Horn players have observed that a timpani sounding nearby can interfere disruptively with their playing. During playing, the bell of the horn increases the radiation of sound out of the horn: it acts a little like the horn on an old gramphone. It can also act like the horn of an ear-trumpet, a device (predating hearing aids) that 'concentrates' sound coming into the large end of the horn. For horn players, this second property can be disturbing.

Technically, the horn behaves as an acoustic impedance matching device in both directions. In this study, we show that it is capable of transmitting sound waves from the bell to the mouthpiece with sound pressure gains of at least 20 dB near horn-playing resonance frequencies, and also transmits an overall impulse gain response of at least 16 dB. Further bore resonance interactions show gain responses of up to 26 dB, if the timpani is tuned near a horn resonance, as is usually the case.

This page is an electronic appendix to the scientific paper: Chen, J.M., Smith J. and Wolfe, J. (2014) "The effect of nearby timpani strokes on horn playing" J. Acoust. Soc. America. 135, 472-478. Copyright (201) Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America. The preceeding article appeared in (JASA 134, 2247-2255) and may be found at (J. Acoust. Soc. America).

Here we present examples of sound signals measured at the bell and in the mouthpiece during horn playing when the timpani is tuned (and struck) at the horn playing note, and away from it, showing examples of disruptive interactions occuring during horn playing.

The schematic diagram (not to scale) on the right shows one of the set-ups used to make measurements under extreme conditions, with the horn and timpani unnaturally close. We also report 'ecological' measurements with more realistic geometires. There is a microphone positioned in the centre of the bell of the horn and a microphone coupled to the mouthpiece, and their signals are presented below.