Some companies (e.g. Pasco) make equipment that can demonstrate this. It
consists of a wire (metallic guitar string) stretched across two bridges,
with variable tension, and an electromagnetic pickup. However, the
equipment functions essentially the same as an electric guitar. If you
have, or a student has, a guitar with electric pick-up, you can feed that
signal into an oscilloscope. The first obvious thing to notice is the wave
is periodic, but not a pure sinusoid... indicating it is a composite of
several harmonic waves. Furthermore, you can pluck the string at various
places and see the waveshape change. Plucking at the center favors the
first harmonic (fundamental) and also other odd harmonics. Plucking at
one-fourth the length favors the second harmonic. Plucking near the bridge
will put energy into many harmonics. This is detected both by the
oscilloscope pattern and also the timbre (tone quality).
FT analysis is also nice if you can easily do it... but it certainly is not
necessary.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817