sound of a trumpet
On 12/9/2010 9:51 AM Dick Pierce spake thus:
The MORE interesting question is when you DO push aire
through some instruments, like the flute or recorder or
pipe organ, how does THAT work.
Well, in a somewhat analogous fashion. These instruments
all depend upon producing a thin sheet of air, which has
some turbulenace in it. The chaotic nature of the resulting
flow might initially flow more into the tube than out and
thus slightly pressurizing. That pressure wave travels to
the end of the tube (at the speed of sound, not surprisingly)
and, whethet the tube is open or closed, some of it is
reflected back down and when it gets to the point where it
started (the "mouth"), it opos the sheet out, thich sends a
slight evacuation wave on the same trip. The round-trip time
is largely dependent on the length of the tube, so the the
longer the tube, the less frequent the flip-slop occurs, and
the lower the note: the shorter the tube, the quicker the
round-trip time, the faster the flip-flop, and the higher
note.
I'd always understood that wind instruments like flutes and recorders
work because the airstream gets split (by the fipple in the recorder).
But I still have no idea how this produces oscillation. Very mysterious.
You mentioned the complex waveform produced by a vibrating reed. Maybe
similar to bowed instruments like the violin, in which the sound
generator (a sticky bow repeatedly "grabbing" and releasing the string)
produces roughly a triangular wave. (Dunno what the waveform of the
sound that emerges from a violin actually looks like, though; presumably
the body of the instrument does some wave-shaping.)
--
Comment on quaint Usenet customs, from Usenet:
To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
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