Spectral characteristics of the Helmholtz resonator driven by an air jet

Abstract

Motivated by an interest in the action of air jets on resonant systems in woodwinds, preliminary measurements have been made on the frequency spectra of several air jet driven Helmholtz resonators. Over the range of air jet velocities examined, stable oscillations dominated by a single frequency (under certain conditions harmonics are in evidence) occur in several intervals of jet velocity. Within each such interval the dominant frequency increases with increasing jet velocity. The span of frequencies associated with each interval includes the calculated Helmholtz frequency and, depending on the resonator and the interval, can be as much as an octave. The spectrum of the zone between the intervals is formed from an overlap of the extrapolated spectra of the adjacent intervals, i.e., it is marked by the appearance of two frequencies, where one is above the maximum frequency from the lower interval and the other is below the minimum frequency from the higher interval.