Date: Sat, 12 Oct 2002 20:25:55 -0400

Author: "Dick Heckathorn"

Subject: RE: breaking a glass with a speaker

Post:

Greetings,

I saw the frequency matching done by supporting the wine glass
horizontally. A dime was placed in the beaker which danced at the
resonance frequency. The matching was done at a medium intensity. Then
the intensity was increased to maximum and it broke.

Dick

"Science is nothing more than learning how to communicate with nature in
such a manner that it will talk back."

Helping teachers who facilitate, motivating students who learn.
Dick Heckathorn 14665 Pawnee Trail Middleburg Hts, OH 44130
440-826-0834
Physics Teacher CVCA 4687 Wyoga Rd Cuyahoga Falls, OH 44224
330-929-0575 VM 120


-----Original Message-----
From: owner-tap-l@listproc.appstate.edu
[mailto:owner-tap-l@listproc.appstate.edu] On Behalf Of Richard Berg
Sent: Friday, October 11, 2002 12:24 PM
To: tap-l@listproc.appstate.edu
Subject: Re: breaking a glass with a speaker

Erik,

You are going to get a large number of responses to this one.

If I understand what you are doing, I think it will not work.

First of all, use a cheap beaker or a wine glass with a nice ring.

You should put a microphone close to the glass, and display the signal
from the microphone on a scope while you trigger with the signal from
the
wave generator. Use a very stable oscillator and a healthy horn driver
with an amplifier having around 25 Watts or more output.

Match the pitch of the oscillator to the pitch that you get by tapping
the
brim of the beaker or wine glass, then tune very carefully until you get
a
large increase in amplitude and a phase shift of the signal from the mic
as you pass through the resonant frequency. This must be done VERY
CAREFULLY. At this point you should be able to see the vibrations of
the
beaker brim with a strobe after you have turned out the room lights.

Use a hearing protector muff. I think care in the setup will minimize
the
noise and discomfort.

You can see ours at:

http://www.physics.umd.edu/lecdem/services/demos/demosh3/h3-61.htm

Best wishes,

Dick Berg



On Fri, 11 Oct 2002 erikh@email.arizona.edu wrote:

> Hello everybody, I'm new to the listserv but you might remember me
from Boise--the
> red-headed guy from the University of Arizona.
>
> Anyway, I want to show my students what they've all seen on TV--that
you
> can break a glass with sound energy.
>
> I tried it on my own & it didn't work by just matching the pitch with
a frequency
> generator, turning it up 'till I couldn't take anymore, then fine
tuning
> it in both directions.
>
> Where am I going wrong? glass thickness? more power? finer tuned
frequency?
> 'Focusing' the sound somehow?
>
> As it was, I could smell my speaker beginning to burn afterwards.
>
> Also, has anybody ever been able to do this with just a mic, amp, &
speaker
> so that it creates a feedback loop?
>
> Erik Herman
>
>

***********************************************************************
Dr. Richard E. Berg, Director Phone: (301) 405-5994
Lecture-Demonstration Facility FAX: (301) 314-9525
Department of Physics e-mail reberg@physics.umd.edu
University of Maryland www.physics.umd.edu/lecdem
College Park, MD 20742-4111
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Eschew obfuscation.
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