Date: Mon Aug 27 18:51:48 2007

Author: Thomas J. Bauer

Subject: Re: Shattering with speaker

Post:
Use a strobe light next to the glass and at a harmonic of the resonance
frequency to see the oscillation in the glass. Tune the function generator
until you get the largest amplitude. Then rotate the glass until you get
the largest amplitude. When you turn up the volume the glass should break.
I've broken all of the glasses others in our department labeled
"unbreakable".

I use a medium quality wine glass from Kitchen Etc. Pick ones with a nice
Q. We also use a TV camera so that students can see how much the glass
oscillates before it breaks.

Tom bauer
Wellesley College


tap-l@lists.ncsu.edu on Monday, August 27, 2007 at 5:21 PM -0500 wrote:
>While I'm at it, may I ask specifically about the geometry of
>everyone's speaker-breaking-a-wine-glass setup? Mine's got the
>speaker mounted vertically, on a piece of 1/2" plywood with a 2"
>diameter hole to direct the sound "beam". I drive the horn with a 60
>watt PA amplifier. All this is enclosed in a 1/2" ply box (one side
>plexi) with fiberglass insulation mounted on the walls. I simply
>knock the glass ahead of time and listen for the resonant pitch, then
>try to match it on the function generator before putting the glass
>into the box. (In other words, I'm not monitoring the resonance of
>the glass in real time.)
>
>The speaker is getting quite loud, but I haven't been able to break
>anything, including many varieties of dollar-store rosebud glasses and
>the like.
>
>Any input would be of much help.
>
>Thanks again,
>
>David




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