No doubt you have at least heard of it. The opera singer belts out a note and, all of a sudden, people find their tuxedos and dresses soiled by the champagne that just spilled out of their broke glasses. Yes, it can be done. But the question is how. What elements is it in a human voice that is capable of accomplishing this feat?
Disclaimer: Although I am giving you information on how to break a wine glass with your voice, your safety is your responsibility. I take no responsibility for any damage you do to your property or yourself.
The Key is
Have you ever tried (and this you CAN try at home, in fact I encourage you to) wetting your finger and then running it over the rim of a wine glass to here the note it created? Kind of cool huh? This note is the key (no pun intended). As you probably know all sound consists of vibrations that hit our ears and are then interpreted by the brain as some sort noise. Well it also works in the opposite way. Just as something vibrating produces sound, sound hitting something produces vibrations.
Remember that note we produced from the wineglass? Well this is the point where that becomes important. The note that we produced is called a fundamental frequency. It is the frequency at which the wine glass most efficiently turns energy into sound. Naturally, there is a lot more going on (see this blog for information on that), but that is the basic idea. Now if an object is hit with sound waves at its fundamental frequency, it will begin to vibrate along with the sound.
As the note gets closer and closer to that frequency, the glass will vibrate more and more intensely. Increase in volume will also cause the glass to vibrate with more force. Eventually the glass will, quite literally, shake itself apart. Depending on the loudness and the accuracy of the voice, it may just crack, lose a chunk, or shatter. However it can quite awesome.
That being said the chances that you will go to a fancy concert and come back with a ruined suit or dress are rather minimal. This will only work under specific circumstances. First off, the singer has to be on exactly the right pitch for a relatively lengthy amount of time. Secondly, the singer has to have enough volume in order for a glass to break. The videos that I have linked to thus far have both been examples were the singers mouth was only inches away from the glass. By the time the voice of a singer gets to you, it wont be loud enough to cause problems.
So rest easy. But know that it can be done.