Name: Julia E. R.
Date: Saturday, April 20, 2002 8:17:44 PM
We are doing a community TV show on Sound. It is a
live, call-in show geared toward 4th and 5th graders, but with
respondents K-8th grades. We are covering vibration (sound is results
when matter is vibrated), pitch, loudness, and waves (a wonderful physics
teacher from ETHS is joining us with his wave machine.)
I need some whiz bang, keep their attention, experiments with sound.
Perhaps including instruments. Thanks!
One possible experiment might involve something such as a guitar. If the
string is plucked, a pitch with a wavelength of twice the string length will
result. It will not be a pure wave. It will have many harmonics, twice the
pitch, three times it, four times and so on will exist. Placing a
knife-edge firmly at the halfway point will not eliminate the sound. You
will get a much quieter sound with a pitch exactly one octave higher: half
the wavelength and twice the frequency. Placing the knife-edge 1/4 of the
way from either end will result in a 2 octave increase: 1/4 of the
wavelength and 4 times the frequency. Anyone who knows how to play a guitar
can point out these locations on the neck of the instrument. He/she may
even know the locations without understanding why they work as they do.
Dr. Ken Mellendorf
Illinois Central College
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