定性较强的基于质点振速的流动媒质中声场重建方法；基于等效源法，对流动媒质中半空间声场重建问题进行了等效处理，建立了无需边界面声阻抗信息的流动媒质中半空间声场重建模型。研究结果表明，本项目所得结果进一步拓展了流动媒质中近场声全息技术的应用范围，弥补了该技术中存在的一些不足。这些成果将会为流动媒质中近场声全息技术的进一步发展奠定基础，同时可为处于流动媒质中的结构减振降噪，以及产品的低噪声设计提供重要的指导和依据。