ASA 126th Meeting Denver 1993 October 4-8

4aMU7. An experimental investigation of the phase difference between lip vibration and acoustic pressure in brass instrument mouthpieces.

S. Yoshikawa

Fifth Res. Ctr., Defense Agency, Japan

G. R. Plitnik

Univ. of Tsukuba, Tsukuba, Japan

Over a century ago, Helmholtz classified reed instruments as those which tend to blow closed as the blowing pressure increases (the mechanical reed instruments), and those which tend to open as blowing pressure increases (the lip reed instruments). All subsequent work has tacitly assumed that these models are correct, and although measurements on clarinet-like systems support the inward-blowing model, the outward-blowing hypothesis has been widely used as the basis for theoretical models of the brass instrument's sounding mechanism without experimental verification. As an alternate theory, the hypothesis that the vibrating lips of a brass player may act as an inward-blowing reed has been investigated. For this preliminary study, the phase difference between lip vibration and acoustic pressure was measured in several different lip-driven devices: a cylindrical tube without a mouthpiece, a French horn mouthpiece coupled to a nonresonant practice pipe, and a trumpet. By means of this experiment study, it is hoped that a definite resolution to the operating mechanism for the vibrating lips of brass players will be effected.