Cho Yong Thung, Roan Michael J
Department of Mechanical Engineering, Virginia Polytech Institute and State University, Blacksburg, Virginia 24061, USA.
J Acoust Soc Am. 2009 Feb;125(2):944-57. doi: 10.1121/1.3050248.
Phased array signal processing techniques such as beamforming have a long history in applications such as sonar for detection and localization of far-field sound sources. Two sometimes competing challenges arise in any type of spatial processing; these are to minimize contributions from directions other than the look direction and minimize the width of the main lobe. To tackle this problem a large body of work has been devoted to the development of adaptive procedures that attempt to minimize side lobe contributions to the spatial processor output. In this paper, two adaptive beamforming procedures-minimum variance distorsionless response and weight optimization to minimize maximum side lobes--are modified for use in source visualization applications to estimate beamforming pressure and intensity using near-field pressure measurements. These adaptive techniques are compared to a fixed near-field focusing technique (both techniques use near-field beamforming weightings focusing at source locations estimated based on spherical wave array manifold vectors with spatial windows). Sound source resolution accuracies of near-field imaging procedures with different weighting strategies are compared using numerical simulations both in anechoic and reverberant environments with random measurement noise. Also, experimental results are given for near-field sound pressure measurements of an enclosed loudspeaker.
诸如波束形成之类的相控阵信号处理技术在声纳等应用中有着悠久的历史，用于检测和定位远场声源。在任何类型的空间处理中都会出现两个有时相互竞争的挑战；这些挑战是尽量减少来自视向以外方向的贡献，并尽量减小主瓣的宽度。为了解决这个问题，大量工作致力于开发自适应程序，试图将旁瓣对空间处理器输出的贡献降至最低。在本文中，两种自适应波束形成程序——最小方差无失真响应和使最大旁瓣最小化的权重优化——被修改用于源可视化应用，以使用近场压力测量来估计波束形成压力和强度。将这些自适应技术与固定近场聚焦技术进行比较（两种技术都使用基于具有空间窗口的球面波阵列流形向量估计的源位置处聚焦的近场波束形成加权）。使用数值模拟在具有随机测量噪声的消声和混响环境中比较了具有不同加权策略的近场成像程序的声源分辨率精度。此外，还给出了封闭扬声器近场声压测量的实验结果。
