[:PiraScheme#WavesSound: Table of Waves and Sound Demonstration]

List of Waves and Sound Equipment & Supplies]

[:Demonstrations:Lecture Demonstrations]

Breaking Glass with Sound, 3D40.55




A large 2" compression driver with horn is used with an audio amplifier to break glassware/stemware at its resonant frequency. An adjustable function generator is used to deliver a pure tone. A strobe light can be added to show the oscillations of the glass before it shatters.



ID Number

Apparatus, (Box with Speaker)

WS, Floor Item


WS, Bay A5, Shelf #2

Audio Amp

WS, Bay R-A3, Shelf #2


WS, R-B1, Shelf #2

Agilent 33220A 20MHz Function Generator

WS, Bay R-A3, Shelf #3

Duct Tape

Gray Stock Cabinet

Sound Level Meter

WS, R-A2, Shelf #3

Important Setup Notes:

  1. This demonstration requires a minimum 10 hour notice.

  2. This demonstration requires Stemware

  3. Practice is a must! Every glass is different.

  4. Requires an operator with a good ear for sound

  5. Requires a camera

  6. Slow Motion Video or Camera is Available


  1. Set large box out, visible to audience.
  2. Connect the speaker to an output of the audio amplifier
  3. Connect the function generator to an input on the audio amplifier
  4. Firmly tape the stemware to the steel brick and place in box as close to the speaker as possible.
  5. Make sure that the stemware isn't too high. The top third of the horn should be above the stemware.
  6. Make a paper feather out of a post-it and stick it to the rim of the stemware, so that the paper feather can vibrates at the resonant frequency of the glass.
  7. With the speaker at a vary low volume, rapidly hit the stemware with a tuning fork mallet and adjust the function generator to narrow in on the resonant frequency.
  8. Slide the front cover closed and shim it in place to prevent the cover from vibrating.
  9. Set up a strobe light and or cameras if necessary.

Cautions, Warnings, or Safety Concerns:

  1. Broken Glass is Very Very Sharp....
  2. Sound within the box can reach 140dB.
  3. Glass may not break!
  4. Glass could shatter well you find resonance.
  5. Use duct tape to pick up shards of glass.


Breaking stemware or glassware is more of an art and can be tricky to do. With this equipment and setup. We're able to break most any type of glassware for Pyrex beakers to tall bear schooners. The more lead in the glassware the better it is, but cheep glass that has a nice sound works well. One has to tune the system to the stemware's resonant frequency. This can be done several different ways. My favorite way is to have the speaker at a very low amplitude, box is open, and the stemware firmly in place on the brick. Do quick raps hits on the glass with a tuning fork mallet as you adjust the function generator, 10 Hertz at a time, listing for beets. Listen to the beet frequency to zero in on the resonant frequency of the stemware, ie the beets go away. Much like piano tuners do. This has to be done in the box with the stemware firmly taped to the brick. The stemware's natural resonant frequency shifts lower once it's base is firmly taped to the brick. The stemware is mounted this way so that at high amplitude the glass doesn't vibrate around and generate harmonics, thus loosing energy.

Once tuned, write down the frequency. Make sure the paper feather is in places an curved outward. Zero the sound level meter and place it in the box. Close the front cover and secure it in place. Now the volume or amplitude can be increased, somewhat to see how well the feather vibrates. Readjust the frequency of the function generator to achieve the resonant frequency of the glass - At Low Amplitude, either by sound and/or by one hertz intervals. Watch the feather vibrate. Once resonance is achieved, the paper feather will vibrate violently. You should be set. Turn up the volume on the audio amplifier, ie the amplitude, the glass should shatter. Fine adjustments of the function generator at high amplitude maybe needed to maximize the resonant amplitude of the glass.

Optional: Setup a strobe light with a second function generator. Adjust the frequency fast enough to slow the motion of the feather and glass rim. Do this when the speaker is at low volume.

















Slow Motion Video attachment:GlassBreak.MTS

Speaker/Horn Information:

The Speaker is an 8 Ohm D-408Ti 2" Titanium Horn Driver 4-Bolt, by Selenium Loudspeaker and was $222.00. The horn is a Selenium HL14-50 2" Exponential Horn 45x45 4-Bolt and was $27.00. Extra diaphragms are Selenium RPD-4400Ti Diaphragm For D-408Ti & D-4400Ti horn drivers and are $76.00 each. The Speaker total weight is about 21.25 lbs. The Magnet is about 7" x 1".






Videos of Breaking Glass with Voice

  1. http://www.youtube.com/watch?v=amuPoPkAlx8&feature=player_embedded

  2. http://www.youtube.com/watch?v=sH7XSX10QkM&feature=related

  3. [http://www.youtube.com/watch?v=O9FrMkhQoA4 Myth Busters 1/3]

  4. [http://www.youtube.com/watch?v=nHSGd2X1nc8&feature=related Myth Busters 2/3]

  5. [http://www.youtube.com/watch?v=oXV45t6wlWU&feature=related Myth Busters 3/3]


  1. List any references