Most people have heard tales of how an opera singer can shatter a glass if they hit the right note, but is any opera singer’s voice really so powerful?
Scientists have been carrying out research to investigate whether it’s a fact or fiction – and the results may surprise you! The power of noise is pretty spectacular and the laws of physics suggest that a human voice should be able to shatter glass.
Despite countless comedy shows and cartoons depicting a very loud opera singer shattering a whole row of glasses when they hit top C, it appears to be just a myth. Even though, in theory, it should work, nothing has ever been proven.
© Garrincha / Adobe Stock
Why should it work?
Glass has a natural resonant frequency. This refers to the speed at which it vibrates if it’s knocked or disturbed by a stimulus like a sound wave. Every material on earth has a resonant frequency, but because glass wine goblets have a hollow, tubular shape, they are particularly resonant. This is why they make a melodic ringing sound when they are clinked.
It follows that if someone sings the same tone as the ringing note, then the sound of their voice will vibrate the air molecules around the glass at the resonant frequency. Traditionally, the note is depicted as being a high C.
In reality, it can be any note that causes the glass to start vibrating. If that note is sung loudly enough, then the glass will vibrate and can suddenly shatter into pieces.
During a study carried out at Columbia University in the United States, mechanical engineer Jeffrey Kysar pointed out there was no guarantee the glass would break. He suggested that for an opera singer to be able to break a glass, it would have to have microscopic defects in the first place. These would then buckle under pressure. In fact, every glass has invisible cracks and minuscule defects on the surface.
Even wine glasses that look the same to the naked eye can differ dramatically. Their varying fracture strengths mean some can withstand a higher level of volume than others. The volume of the sound relates directly to the amount of air molecules it displaces.
In simple terms, the sound passes from molecule to molecule, eventually hitting the glass. As the person sings louder, he or she is pushing the air towards the glass harder, but it still won’t necessarily break!
It’s something of a game of chance, as the singer must try to sing a note that exactly matches the resonant frequency of the glass.
Has anyone proved the theory?
The physics is all well and good, but has it ever been put into practice? In history, there have been unsubstantiated reports of singers smashing glasses. The famous opera singer, Enrico Caruso, born in 1873 in Italy, reportedly could shatter a glass with his voice, but there was no proof.
In the 1970s, an advert showed Ella Fitzgerald smashing a glass with her voice – but it was amplified to louder than 100 decibels through Memorex speakers. Most people could shatter only the finest crystal with their voice without it being amplified.
However, if the voice was as loud as an explosion, for example, the singer wouldn’t need to hit the resonant frequency to break the glass, as it would shatter anyway, due to the sheer volume of the sound.
Rock ‘n’ roll
Despite all the theories and rumours of glass-breaking, there was no proof that it could actually be done until 2005. A factual show called Myth Busters on the Discovery Channel tackled the challenge, recruiting Jamie Vendera, a vocal coach and rock singer, to try to shatter some crystal with his voice.
Vendera attempted to shatter 12 wine glasses before he finally struck lucky and broke one glass. This was the first time proof had been captured on film that a voice without artificial amplification could break a glass.
His voice was registered at 105 decibels. Not many singers have the power to sing at this volume! An opera singer who has trained for years can sometimes produce a sustained note of 100 decibels, but it isn’t easy.
So, to the question, “Can an opera singer break a glass?” the answer is yes, but the conditions have to be exactly right to harness the power of noise.
If you lived next door to the source of a noise loud enough to shatter glass, it wouldn’t be a happy existence.
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