Re: Resonance Demo

[Sam Sampere <sampere@SUHEP.PHY.SYR.EDU>]

The box is divided into 3 sections.  Mounted in the center section are 2 - 8"
woofers aimed at opposite ends of the box.  The speakers are wired in parallel,
thus in phase.  There are three holes cut in the top of the box, one above the
speaker section, and one at each end of the box.  This produces low-high-low or
high-low-high pressure above the holes and causes a 24" x 3" piece of
untempered glass to vibrate (f~34 Hz).  Drive it hard enough and it will break.

I just found this info in the PTRA Waves binder.

Sam

Tom Ford wrote:

> This is described in the AAPT/PTRA item called Teaching About Waves and
> Sound 1993, revised 1996 used in PTRA workshops of the same name.
>
> At 01:13 PM 11/11/99 -0800, you wrote:
> > I need help in getting printed plans for making the following resonance
> > demo, which I saw at one of the conferences/workshops I attended in the
> > last two years (I can't remember exactly where or when):
> >
> > The apparatus consists of a wooden box about the size of two shoe boxes
> > laid end-to-end. There is a speaker (possibly two) inside and the box is
> > divided into (3 or 4 ?) chambers. There is an opening or two facing
> > upward. There are two supports on which is placed a piece of (plate) glass
> > (about 2 feet long x 4-6 inches wide). The supports hold the glass about
> > 1-2 inches above the box. As the frequency of the sound is adjusted, a
> > standing wave can clearly be seen to develop in the glass, and at the
> > right frequency the glass shatters.
> >
> > This is more dramatic than the usual approach with speakers and a beaker
> > or wine glass. It is also easier to setup--no microphone and oscilloscope
> > are needed to tune the frequency. The sound does not have to be so loud as
> > to hurt the ears of those in the front row of the class.
> >
> > If you have plans for this (including what kind of glass to use, which
> > is critical) or can refer me to someone who might be able to help, please
> > let me know.
> >
> > Thanks.
> >
> > Mike Ugawa
> > St. Ignatius College Prep, San Francisco
> > mugawa@quark.sfsu.edu
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--
Sam Sampere
Syracuse University
Department of Physics
Syracuse, NY 13244
315-443-5999