breaking a glass with sound

[eyedea]

I’m doing a science project in which I would like to prove that one can affect objects with sound with out ever physically touching the object. Now, I would like to go as far as breaking a glass, but I don’t necessarily mind less. I already have a sine wave generator on my computer, but I read that I would need the sound to be as loud as 130 decibals? Maybe somebody can give me other ideas, or just some tips, or anything. thank you

[Joe_Random]

Try using the sine wave generator to cause a tuning fork to resonate. That’ll be much easier to do, since they’re designed to produce a single pitch.

[sailor]

You can make the several strings of a stringed instrument resonate.

You can also create a standing wave and show how fine sand or filings will concentrate in the nodes.

[Boyo_Jim]

You can plug the output of your computer into a big honkin’ amplifier with a big honkin’ speaker. If you have a powerful home theater, and your neighbors are distant, deaf, or dead, it might work for you.

[Zenster]

Unless your computer has a whole mess of heatsinks in back or a fan cage the size of your monitor, it won’t drive diddle in terms of breaking more than a microscope cover slip.

You’re asking about resonant harmonics and sympathetic vibration. That usually requires many more Watts than your computer’s soundcard is going to pump on a good day.

[Rabid_Squirrel]

Wait a sec.

I thought is was impossible to get soda (common) glass to shatter from sympathetic vibration since it’s a amphomorphic (sp? a solid without an ordered crystaline structure) compound. If you’re talking about lead crystal glasses, then it’s possible.

Just noticed no one else pointed it out - sorry if I sounded condecending.

[Bob55]

*Originally posted by eyedea *
I’m doing a science project in which I would like to prove that one can affect objects with sound with out ever physically touching the object.

Why aren’t sound waves considered ‘touching’ - I’m just curious as to what the actual definition is. The waves compress air molecules which vibrate the glass…it’s like shooting a spit ball through a straw - I never actually touched it but it still flew across the room by using air molecules to do my bidding.

[trabi]

Breaking glass with sound

[NoCoolUserName]

Depending on how carried away you want to get…hang a curtain of some light material (silk is best but it’s expensive). Get a big honkin’ woofer (15" or 18") especially if you can find one in a folded-horn cabinet. Put a 200 watt amp or larger between your computer line out and the speaker cabinet with the curtain hanging in front of the cabinet. Crank it up and watch that puppy shake!

[bibliophage]

Cecil Adams on Can opera singers shatter glass with their high notes?

they go out and get a drinking glass with high lead content, tunk it with a rubber mallet to make it ring, then read the frequency on an analyzer. Then they get a singer to sing the same note (typically F above middle C), amplify it to maybe 92, 94 decibels, and with luck you get glass shrapnellini. Memorex technicians using a strobe have found that prior to the break the sound causes the rim of the glass to deflect as much as a quarter inch.
…
Admittedly 90-plus decibels is pretty damn loud, but one of the reasons the Memtek folks crank it up that much is that they’re using an inexpensive ($7) glass rather than fine crystal, which is more fragile.

[sailor]

*Originally posted by Rabid_Squirrel *
Wait a sec.

I thought is was impossible to get soda (common) glass to shatter from sympathetic vibration since it’s a amphomorphic (sp? a solid without an ordered crystaline structure) compound. If you’re talking about lead crystal glasses, then it’s possible.

Just noticed no one else pointed it out - sorry if I sounded condecending.

I believe you are mistaken. The way it works is to use a sound with the same natural resonating frequency as the glass. You tap the glas, listen to the frequency and then excite it with the same frequency.

[bbeaty]

Physics teachers use cheap wine glasses for their “glass break” demonsration. You have to get the right kind: ones with high “Q” which ring for a long time when tapped. Also, a normal loudspeaker won’t do it. Get an outdoor horn-type speaker, then remove the horn, leaving just the driver with it’s one-inch outlet hole.

[Rabid_Squirrel]

Sailor:
My arguement was that the resonance frequency of a soda lime glass (the type you commonly get in bottles and cheap glasses, the ones that go “thunk” when you hit it) isn’t a pure frequency, but a mixture of tones since the there isn’t an ordered crystalline structure (cite). Even if you did tap the (soda lime) glass and played it back, then the non-uniform crystalline structure would stop any resonance occuring on playback. You could crack soda lime glass with sound, but that would be driven purely by pressure differentials NOT resonance. (cite)

Sometimes on television a high pitched noise breaks the windows in a house. I know that tubular objects such as wine glasses will break when the frequency corresponds to the natural frequencies of the glass, but does flat sheet glass such as windows experience this same effect? – RF, Jackson, Michigan

In real life, only explosive sounds will break normal glass. That’s because normal glass vibrates poorly and has no strong natural frequencies. You can see this by tapping a glass window or cup–all you hear is a dull “thunk” sound.

For an object to vibrate strongly in response to a tone, that object must exhibit a strong natural resonance and the tone’s pitch must be perfectly matched to the frequency of that resonance. A crystal wineglass vibrates well and emits a clear tone when you tap it. If you listen to the pitch of that tone and then sing it loudly, you can make the wineglass vibrate. A crystal windowpane would also have natural resonances and would vibrate in response to the right tones. But it would take very loud sound at exactly the right pitch to break this windowpane. An unamplified human voice can’t break a crystal wineglass and it wouldn’t be able to break the crystal windowpane either.

This is backed up by bbeaty’s statement that

You have to get the right kind: ones with high “Q” which ring for a long time when tapped.

which is a perfectly good description of lead crystal - not soda lime glass.

I stand behind my original post.