Abstract:

Recent research into the mechanism of the lip reed flow controller provide stroboscopic confirmation [Copley and Strong, J. Acoust. Soc. Am. 99, 1219--1226 (1996)] and theoretical support [Adachi and Sato, J. Acoust. Soc. Am. 99, 1200--1209 (1996)] of the two-dimensional model of lip motion. In this model the lips undergo a rotary motion in which the phase difference between the (upper) lip's upward and outward components may shift in a manner that favors self-sustained oscillation near the impedance peaks of the air column. In the present work, the pressure difference p across the lips and the flow u into the instrument are estimated from measurements of pressures p[inf u] and p[inf d] upstream and downstream of the lips and the input impedance Z[inf d] of the instrument. The measured relations between p and u are consistent with the predictions of the two-dimensional model, and in particular illustrate how the brass player is able to vary the blown frequency both above and below the impedance maximum of a given mode. [Work supported by the Carver Foundation and a UNI Graduate College Project Grant.]