Can Opera Singers Break Glass With Their Voice?

If you're old enough, you may remember from a commercial from the '70s in which singer Ella Fitzgerald broke a wine glass by singing. Technically, the ad showed how a recording of Fitzgerald's voice broke glass. The commercial was for Memorex cassette tapes, and the idea behind the ad was that the tapes could record with such precision that even a recording of Fitzgerald's voice could break glass (via NPR).

While the commercial showed the recording breaking the glass, Fitzgerald had to prove she had the chops to get the job done. NPR reports that she met with company executives at a hotel in New York where she sang the ending of "How High the Moon." The jazz singer did indeed break the glass, got the job, and became a spokesperson for Memorex. Her voice was most likely amplified to break the glass, but can opera singers actually break glass with just their voices?

Science says it can be done

Science tells us that you absolutely can break a wine glass with your voice, and it all comes down to how sound waves react with other objects. Live Science explains that all objects have what is called a natural frequency. You can hear a wine glass's frequency when you rub your wet finger around the rim. Voices have a natural frequency, too, and they can shift the air molecules around nearby objects. Sound waves close enough to a wine glass can make the glass vibrate, a process called resonance. Enough vibration will result in so much resonance that the glass will eventually break.

But there's more to it. Scientific American explains that the volume of sound is also related to how it displaces air. When a singer sings really loudly, the sound molecules are creating a great deal of resonance. Opera singers train to sing loud, and some of their voices can reach up to 100 decibels, which is about as loud as a bulldozer, according to Bacou-Dalloz Hearing Safety Group. At that point, breaking a delicate glass might be possible.

It's not that easy

While it's possible to break a wine glass with your voice, you have to have a lot of things going for you. Scientific American points out that the state of the glass is an important factor. Jeffrey Kysar, a mechanical engineer at Columbia University, told the publication that even if you could create enough resonance to break a wine glass, that doesn't mean that it will break. That's because breaking glass involves many variables, including the size of the glass and any defects it has. A thin wine glass with slight defects is more likely to break than a thicker one with no defects.

A fine, crystal wine glass is fragile enough that it can be broken at around 100 decibels — especially with amplifiers. In 2005, singer Jamie Vendera broke a wine glass after 12 tries without amplifiers on the television show MythBusters. His voice reached 105 decibels, which is about as loud as a motorcycle, according to Bacou-Dalloz Hearing Safety Group. Needless to say, while it's possible for opera singers to break wine glasses with their voices, it's uncommon.