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[Physltest] [Phys-L] Re: 'Seeing' frequencies above 30-40Hz (fwd)



An old time demo that was fairly simple. A card is held against a
toothed wheel that is rotating. The faster the rotation, the higher the
pitch. While this is not realy "seeing" the vibration, there is a
reasonable tactile link that a fifth grader might appreciate.
Glenn Malin
University HS
Irvine, CA

lucas@LUCAS.PHY.OHIOU.EDU 1/12/2005 10:05:24 AM >>>

Hi,

I'm working with a group designing a workshop in Ohio for 5th
grade science teachers. The workshop is being designed to work on
material
in the 5th grade indicators for science, one of which is:

"Describe that changing the rate of vibration can vary the pitch of a
sound."

One can treat that as something you just tell them. One can
also
use electronic means measure or produce a given frequency. I'd prefer
to
have some sort of low tech (low budgt) exercise that lets the kids
experience this.

The teachers in the group were talking about a vibrating ruler
giving off sound, as well as one of the resonance tubes that gives
higher
pitch when you whirl it around your head.

In the first, I have the problem that we're not necessarily
going
to 'see' a rate much above 20-40Hz. On the flip side, we're not going
to
hear a rate much below 20Hz. 'Seeing' also includes the problem of the
stroboscopic effect of fluorescent lights.

In the second case, the frequency of the sound is not the same
as
the frequency of rotation since this is a resonance effect. To explain
this right gets a little above a 5th graders head.

Does anyone have a low-budget activity in which one can
experience
the relationship between rate of vibration and pitch?

Thanks!
Mark Lucas

----------------------------------------------------------------------------
Mark Lucas email:
lucasm@ohiou.edu
252D Clippinger Lab phone: (740)597-2984
Department of Physics and Astronomy fax: (740)593-0433
Ohio University
Athens, OH 45701
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