How can you get a sound wave to break a glass?

Q: Can we break a glass using sound?

To smash a glass, youll need to blast it with upwards of 100 decibels of sound, which is roughly equivalent to a lawn mower.

Q: Can loud sounds cause glass to break?

If the resonant frequency of the singers voice is loud and steady enough, it could cause the glass to break once the vibrations of the glass build up past its elasticity limit, causing it to fail.

We’ve all heard about opera singers breaking a glass using voice but how does sound break glass and is it really possible at all?

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Can we break a glass using sound?
Can loud sounds cause glass to break?
What sound frequency will break glass?

The answer is that an empty wine glass can be broken by sound alone if the sound is at the right frequency and volume.

The following is a brief explanation of how sound breaks glass. Don't try this at home!

A glass has a natural resonance. Resonance is the natural frequency at which the glass will readily vibrate. To find the resonance of the glass, ping the glass and listen to the sound. That is the correct frequency (or tone) for the glass to start to vibrate.

The glass itself must not be affected by damping. Damping is interference with a force which will act to prevent the glass from vibrating. Embossed glasses should be avoided. Lead in lead crystal may provide damping although otherwise the glass is very pure. The glass should be empty.

A wine glass is a good shape because it stands on a stem. This reduces the amount of damping that could be caused by a glass sitting directly on a surface such as a pint glass. The walls of the glass should be as thin as possible.

Making the same tone as the natural frequency of the glass will induce vibration in the glass. However, the note alone is not the only factor - volume is also important. The louder the sound, the more violent the vibrations will be. When they reach a level that the glass cannot withstand it will shatter.

The volume required is more than 100 db, a level that is difficult but not impossible to reach with just the voice. Normal speech is around 50 db. In experiments, often an amplifier and speaker are used so achieve the required volume.

This works even better if the sound is concentrated on one area by putting the glass behind a wooden screen containing a hole. The sound is directed through this hole and on to the glass. Research has been carried out which shows that the glass needs to contain a small flaw. The shattering starts with this small crack. The blemish can be too small to be seen by the naked eye. Good quality glasses with no flaws are unlikely to break.

Opera singers have been rumoured to break glass with just their singing note. They have been trained to produce more than 100 db of volume and would have good pitch to match the resonance of the glass.

More recently, rock singer Jamie Vendera has been filmed successfully breaking a wine glass using just his voice. To do this, he directs the sound on a concentrated area of the glass very close to his mouth. To help him check he has the right frequency, he places a straw in the glass. When it starts to vibrate he knows he is close.

Hope this answers the question "How does sound break glass?".

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How does sound break glass?

Asked by: Grace Jackson

Answer

While breaking glass with sound is an interesting trick, it really takes a lot of effort to get the job done. First off, the glass in question needs to be crystal, not just any glass. Crystal, resonates all at one particular harmonic frequency. Try getting a crystal wineglass, dipping your finger in water, and rubbing it gently around the rim of the glass. Your finger will vibrate on the glass, and once you get it right and consistent, the glass will 'hum'.

Waves of any sort set up sympathetic vibrations in the materials they impinge upon, which is the principle behind many many things, including telephones and radar. The glass hums (and doesn't shatter) because the amplitude of the waves (the actual physical displacement that creates the sound) is not sufficient to surpass the strength of the glass. If you generate a sound that is the same frequency the glass resonates at, after you turn off the sound, the glass will hum a little, much like a pitchfork. To break the glass, you need to broadcast not only a sound that is *just* the right frequency, but also has a high enough amplitude (loudness) to exceed the strength of the glass to resist those vibrations. When the sound gets too loud for the glass to vibrate, it shatters the glass. I HIGHLY recommend asking a teacher about this, since doing experiments with crystalware at home is not likely to win much support whoever owns the crystal.

Further reading: Breaking a Wine Glass With Sound

Answered by: Frank DiBonaventuro, B.S., Air Force officer, Tinker AFB, OK.

Any physical object has frequencies at which they naturally vibrate, known as resonance frequencies. If you flick a crystal wine glass with your finger, you will hear a fairly clear tone as the glass vibrates, causing waves of air pressure to emanate out from it, which your ears and brain interpret as sound. The sound gradually gets quitter and dies out as the amplitude of the vibrations diminishes due to energy being carried away by the sound waves.

Your voice is also a series of air pressure waves, with the pitch related to the frequency of the waves, and the volume related to the amplitude of the waves.

Now to fit these two together. If you can match the pitch of your voice to the resonant frequency of the glass the vibrating air will start the glass vibrating too. If you can do this with sufficient volume, the glass will try to move in its vibration farther and faster than the material in the glass is able to move, and the glass will break under the strain.

This is an example of a driven oscillation. Imagine pushing a friend on a swing: after one big push, the swing slows down, but continues oscillating for a while with a given frequency. If you impart randomly timed pushes to your friend, you are unlikely to get her moving very much. But if you carefully time your efforts so you administer a small push at the same time in each cycle, your efforts can add up and your friends amplitude (height) will increase a bit each time. Likewise, the sound of your voice administers hundreds of tiny 'pushes' each second to everything around you. If the timing is right, the energy of the pushes can add up, leading to a large stress on the glass.
Answered by: Rob Landolfi, Science Teacher, Washington, DC

Can we break a glass using sound?

To smash a glass, you'll need to blast it with upwards of 100 decibels of sound, which is roughly equivalent to a lawn mower.

Can loud sounds cause glass to break?

If the resonant frequency of the singer's voice is loud and steady enough, it could cause the glass to break once the vibrations of the glass build up past its elasticity limit, causing it to fail.

What sound frequency will break glass?

First, to shatter glass, the frequency of waves should be around 550 Hertz. Therefore, the person in charge of shattering the glass has to make sure that their voice can attain a frequency in that range. Another important factor is the loudness or intensity of the sound wave.