Experimental studies with parallel phase-shifting interferometry

Abstract

One of the most popular of devices currently used for acousto-optic sensing is the laser Doppler vibrometer (LDV), an interferometer originally designed to measure the vibration velocity of objects. LDVs are a popular way to measure and visualize acoustic fields, however it requires scanning the laser, which limits the measurement sound field. Recently, as the camera captures 2D images of the sound field on thousands of pixels simultaneously, the sound fields that can be measured are no longer limited to those that can be repeated. A high-speed camera captures 2D sound fields with tens or hundreds of thousands of frames per second, making it possible to film a slow-motion video of propagating sound in real time. The parallel phase-shifting interferometry (PPSI) with polarized high-speed cameras has been developed and introduced in the acoustics field as well. It has demonstrated impressive visualizations of airborne acoustic phenomena due to its high sensitivity and spatiotemporal resolution. It has also found many applications in recent years. This paper presents our experimental studies, especially measurement of aerodynamic sound, sound radiated from fast-moving sources or musical instruments, determination of acoustic center, etc.