Re: Midterm Question - Sort of

[Leigh Palmer <palmer@SFU.CA>]

> Leigh, the trombone, trumpet, bugle and I suppose other brass are clearly
> harmonically driven -- musicians please speak up here -- ie the lips must
> vibrate at the frequency of the desired note -- or maybe at an
> harmonic.  The instrument is merely a resonant cavity to amplify the sound
> made by the lips -- as opposed to the winds and reeds, which amplify broad
> spectrum noise in the case of the reeds and define the frequency in the
> case of the winds.

The lips are "tuned" by reflections from the cavity. They open and close
at the frequency dictated by impedance minima (or is it maxima?) which
are sensed by the musician and "centered" by feel. The musician merely
adjusts tension and pressure, DC controls. There's no way he could flap
his lips at the frequencies of musical notes and produce sufficient
power without the cavity as an impedance matching device. The instrument
is passive. There's no way it can amplify; it has no power source but
the musician's breath. I'm at home now, without my musical acoustics
texts, but several good texts describe this system, (e.g. Olson,
"Musical Engineering").

Leigh