Illuminating sound: A review of how sound can be measured using light

Abstract

Using optical methods to measure sound is of interest because it allows measurements of sound without the physical disturbances caused by microphones. Research in this area goes back 300 years to the earliest experiments in Schlieren imaging but it is only the technological advances of the last 60 years, in particular the development of lasers and computer technology, that have allowed a wider range techniques to be developed into viable methods for measuring sound. This paper has discussed a number of techniques with a focus on applying PCS for measuring absolute sound pressure at a single point and the use of LDV in the form of refracto-vibrometry for mapping 2D and 3D sound fields. These methods, whilst not the only ones in current research, show the most promise for the optical realisation of the unit of sound pressure, in the case of PCS, and for the quick and accurate mapping of sound fields, in the case of refracto-vibrometry.