Breaking Glass With Sound

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Just looking for advice on my page drewt0657 drewt0657 1 56 Dec 17, 2009 by pasquinit pasquinit
Halfway Point pasquinit pasquinit 4 67 Dec 16, 2009 by pasquinit pasquinit
Tacoma Narrows Bridge alex_latham alex_latham 0 120 Dec 6, 2009 by alex_latham alex_latham

Guiding Question

What do you want to know?
I want to know at what frequency and decibel range glass will break.


What do you expect to observe?
I expect to observe that glass (wine glass) will break at a specific frequency and decibel range. I figure that the sound will have to be amplified in order for the glass to break; I will take that into consideration. I feel that I am going to not run into any troubles, but i possibly could. I feel that this experiment is pretty well known and if I have any troubles I will just do some more research.

Experimental Procedure

How will you know whether your prediction is correct?
I will know that my prediction is correct when the glass breaks. Whether that be at my specific frequency/decibel range or if it breaks at another frequency/decibel range. If the glass doesn't break then the


1. wine glass
2. decibel meter
3. tone from xplorer GLX
4. microphone to measure the frequency using LoggerPro and an FFT graph
5. camera to watch how glass moves when put in those conditions
6. speakers
7. light


1. First, I took the wine glass and hit it with a metal knife to produce a tone; I then recorded the tone using the microphone and LoggerPro to find the highest frequency of that certain glass. The reason I wanted to find the highest frequency of the wine glass is because this is frequency that when blasted at a high enough volume will break the glass.
2. I used the xplorer GLX to produce the frequency I had just found from hitting the glass with the knife. I then turned the volume up on the computer speakers I was using all the way up and recorded the way the glass was moving because of the certain frequency.
3. After I took the certain frequency and blasted it toward the wine glass I made some observations about how the glass was acting. The glass seemed to want to break at this frequency but my speakers did not have enough power to break the glass. The glass, after i blasted the tone at it contorted, vibrated and made the straw I had placed in the glass to move around.
4. As all this was going on I was recording how the glass was reacting using a high speed camera.
5. I stopped recording and producing the tone after many attempts to break the glass with unfortunate outcomes. I did even test the frequency of the glass again by hitting it with knife and recording the frequency using LoggerPro, but no luck.
Below are some pictures of my setup for the experiment and the FFT graph showing the highest frequency of the glass (frequency used to break glass)


Some observations of the glass while the resonance frequency was blasted at the glass would include that the glass contorted and moved in and out. The glass vibrated very wild and almost broke; from the glass vibrating the straw moved all around. I knew that I was close to almost breaking the glass because the glass sung after the tone was stopped being blasted towards the glass. I believe the only reason the it didn't break was because I was off only by a couple of Hz. The wine glass rim is actual moving back and forth, which is why you get the vibrating feel. The rim is actually moving back and forth at the same frequency as the sound is hitting it, 476.1Hz. The way the sound waves break the glass is that they leave speaker travel through the glass and bounce back just as another wave is hitting the glass, this is why it breaks. Here is a link to show what I mean: Glass breaking with sound waves entering (2:09 into movie) Here is another link showing what a straw looks like in the glass when the sound is blasted towards it: Straw Moving (1:14 into movie)


What was the result of your investigation?
The result of my investigation was that my because my speakers were not strong enough to amplify the tone I was unable to break the glass. The frequency of the wine glass that I used, I found to be 476.1 Hz and the decibel range for what my speakers could produce was right around 100 decibels.


What new questions have you raised? Why is your result important?
I found that without strong enough speakers and an amplifier the glass could not be broken. I did try later at a friends house to use his large speakers and amplifier to break the glass but was still unable to do so. I believe that the reason the glass did not break was because the frequency for that particular was off by a couple Hz. I did try to change the frequency up and down but still could not break the glass. So, I believe that in order to break glass with sound you need to have amplified sound and the frequency for that particular glass needs to be exact.



Thank the people who have helped you complete this exploration.
I would like to thank Dr. P for letting me borrow some materials to do perform and examine this experiment. I would like to thank my mom for helping with the setup of this experiment and I would also like to thank Ben Wilson for letting me try to break the glass with his speakers/amplifier and for enduring that extremely loud and annoying sound.

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