Physics suggests that a voice should be able to break glass. Every piece of glass has a natural resonant frequency—the speed at which it will vibrate if bumped or otherwise disturbed by some stimulus, such as a sound wave—as does every other material on Earth. Glass wine goblets are especially resonant because of their hollow tubular shape, which is why they make a pleasant ringing sound when clinked. If a person sings the same tone as that ringing note—a high C in legend but in reality the matching pitch could be any note—the sound of her voice will vibrate the air molecules around the glass at its resonant frequency, causing the glass to start vibrating as well. And if she sings loudly enough, the glass will vibrate itself to smithereens.
In 2005 the Discovery Channel television show MythBusters tackled the question, recruiting rock singer and vocal coach Jamie Vendera to hit some crystal ware with his best shot. He tried 12 wine glasses before stumbling on the lucky one that splintered at the blast of his mighty pipes. For the first time, proof that an unassisted voice can indeed shatter glass was captured on video (see above).
Vendera's glass-breaking wail registered at 105 decibels—almost as loud as a jackhammer. Not many people can muster the lung power for that kind of noise. Opera singers train for years to build up the strength to produce sustained notes at volumes above 100 decibels. (By comparison, typical speech is around 50 decibels.)
Source: Scientific American
Tags: Opera | Singer | Shatter Glass | Glass | Singing