Séminaire n°18 + concert

L'acoustique du Cristal Baschet

Intervenants :  Frédéric Bousquet, Structures Sonores EURL, Le Tomple
                          François Gautier, LAUM, CNRS, Université du Maine, Le Mans
                          Jean-Loïc Le Carrou, Équipe LAM, d'Alembert, Paris

Contact : jean-loic.le_carrou (at) upmc.fr

Date : 20/09/10

The Cristal Baschet is a musical instrument which was developed by Bernard and Francois Baschet in 1952. Its sound is produced by friction-induced vibrations, resulting from the sliding contact between the musician’s finger and a glass rod. Today, the Cristal Baschet is an instrument which can cover up to five octaves and has reached a maturity that makes it a key instrument in contemporary music. This instrument is composed of four major subsystems: glass rods (also called glass bows), metal rods (called vibrating rods), a metallic support plate (called collector) and large thin panels (called sound diffusers). The aim of the paper is to provide further understanding of the acoustic functioning of the Cristal Baschet for manufacturing and musical interests. Experimental study of the instrument shows that the friction of the wet fingers of the musician on the glass rods creates vibrations which are transmitted to the collector and are then radiated through sound diffusers. Fingers’ motions show a succession of adhesion and slip phases on the rod. Such behavior is known as the stick-slip phenomenon similar to bow movements observed in violin playing. When playing, a key point is to control this stick-slip phenomenon. Drawing on similar studies on the violin and cello, we suggest here an adaptation of the Schelleng diagram which enables us to qualify the compromise between the force applied to the rod and the finger’s velocity, which are two fundamental control parameters during this stick-slip phase. The contact surface between the finger and the glass bow, and the contact conditions (presence of fat or acid on the skin, roughness, the use of multiple fingers) are other control parameters of the instrument. Despite their relevance, these parameters are not addressed in the study presented here. The proposed diagram allows us to define ranges of the control parameters which corresponds to a playable tune. 

Le séminaire sera suivi d'un concert sur Cristal Baschet.