Primary sound standard based on dynamic Fabry-Pérot refractometry

Akobuije Chijioke, Richard A. Allen, Steven E. Fick, Benjamin J. Reschovsky, Jared H. Strait, Randall P. Wagner

Abstract

We describe an optical sound standard in which the sound pressure is measured by using a high-finesse optical cavity to observe the induced change in the refractive index of the medium (acousto-optic effect). The optical refractive index of a substance varies with density, and for a compressible substance it will therefore vary in time in an acoustic field. To accurately measure the refractive index changes due to acoustic density variations, we enhance the induced optical phase shifts using a high-finesse optical cavity. By tracking the shift in the optical cavity resonance frequency we sensitively track the shift of the refractive index of the cavity medium and thereby the acoustic pressure in the cavity. We perform the optical measurement at standard telecom wavelength (1550 nm), thereby minimizing the cost of the optoelectronic components required. We report initial measurements in an acoustic resonator, comparing the pressure indicated by the optical cavity to the pressure indicated by a condenser microphone, at 1 kHz and 2 kHz acoustic frequencies.

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IMEKO-TC16-2023-15.pdf

DOI

10.21014/tc16-2023.15

IMEKO TC

TC16 - Pressure and Vacuum Measurement

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