Attack transients in free reed instruments

Abstract

Attack transients of harmonium-type reeds from American reed organs have been studied in a laboratory setting with the reeds mounted on a wind chamber. Several methods were used to initiate the attack transients of the reeds, and the resulting displacement and velocity waveforms were recorded using a laser vibrometer system and electronic proximity sensors. The most realistic procedure had a pallet valve mechanism simulating the initiation of an attack transient that depressing an organ key would provide. Growth rates in vibrational amplitude were then measured over a range of blowing pressures. Although the fundamental transverse mode is dominant in free reed oscillation, the possibility of higher transverse modes and torsional modes being present in transient oscillation was also explored. The reeds studied are designed with a spoon-shaped curvature and a slight twist at the free end of the reed tongue, intended to provide a more prompt response, especially for larger, lower-pitched reeds for which a slow attack can be a problem. The effectiveness of this design has been explored by comparing these reeds with equivalent reeds without this feature. [Work supported by National Science Foundation REU Grant PHY-1004860.]