“Knocked Over!”: A visual demonstration of time reversal focusing using bending waves in a thin plate

Abstract

The purpose of this research is to develop a visual demonstration of time reversal focusing in a thin plate to be used as a teaching tool. This presentation will discuss the various plate materials tested to provide the optimal conditions for time reversal focusing. Specifically, the reverberation time in each plate and the sensitivity of the source of vibrations are quantified to provide the best spatially confined focus as well as the highest focal amplitude possible. A vibration speaker and a scanning laser Doppler vibrometer (SLDV) are used to provide the time reversal focusing. A series of objects are placed on the plate in an attempt to knock over objects near the focal location and not elsewhere. Spatial mapping of the plate vibration using the SLDV will be shown to illustrate why some objects fall and others do not.