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From: Michael Carley
Date: Wed, 3 Jan 96 9:24:38 GMT
Subject: Re: Bending & Resonant Material

> There's a difference here. A pipe is a tuned column. It has straight sides
> and a sealed end. As such, it sets up oscillation in a linear (line)
> fashion, completely and totally dependent on length, and nothing but length,
> as a direct function of wavelength. While I haven't tested this, I would

That's if you have a very long pipe. For shorter pipes (on
a sound wavelength scale), the ends do matter.

> imagine that pipe diameter would affect sound pressure level, allowing a
> larger mass of air to be vibrated. It may well affect timbre as it deviates

It affects the Q factor.

> Also, some notes on the harp are in the upper bass regions, such as the blow
> 1 on a G, at 196 Hz, with a wavelength around 6 feet. Some are very high,
> like the 3136 Hz high G note on the high G harp, with about 4.6" wavelength.
> A resonant column is 1/4 wavelength, giving us a range of 1.5 feet to about
> one inch. The only one I've seen who could possibly accommodate this as a
> resonant column was E.T. and his telescoping neck, but at last check he
> didn't play the harp.

Remember that humans aren't linear. Have you ever considered
the wavelengths of the sound that a bass singer is generating?
What happens is that the higher harmonics of the bass note
are used to generate the sound and our mind fills in the gaps.
It could be that the higher harmonics of the reed's sound
are amplified rather than the fundamental.

> > from holding, say, a tuning fork vibrating at 440 Hz. over the opening of a
> > resonator with a resonating frequency of 440 Hz. which causes the sound of
> > the tuning fork to thus be amplified. Then again, maybe there's nothing
> > significant about this distinction. I'm unsure.
>
> Good question - but even if it does affect things, I'm not sure it's
> pertinent to the overall question regarding resonance mechanics. It's
> simply another variable. Obviously, it doesn't _hurt_ resonance.

Actually it can affect it slightly. Sounds travels at a
slightly different speed in a flow. In practice, in a pipe
what it gains going in one direction, it loses in the other
so the resonant frequency doesn't change.

> > I'd say probably the harmonica mouthpiece, where the air from the human
> > resonant chamber is applied and interacts with the instrument's vibratory
> > [thus sound wave producing] elements. Still, there remains the issue of
> > the addition of air pressure and flow. Hmmm....
>
> Or being a puckerer, I'd say it's the pucker.

Or maybe neither. Helmholtz resonators aren't the only
resonant cavity/hole/tube yokes.

- --
``It makes me feel all mid-Victorian'' (Fats Waller)
Michael Carley, Mech. Eng., TCD, IRELAND. m.carl~eoleo.mme.tcd.ie
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