Analysis of clarinet reed oscillations with digital Fresnel holography

Abstract

This paper describes optical instrumentation devoted to vibration analysis.Two strategies based on digital Fresnel holography are presented. The first one, called time-averaging consists in the numerical reconstruction of the hologram after recording with an exposure time much greater than the vibration period. Thus, the holograms have their amplitude modulated by a Bessel function. The last strategy, using a pulsed regime, allows the reconstruction of the full movement of the vibration, even if it exhibits very high amplitude. Experimental results presented in this paper concern the study of the vibrations of a clarinet reed under free and forced oscillation regimes.

Measurement of density fluctuations using digital holographic interferometry in a standing wave thermoacoustic oscillator

“…Thanks to the development of high resolution CCD cameras and the increasing power of computers, digital holographic/ interferometric measurements are nowadays under development and have already been used to analyze various processes of vibration kinematics [22,23] or fluid mechanics [24], but only a few works have been made to characterize the density fluctuations associated to an acoustic process. There exists pioneering works performed fifteen years ago by Wetzel and Herman [25][26][27], in which analog holography has been used to measure temperature fluctuations at the end of a couple of parallel plates submitted to a high amplitude acoustic field.…”