Suitability of Laser Doppler Velocimetry for the Calibration of Pressure MicrophonesReport as inadecuate

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1 LAUM - Laboratoire d-acoustique de l-université du Maine 2 Acoustics and Fluid Dynamics Group

Abstract : The details of a new approach for absolute calibration of microphones, based on the direct measurement of acoustic particle velocity using Laser Doppler Velocimetry LDV, are presented and discussed. The calibration technique is carried out inside a tube in which plane waves propagate and closed by a rigid termination. The method developed proposes to estimate the acoustic pressure with two velocity measurements and a physical model. Minimum theoretical uncertainties on the estimated pressure and minimum measurable pressure are calculated from the Cramer Rao Bounds on the estimated acoustic velocity amplitude and phase. These uncertainties and the minimum measurable pressure help to optimize the experimental set up. Acoustic pressure estimations performed with LDV are compared with acoustic pressures obtained with a reference microphone. Measurements lead to aminimum bias of 0.006 dB and aminimum uncertainty of 0.013 dB on the acoustic pressure estimation for frequencies 1360 Hz and 680 Hz.

Mots-clés : Microphone calibration LDV PIV CRB Uncertainties Pressure estimation

Author: Anne Degroot - Robert Macdonald - Olivier Richoux - Bruno Gazengel - Murray Campbell -



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