1pMU6. A linearized model of bassoon sound production: The role of auxiliary fingerings.

Session: Monday Afternoon & Evening, May 13

Time: 4:00

Author: Douglas H. Keefe
Location: Boys Town Natl. Res. Hospital, 555 N. 30th St., Omaha, NE 68131
Author: Robert H. Cronin
Location: Menlo Park, CA 94025


A quantitative theory of sound regeneration in the bassoon helps explain differences in the playing frequency and mouthpiece spectra associated with the use of auxiliary fingerings. The linearized condition for steady-state oscillations at a frequency f is 0=Y(f)+Y[inf G](f); the air-column input admittance is Y(f) and the double-reed generator admittance is Y[inf G](f), whose real part is negative (Fletcher, 1979; Thompson, 1979). The generator admittance is based upon a simple Bernoulli-type flow model, and the cane reed is modeled as a damped oscillator. Model parameter values are empirically determined and combined with measured input admittances, allowing direct comparison of Y(f) and -Y[inf G](f) at frequencies below and above the open tone-hole lattice cutoff frequency (Benade, 1960). Auxiliary fingerings produce significant differences in input admittance magnitude and phase above cutoff, and sound production is stabilized for a fingering such that the linearized condition is satisfied near a harmonic multiple of the playing frequency. The model accounts for intonation shifts associated with changes in auxiliary fingerings. While sound production in the bassoon is highly nonlinear, the fine structure of the linear air-column response at frequencies above cutoff is an essential contributor. [Work partially supported by the International Double Reed Society.]

from ASA 131st Meeting, Indianapolis, May 1996