Applied Research Laboratory, Pennsylvania State University, PO Box 30, State College, Pennsylvania 16804, USA.
J Acoust Soc Am. 2011 Sep;130(3):1154-63. doi: 10.1121/1.3613925.
A worldwide network of more than 40 infrasound monitoring stations has been established as part of the effort to ensure compliance with the Comprehensive Nuclear Test Ban Treaty. Each station has four to eight individual infrasound elements in a kilometer-scale array for detection and bearing determination of acoustic events. The frequency range of interest covers a three-decade range-roughly from 0.01 to 10 Hz. A typical infrasound array element consists of a receiving transducer connected to a multiple-inlet pipe network to average spatially over the short-wavelength turbulence-associated "wind noise." Although the frequency response of the transducer itself may be known, the wind-noise reduction system modifies that response. In order to understand the system's impact on detection and identification of acoustical events, the overall frequency response must be determined. This paper describes a technique for measuring the absolute magnitude and phase of the frequency response of an infrasound element including the wind-noise-reduction piping by comparison calibration using ambient noise and a reference-microphone system. Measured coherence between the reference and the infrasound element and the consistency between the magnitude and the phase provide quality checks on the process.
一个由 40 多个次声监测站组成的全球网络已经建立，作为确保遵守《全面禁止核试验条约》努力的一部分。每个监测站都有四到八个单独的次声元件，形成一公里范围内的阵列，用于检测和声事件的方位确定。感兴趣的频率范围涵盖了三十年的范围，大约在 0.01 到 10 Hz 之间。一个典型的次声阵元由一个接收传感器组成，连接到一个多入口管道网络，以在短波长湍流相关的“风噪声”上进行空间平均。尽管可以知道传感器本身的频率响应，但风噪声降低系统会改变这种响应。为了了解系统对声事件检测和识别的影响，必须确定整体频率响应。本文描述了一种测量次声元件（包括风噪声降低管道）的绝对幅度和相位的技术，该技术通过使用环境噪声和参考麦克风系统进行比较校准来实现。参考和次声元件之间的测量相干性以及幅度和相位之间的一致性为该过程提供了质量检查。
