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A MAKE reader named James wrote to us with a physics question. It’s in reference to the video above:

First of all, I wanted to say that you guys have the BEST vids on youTube!

I have started to read quite a bit about frequencies and I want to do this experiment.

If you watch the video, he breaks a glass using a signal generator and an oscilloscope.

The question I have is where you get the mic that hooks up to the oscilloscope and what is that bronze colored cylinder on right of the attached pic?

Obviously it emits and focuses the waves from the signal generator at the glass, but I cannot see this thing for sale online. Probably because I don’t know what it’s name is.

If you could help point me in the right direction so I can get the equipment and do the experiment, I would be very happy!

If you can help James, please post it in the comments section!

Mark Frauenfelder

Mark Frauenfelder is the editor-in-chief of Make magazine, and the founder of the popular Boing Boing blog.


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Comments

  1. Anonymous says:

    Hmm…a transducer is used for converting the sound wave into an electrical signal that can be used by the oscilloscope. The bronze cylinder is known as a waveguide, and, although they are most commonly used for electromagnetics, I’m sure you could repurpose it to focus sound waves.

  2. Peter Barvoets says:

    Looks like he’s using a McIntosh C22 pre-amplifier and a McIntosh MC75 mono 75 Watt Tube Amp. Amazing equipment there…

  3. David Rysdam says:

    This is a clip from the amazing Mechanical Universe series that changed my life as a kid. A few years ago, I emailed the host/creator David Goodstein to thank him for it and he graciously replied. You could probably ask him what that equipment is yourself.

  4. John B. Egan says:

    You just need a tone generator (Think synthesizer) and an amplifier. Most home recording studios have that. Also hear it works best on real crystal…Not cheap formed wine glasses. There are several effective vocal ‘glass breaks” on Youtube : http://www.youtube.com/watch?v=amuPoPkAlx8&feature=fvwrel

  5. jammit says:

    I apologize in advance for being “Captain Obvious”.
    The Mythbusters did an episode about breaking a wineglass with just a human voice. It might make for a good reference.

    1. goobering says:

      +1 for the Mythbusters episode. Couple of useful hints from http://www.youtube.com/watch?v=WFbUpUE9KiU&feature=related . Tap the glass and use the frequency it produces as a starting point for your signal generator sweeping. Looks like my original guesstimate of 7-8kHz was waaaaay off. More likely to be in the range of 500-700 Hz. A straw placed in the glass will start bouncing around when you’re in the vicinity of the resonant frequency and give you a nice visual cue.

      1. redfive1976 says:

        Two important things to note on the Mythbusters ep:
        1. When they did the amplified tests, they used a slab of plywood with a 2-inch hole in the middle as their waveguide; pretty effective
        2. When Jamie the singer did it unamplified, his lips were pursed into a similar waveguide-type shape; also pretty effective
        So, focusing the audio waves is pretty important.

  6. goobering says:

    The setup I’d recommend for doing this would be:
    A signal generator as your audio source (PC would be useful!)
    An amplifier for your audio source
    A reasonably loud speaker capable of producing frequencies up to about 15kHz
    Something with a fairly narrow opening for audio to travel through (AKA an acoustic waveguide). You could use an acrylic sheet with a hole cut in it, or something more like the metal waveguide shown in the video.
    A wine glass
    A cardioid pickup pattern dynamic microphone (Red 5 RVD30, Shure SM57), or possibly even an el cheapo electret type mic from Argos.
    A microphone preamp or small mixing desk (dependent on the sensitivity of your oscilloscope)
    An oscilloscope

    If you use an el cheapo electret microphone then your connection’s a doddle. I’d run it into the line of a PC and use a software oscilloscope. Electret mics are powered from the PC so there’s no worries about amplification. If, on the other hand, you use a dynamic mic (which is unpowered and has *very* low signal output) then you’ll need to run an XLR cable from mic to mic preamp/desk and then figure out how to get the output from this into your oscilloscope/PC. This *shouldn’t* be too complicated but without knowing the hardware details it’s a little sticky to give a guide.

    Connect the signal generator to the amplifier.
    Connect the amplifier to the speaker.
    Place your waveguide in front of the speaker. This should help to direct sound waves at a loosely focused area on the glass. Without a waveguide the sound waves will travel here, there and everywhere, hit the glass at different spots and times and inhibit your lovely resonance from building up.
    Put your wine glass in front of the ‘out’ hole on the waveguide.
    Put the mic as close to the glass as you can without touching it.
    Connect the mic to the mic preamp.
    Connect the preamp to the ‘scope.

    Going from the above video, start your signal generator up to produce a sine wave at something like 7 – 8 kHz.
    Get some audio running through your speaker. Probably best if it’s not tremendously loud at this point.
    Monitor the resonance of the glass on your oscilloscope screen.
    With the speaker operating at a reasonable, non-ear-bleedy level, sweep the frequency v…e…r…y slowly upwards until you get a nice clear even sine wave pattern on the ‘scope.
    At this point your glass should be resonating. If you look closely at the top rim of the glass (for the love of god wear goggles) it should look a little fuzzy from the vibrations.
    Fun bit. Gradually increase the audio level produced by the speaker. Keep your fingers crossed. Wear goggles. Stand far enough away to not get glass shrapnel in any of your softer anatomy. The glass should break.

  7. jammit says:

    Now I intend to actually contribute useful information instead of pointing to Google.
    1) The microphone is a standard dynamic 600 ohm microphone. It’s a moving coil type.
    2) The speaker is a standard horn speaker element. The horn part has been removed and replaced with a copper pipe. The pipe focuses the sound better than a horn. A horn tries to spread the sound out.
    (p.s. I finally figured out how to set up Gravitar correctly)

  8. dude says:

    The bronze tube is a sleeved adjustable length tube that can have it’s fundamental frequency adjusted to that of the “wine glass”. It’s basically what I did when I had to help produce the exact same type of physics demo at work.

  9. iyahdub says:

    xAny mic will do ( it is just to see the signal on the oscilloscope, anyway~) . The speaker better be a good one, specially a good studio monitor that has close to a flat frequency eresponse, but i guess commercial hi fi ones will do prob better as they boost most frequencies even more, so goes to show. Then depends just on how powerful the amp you have is !!

    1. Dave Babcock says:

      Speaker doesn’t have to be good at all, just have a good efficiency at the frequency required. You might be able to get an auto horn to work, if you can adjust the frequency. Donno’ if that would entail just some metal bending or a complete re-build…
      Ol’ Bab, who was an engineer.

  10. Roberto says:

    This week a jet plane crashed all the windows of the Supreme Court in Brasilia, the capital of Brazil.
    For a “cool factor” in future demos, use this video.

  11. I just built a glasswrecker for an interactive museum exhibit.

    Learn From My Fails:

    1) You want a horn driver speaker. Paper cone loudspeakers are nothing but heartbreak.

    2) The frequencies are not in the multi-KHz range.

    3) The easiest way to determine what frequency will excite and break the glass is to ping the glass in the presence of a guitar-tuner-type application. ClearTune for iOS is particularly useful in this regard. The frequency must be within a .1 Hz band of the resonance to break at levels around 130dB at the glass surface.

    4) Wineglasses have gotten remarkably strong over the last 40 years. I suggest using used ones with some microscratches because you cannot reliably wreck an average wineglass in the $1-60/stem range fresh out of the box without blowing up the expensive speaker.

    5) Wear ear and eye protection.

    The shattering is awesome when it finally happens. Glass will go everywhere in leetle teeny sharp cutty pieces.

    There is an entire series on making a glasswrecker using a frequency generator and bog-standard amp at http://digital-diy.com/forum/chit-chat/breaking-a-wine-glasses-acoustically-t2198.html

    Have fun, don’t expect early success, budget for a lot of busted equipment if you assume an experimental rather than analysis-driven posture and know that audio companies tend to engage in specsmanship on their data sheets. We made the smoke come out with levels well under the calculated maxima on at least six ocassions at $80ish each.

  12. jammit says:

    It’s a really bad idea to spam a website dedicated to hacking.

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