Air columns for demonstration of upstream/downstream symmetry in reed wind instruments

Abstract

The acoustics of a reed wind instrument such as a clarinet or oboe, and including the lip-reed instruments such as the trumpet, are classically described by the input impedance of the instrument air column and the dynamical flow control characteristics of the reed valve. The behavior of the system is largely dependent on the resonances of the instrument air column. A fuller explanation however includes both the downstream (usually the instrument) and the upstream (usually the player's wind way) input impedances in symmetry. To demonstrate this, a clarinet-like instrument with no resonance peaks can be played using the resonances of the player's wind way. Another demonstration uses a resonant tube for the upstream air column, with the playing frequency or fundamental based upon a resonance of this upstream tube. The downstream air column has a resonance whose frequency and damping can be set independently of that other resonance. This allows exploration of the effect of a resonance at a harmonic of the playing frequency.