Yes. it is possible. It has to do with resonance. Lightly strike the glass and it will ring. That tone is it's natural frequency. If you then make a tone that is at that same frequency, the glass will vibrate as well. If the tone you make is loud enough, then the vibration will cause the glass to flex more than the strength of the glass can withstand and the glass shatters. In response to incognito, The the changing of the opera singer's voice in your example is him/her hunting for the right pitch. In this respect your answer is correct. However, you will note that when actually trying to break a glass, the singer's voice is always loud. They do not sing softly because a soft voice does not have the energy to induce oscillations of sufficient amplitude to break the glass. So, I stand by my answer. The sound must also be loud not just of the right frequency. Edited to correct typos.

"...one you make is loud enough..." Well, actually, the way it goes is like this. True that the glass has a natural frequency of its own. When a person (like an opera singer) gives out a shrill voice...it has its own frequency, for each 'level' of pitch. You might have noticed that the person make their voice shriller and shriller and then at one point the glass breaks. Note that the voice becomes shriller (its frequency increases) and not louder (wherein the amplitude of the wave would increase). What happens is that the frequency of the person's voice increases, and at one point it reaches the natural frequency of the glass. Now what resonance says is basically that if a frequency equal to the natural frequency of a body is induced upon it, then it begins to oscillate, relatively more vigorously (with a greater amplitude). So when a voice frequency reaches the natural frequency of the glass....the glass experiences that vigorous oscillation and eventually gives in (because of the crystalline structure of the glass). Some examples where the resonant body doesnt break would be the (classic) example of a bridge resonating with the boot sounds of marching soldiers. Thats why they are told to 'break' their steps when they walk on bridges (to prevent resonance)!

I was watching Mythbusters recently and they set out to confirm or bust this myth. Well, they confirmed it. First, they shattered a lead crystal glass by setting it in front of a speaker, that had a piece of plywwod in front of it with a big hold drilled in it. The glass shattered. Next, they wanted to see if it could be done with just the human voice and without amplification. Finally after about a dozen attempts, this guy shattered the glass with his voice and no amplification. As far as they could tell, it was the first time it had ever been captured on film. I'm not an engineer but I think they said he had achieved 52 Hz and 120 decibles. It was really neat to watch.

It most definately can be done. Here are some sites with some good info. http://www.acoustics.salford.ac.uk/acoustics_world/glass/glass.htm http://www.physics.ucla.edu/demoweb/demomanual/acoustics/effects_of_sound/breaking_glass_with_sound.html http://www.physlink.com/Education/AskExperts/ae232.cfm

Yes it has been proven on mythbusters. http://video.google.com/videoplay?docid=-7765557442856739526&q=MythBusters+glass&total=30&start=0&num=10&so=0&type=search&plindex=2

Yep, that one guy from Man-O-War did it on Mythbusters.

Yup, I saw it on Mythbusters too. I love that show.

yes because if the force of the vibration is large enough the size of the vibration will become large enough to break the glass.

Indeed it can.

It is possible. I have done it. The thing is,it could be the lowest note imaginable, and the glass could still break--IF--AND ONLY IF--that note is the EXACT pitch of the glass. There you have it.

High frequency sound waves can shatter glass if powerful enough. This happens because the glass vibrates at the same frequency as the sound waves on the outer surface of the glass, but at lower frequencies inside the glass. This causes interference in the waveforms moving through the glass, which stress the glass, causing it to break. This is a different effect than when a single sharp sound, such as an explosion, pushes the glass beyond its breaking point.