Suitability of Laser Doppler Velocimetry for the Calibration of Pressure Microphones

Anne Degroot (1) , Robert Macdonald (2) , Olivier Richoux (1) , Bruno Gazengel (1) , Murray Campbell (2)

1 LAUM - Laboratoire d'Acoustique de l'Université du Mans
2 Acoustics and Fluid Dynamics Group

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

Domaines: Acoustique [physics.class-ph]; Acoustique [physics.class-ph]

Anne Degroot, Robert Macdonald, Olivier Richoux, Bruno Gazengel, Murray Campbell. Suitability of Laser Doppler Velocimetry for the Calibration of Pressure Microphones. Applied Acoustics, 2007, 69 (12), pp.1308-1317. ⟨10.1016/j.apacoust.2007.09.003⟩. ⟨hal-00589266⟩