Searching for early reflected waves after strike of Caribbean steelpan using time-resolved electronic speckle pattern interferometry

Abstract

Electronic speckle-pattern interferometry has become a popular tool for studying the operating deflection shapes and normal modes of musical instruments. Normally, ESPI is used with cameras having frame rates below 50 Hz, and the resulting interferograms are the result of a time average over many oscillations. Using ESPI with a high speed camera operating at frame rates of several thousand frames per second allows for time-resolved examinations of transient motion, and this technique has been used to study the motion immediately following the strike on a Caribbean steelpan. Caribbean steelpans are a complex system of coupled oscillators and it has been suggested that the inflections from the concave shape of the steelpan bowl to the convex shape of the note areas serves as a boundary where mechanical waves are partially reflected. High speed ESPI movies of strikes on a low tenor steelpan were acquired in an effort to search for evidence of these reflected waves.