Time domain wave separation using multiple microphones
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Methods of measuring the acoustic behavior of tubular systems can be broadly characterized as steady state measurements, where the measured signals are analyzed in terms of infinite duration sinusoids, and reflectometry measurements which exploit causality to separate the forward and backward going waves in a duct. This paper sets out a multiple microphone reflectometry technique which performs wave separation by using time domain convolution to track the forward and backward going waves in a cylindrical source tube. The current work uses two calibration runs one for forward going waves and one for backward going waves to measure the time domain transfer functions for each pair of microphones. These time domain transfer functions encode the time delay, frequency dependent losses and microphone gain ratios for travel between microphones. This approach is applied to the measurement of wave separation, bore profile and input impedance. The work differs from existing frequency domain methods in that it combines the information of multiple microphones within a time domain algorithm, and differs from existing time domain methods in its inclusion of the effect of losses and gain ratios in intermicrophone transfer functions.
Kemp , J A , van Walstijn , M , Campbell , M , Chick , J & Smith , R 2010 , ' Time domain wave separation using multiple microphones ' Journal of the Acoustical Society of America , vol. 128 , no. 1 , pp. 195-205 . DOI: 10.1121/1.3392441
Journal of the Acoustical Society of America
© 2010 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America. The article appeared in JASA 128 (1) pp. 195-205 and may be found at http://asadl.org/jasa/resource/1/jasman/v128/i1/p195_s1.
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