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
Résumé:
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.