Regime-change-induced modification of jet flow in flute-like instruments with a hysteresis region
Katherine L. Saenger · Proceedings of meetings on acoustics · 2022
Sound production in flue instruments (e.g., flutes and recorders) results from the interaction of an air jet with a strike edge that is coupled to a resonator. This paper presents evidence for a peculiar aspect of air jet behavior observed when a flute or recorder powered by an artificial blower is set up to play in a bistable hysteresis region where both an upper and lower tone are stable at the same blowing pressure. Under these conditions, the sounded tone is determined by the pressure history of the system, and a switch between the two tones can be accomplished by a momentary increase or decrease in the blowing pressure. An unexpected finding was that the jet pressure recorded by an external pressure probe positioned downstream of the strike edge was sensitive to the tone being played. With an optimally positioned probe, switching from one tone to the other typically produced a reproducible 20-30% change in jet pressure even though the blowing pressure remained fixed. Additional measurements suggest that this pressure change results from a macroscopic change in the steady-state angular width of the jet. It is hoped that these results will stimulate further measurements and modeling by others.