How sound waves can break glass

There is something about a singer shattering glass that reminds us of our childhood. How many cartoons have we seen that features an oversized opera singer wearing a horned helmet belting out a note so loud and irritatingly high-pitched that glass shatters everywhere — from windows to cups to glasses?

We never considered the validity of these cartoon images. Were these images based on fact or just a funny gag for the audience?

Thankfully, there are inquisitive people in this world to find the answer! Television show “Mythbusters” and the magazine “Scientific American” delved into this issue and we were intrigued by their results.

It turns out Bugs Bunny was right; the human voice can shatter glass, with or without the horned helmet. However, this feat is not as easy as it appears.

First, not all types of glass can be shattered by the human voice. Fine lead crystal wine goblets are ideal due to its “hollow, tubular shape,” and the fragileness of the crystal, according to Scientific American. Then you need to find the glass’s resonating frequency, or vibrations. This can be found out by simply flicking the glass with the fingertip and listening to the ringing sound produced from it. Put your mouth close to the glass and try to match its pitch. Be prepared to sing loud. Your best shot at shattering glass occurs at 100 decibels — by comparison, normal conversation is 50 decibels.

For those of you who test this experiment, good luck!

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