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[Phys-L] Re: open/closed pipes



At 11:03 AM 4/25/2005, Anthony L., you wrote:
I'm looking for a complete list of all musical instruments divided into
open and closed pipes. I've searched the web, but have only found bits and
pieces here and there. I've even seen a trumpet listed both as an open AND
a closed pipe! Does anyone have a simple list or a good website that
categorizes instruments into these two types?

I suspect that "open/closed" is one of those "physics" classifications that
does
not stand up well to critical examination.

If I examine a length of coax whose far end is open or shorted, there is a
similarity in the way a pulse is reflected from the far end, with or without
a voltage inversion.

If I examine a length of coax whose far end is well-matched to its
characteristic impedance, I see a different behavior.

This is the electrical analog to a straight ended, versus bell ended pipe,
I suggest. If a straight-ended open pipe can promote reflections, which
it can, of course; then the nature of the source impedance becomes
interesting.
It is conceivable that edge blown and reed blown pipes can have source
impedances different from the impedance of the pipe itself- one supposes
that a reed might be a stop-like feature, that an edge might be an open
end like feature.
It is probably this combination of well-terminated ends versus
ends with ill-matched impedance that might be important to the overtones
in evidence. The filtration performance might similarly have 'formant-like'
effects on the behavior.

Brian Whatcott Altus OK Eureka!
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