Wave separation and non-linear effects during super-high note playing in brass instruments.
Jonathan Kemp

The subject of super high notes in playing the trumpet or horn is a current area of controversy. Playing these notes might be expected to involve vibrating the lips at a frequency higher than the cut-off frequency of the horn predicted by linear acoustic theory. No reflections of acoustic energy would thus influence the player’s lip vibration. This would in turn imply that the notes would not be controlled by the instrument resonances. Statements by players contradict this theory in that they report that the super-high notes are “slotted” in that the instrument resonances influence the notes that can be played in the super-high range.

It is well known that non-linear effects occur in brass instruments in playing loud notes. This has been demonstrated by various researchers, for instance by measurement of the pressure signals which show a far greater number of harmonics at the bell in comparison to the mouthpiece. Recent research has demonstrated separation of forward and backward going waves while a horn is being played. This study will work towards wave separation within an instrument bore to demonstrate whether reflections from the instrument influence lip vibration and whether non-linear effects are always present during super high note playing.