I tell my students to whack the tuning forks on their kneecaps. For a clean
fundamental, I prefer the kneecap or heel of the hand. Sharp and quick, but
not particularly forceful, blows work well. With the tuning forks in our
lab, I find that the excitation of overtones is more likely to occur when
the force of the blow is strong. Elbows are too hard, and there's a
significant risk of hitting the funny bone. This is definitely NOT funny
when it happens! If you prefer an actual tuning fork hammer, a medium-sized
one-hole rubber stopper on a dowel rod or pencil works well. We have some
soft rubber hammers that came with the forks, but they're too soft.
Sometimes you can purchase a hard rubber "striking block." This item
resembles a miniature version of the concrete lane dividers that you find
around highway construction sites. The block sits on the table and you hit
it with the tuning fork...handy for one-handed excitation. If you want
overtones, flicking the fork with fingernail works well. Usually I can hear
the overtone right away, before seeing it on the computer. Hitting the
tuning fork extra-hard, or at an angle, or with the dowel stick handle of
the hammer, produces overtones. A tuning fork should not be activated by
banging it on hard surfaces (like table edges), because this potentially
dents, bends, or otherwise damages the fork sufficiently to change its
fundamental frequency.
Vickie Frohne
-----Original Message-----
From: Kilmer, Skip [mailto:kilmers@GREENHILL.ORG]
Sent: Friday, April 11, 2003 11:23 AM
To: PHYS-L@lists.nau.edu
Subject: Re: Tuning Forks
I have my students bang it on their heads. The hardness (of the surfa=
ce and of the blow) is about right.
skip
-----Original Message-----
=46rom: Edmiston, Mike [mailto:edmiston@BLUFFTON.EDU]
Sent: Friday, April 11, 2003 11:16
To: PHYS-L@lists.nau.edu
Subject: Re: Tuning Forks
To reduce the excitation of higher harmonics, and to get good excitat=
ion
of the desired harmonic...
1) Hit it with a hard-rubber mallet (like doctors use for reflexes)
rather than something really hard like plastic or metal.
2) Don't hit it on the end, but hit it about 1/3 of the way toward th=
e
open end from the bottom of the U.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton College
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu