I want to measure the velocity fluctuation in a air stream using two microphone. I got the data. How do i process it to get the velocity.
Dear Haidar,
You may use MATLAB and apply the two microphone based sound intensity calculation procedure for processing your data. You could find some useful resources for this purpose at Bruel&Kjaer website. In addition, for your short reference, please read the frequency domain Kalman filter as proposed by Bai et al (J. Ac. Soc. Am. 133(3), March 2013 pp 1425-1432.
Hi Rifat,
You can use the momentum conservation equation to estimate particle velocity from the gradient of the acoustic pressure. The linearized version of it is
j.w.rho.v + grad(p) = 0,
in which j is the imaginary unit, w is omega, rho is the ambient density, v is the particle velocity, grad refers to gradient and p is the acoustic pressure. You will have to approximate the gradient as the finite difference of the acoustic pressure given by the two microphones.
The principle is analogous to an acoustic intensity measurement using a pressure-pressure probe. You can find more information in
L E Kinsler, A R Frey, A B Coppens and J V Sanders. Fundamentals of Acoustics. John Wiley.
F J Fahy andJ G Walker. Fundamentals of Noise and Vibration. E & FN Spoon
Regards,
Diego
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