Initial transients in free reed instruments: A survey of experimental results

Abstract

For free reeds in steady oscillation, the fundamental transverse beam mode dominates, but transverse modes and some torsional modes are also typically present. The motion of the free-reed tongue in early stages of the initial transient has been studied experimentally with the aim of determining the presence of higher modes and their possible role in the attack transient. These transients have been studied for free reeds mounted on a wind chamber with several methods used to initiate the attack transients. The resulting displacement and velocity waveforms have been studied using laser vibrometry, variable impedance transducer proximity sensors, and high speed video with the tracking software. The most realistic procedure used a pallet valve mechanism simulating the attack transient in a key-operated instrument. Short-term spectra derived from the waveforms have been analyzed, showing that both higher transverse modes and some torsional modes are observed in the initial transient, with the second transverse mode and the torsional mode especially prominent in the earlier stages of oscillation. Comparisons of reed tongues of different designs have been made to explore the role of these modes in the initial excitation.