Jet displacement in edge tone, pipe oscillation, and the precursor.

Abstract

Hot-wire jet-velocity profiles are obtained at evenly spaced times throughout the steady-state acoustic cycle. Jet displacement due to an imposed acoustic crosswind at the flue exit is studied as well as that in spontaneous oscillation. The parallel-plate geometry of Coltman [J. W. Coltman, J. Acoust. Soc. Am. 60, 725–733 (1976)] is used in the edge-tone observations. Here, and also in pipe configurations, the fundamental-frequency jet displacement near the flue exit has a small phase lead relative to the transverse acoustic velocity. The acoustic radiation due to the external jet flux combines with that due to the acoustic current in the mouth in such a way as to make the external spectrum differ from that to be expected from the internal spectrum corrected for the passive acoustic transmission characteristic of the mouth; e.g., for a wide-scale stopped pipe the second harmonic amplitude is greatly enhanced in the external spectrum, and the third greatly reduced. Results for the precursor, an initial transient signal not sensitive to the pipe length, are considered briefly.