Wall friction and resonance oppose each other in determining instrument sound radiation.

Evidence

Dissipation of sound energy at the walls (friction) is a crucial factor. For large dissipation, it does help to let out more of the sound (less reflection) at the end of the instrument—because to reflect it back down the instrument is to lose more of it than you gain back through resonance. Thus resonance and wall dissipation are locked in a battle: they suggest opposite strategies for getting more sound out of the instrument. This is precisely the issue we raised in connection with sound production competing with other sources of damping in section 10.8. Which effect “wins” depends on the position on the resonance advantage curve, and that depends on tube size and shape, and on frequency. The outcome of this battle for a modern trumpet bell could not be more pleasing to our ears: we will now show that indeed a treble boost applies at the lower end of “high” frequency, around 1000 to 1500 Hz, which is good, adding brilliance. But there is a treble suppression well above that range, mellowing the tone and removing the annoying raspy tone, which is also good! — Eric J. Heller, Why You Hear What You Hear- An…, 1517

Categorization

• XREF: Echoes section 10.8’s competition between sound production and other damping sources.