Center for Fluid Flow and Acoustics, Division of Physical Metrology, Korea Research Institute of Standards and Science 267, Gajeong-ro, Yuseong-gu, Daejeon 305-340, Korea.
J Acoust Soc Am. 2013 Jul;134(1):237-45. doi: 10.1121/1.4809651.
Time-selective windowing techniques, which effectively remove multi-path noise, have been widely utilized for reciprocity calibration of microphone there are still limitations imposed by overlapping signals, particularly at low frequencies and for high Q microphones. Based on a fast Fourier transform analysis, the leakage due to a limited frequency range makes the overlap problem worse, not be perfectly separated. Instead of using conventional low-pass filters that are designed to have a flat response in the frequency range of interest, in this study, a filter with a Dolph-Chebyshev window shape was proposed because it has low sidelobe levels. After removing multi-path noise with a time-selective window, an inverse filter should be applied to compensate for distortion created by the applied filter. The method suggested in this paper extends the possible frequency range of free-field reciprocity calibration to frequencies below 2 kHz.
时间选择窗技术，可有效去除多径噪声，已广泛应用于麦克风的互易校准。但重叠信号仍然存在限制，特别是在低频和高 Q 麦克风时。基于快速傅里叶变换分析，由于频率范围有限而导致的泄漏会使重叠问题更加严重，无法完全分离。本研究提出了一种采用 Dolph-Chebyshev 窗形状的滤波器，而不是使用旨在在感兴趣的频率范围内具有平坦响应的传统低通滤波器，因为它具有较低的旁瓣电平。使用时间选择窗去除多径噪声后，应应用逆滤波器来补偿应用滤波器产生的失真。本文提出的方法将自由场互易校准的可能频率范围扩展到 2 kHz 以下。
