Visualisation and measurement of acoustic and fluidic phenomena using a laser-scanning vibrometer

A new method for non-interactively measuring and visualising turbulences, e.g. vortexes, and acoustic sound waves in gases is described. The measuring effect is based on the path difference Deltadelta between two interfering laser beams. This difference results from changes of the refractive index n, caused by pressure fluctuations p(t) in a measuring volume. The method is practicable in both the audio and the ultrasonic ranges, as well as for spatially small turbulences. It is adequate for the investigation and demonstration of numerous acoustic, fluidic and fluid-acoustic phenomena.