Schlieren Imaging of Sound Fields

Abstract

In spite of the fact that Schlieren imaging is over 120 years old, it still offers surprises when analyzed with modern concepts of acousto optics. Also, such concepts are applicable to high frequencies and thick sound fields, where conventional models fail. In this paper we present a heuristic plane wave interaction analysis to determine the exact relation between the sound field and the image. The latter is expressed as an effective sound field selected by the diffraction process through a filtering operation on the plane wave spectrum of the original sound field.