Time Domain Acoustical Holography and Its Applications
Time Domain Acoustical Holography and Its Applications
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作者：
J. Hald
Bruel & Kjaer的非稳态STSF测量系统的原理是作为1996年初结束的英国-欧洲研究项目PIANO的声场评估任务的一部分开发和应用的。PIANO项目涉及新的方法，使重型道路车辆能够更快，更便宜，更准确地实现ISO 362通过降噪措施。本标准规定了在类似条件下必须进行的瞬态户外车辆试验和部件故障排除。在Bruel & Kjaer的STSF系统1，2中实现的基于交叉谱的近场声全息需要平稳信号，因此不适用。非稳态STSF（NS-STSF）是时域全息（TDH）的一种实现。3 TDH处理记录的声事件，该声事件由覆盖声源的平面同时测量的压力时间历史组成。因此，不能使用非同时数据采集（扫描）-需要全尺寸麦克风阵列。与STSF相比，NS-STSF的三个最显著的优点是：1。不需要参考信号。2.对声源的固定操作没有要求。3.在整个NS-STSF测量和时域全息计算中保持全时间分辨率。因此，虽然STSF提供了关于噪声辐射位置的详细信息，但NS-STSF可以显示噪声辐射的位置和时间。虽然STSF仅考虑与参考信号相干的声场部分，但NS-STSF以声场的完整表示进行操作。本文简要介绍了NSSTSF的原理和理论，包括使用包络强度来概述有时遇到的非常复杂的时间变化。给出了一些典型的应用实例。
The principles of Bruel & Kjaer’s Non-Stationary STSF measurement system were developed and applied as a part of a sound field assessment task for the Brite-Euram research project PIANO which ended early in 1996. The PIANO project dealt with new methods to enable faster, cheaper and more accurate ISO 362 pass-by noise reduction measures for heavy road vehicles. This standard specifies a transient outdoor vehicle test and troubleshooting of components must be performed under similar conditions. Cross spectral based near-field acoustical holography implemented in Bruel & Kjaer’s STSF system 1,2 requires stationary signals and therefore did not apply. Non-Stationary STSF (NS-STSF) is an implementation of Time Domain Holography (TDH). 3 TDH processes a recorded acoustic event that consists of simultaneously measured pressure time histories from a planar surface covering the sound source. As a consequence, nonsimultaneous data acquisition (scanning) cannot be used – a full-size microphone array is needed. Compared with STSF, the three most significant advantages of NS-STSF are: 1. Reference signals are not required. 2. There are no requirements for stationary operation of the sound source. 3. Full time resolution is retained throughout the NS-STSF measurement and the Time Domain Holography calculations. Thus, while STSF provides detailed information about where noise is radiated, NS-STSF can show both where and when noise is radiated. While STSF takes into account only that part of the sound field which is coherent with the reference signals, NS-STSF operates with a full representation of the sound field. This article briefly describes the principles and theory of NSSTSF, including the use of envelope intensity to overview the sometimes very complicated time variations encountered. Some typical application examples are given.