Detect Sound of Breaking Glass

[Anonymous]

Hello. I'm an undergraduate working on a project to build a home
security system using DSP and NI's Speedy-33 board. My question is :
1) how can I detect breaking glass sound
using LabView?
2) how to connect external hardware(e.g
siren, lights) to the Speedy-33 board
that will be activated if breaking
glass is detected.

Thank you.

[Kjell-E]

For detecting the sound of breaking glass, I believe that it has a very distinct set of harmonic frequencies.

Try recording the sound of breaking glass at the best (mono) quality possible. You can use a sound recording program to do this. You should try to record a few different samples of glass to check for commonalities.

Also record other random noises that could occour in the environment.

Next, write a VI that reads the files and play around with FFT analyzis of the sound files. Use different window sizes and types (hamming, flat..)

If I am not mistaken, you should be able to find/realize that "breaking glass sound" has a very distinct FFT profile. This profile, or possibly set of profile, could then be generalized and saved, and used to compare with the FFT of incomming sound generated by your speedy board.

As for interfacing stuff, without having seen or read about the speedy kit at all, if you have any form of digital output capability from the board, and I am pretty sure you do, you can either buy a solid state relay (sort of expensive) which basically allows you to controll a big current just by using your digital output.

You can however, sort of build your own custom SSR by wireing the digital output to a small and simple transistor circuit which in turn powers a standard relay.

Given that this is an undergraduate project, I think the information I have given should be enough in terms of hints to get you started.

If you have specific questions/problems for your vi's, then of course post those too!

[Jarrod_S.]

One question: are the police going to be called when someone drops a wine glass? (I couldn't resist... 🙂 )

[AnalogKid2DigitalMan]

You may want to investigate detection of ultrasonic frequncies >20KHz, I believe breaking glass contains a lot of energy in this part of the spectra.

[unclebump]

Look at an acoustic emission (AE) sensor from Kistler. I would think frequency could be different if someone breaks it with a piece of metal, or a hand wrapped in a towel.

[Kjell-E]

ok, this is just speculations on my part, but I think what you normally look at to detect the sound of breaking glass, is the sound of the glass interacting with itself. I'm sure the sound at impact will be different under different scenarios, but I speculate if not the time after impact is the most interesting. E.g. when the pieces break away from the glass window and when they bounce around on the floor??

I'm curious as to what they find out, so I hope the original poster will report back to us at some point to let us know how it went.. 🙂

[Rashid]

And what about cutting glass sound? I mean when a man uses suction cup with diamond cutter, and after that silently removes a part of the glass. (Remember "Hudson Hawk" with Bruce Willis?)

Best wishes, 😉

Rashid.

[tst]

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@Rashid wrote:

Remember "Hudson Hawk"?

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Certainly. "What's Nintendo?".

Or, to be more safe, "Would you like to swing on a star? Carry moon beams home in a jar...".

[Henrik_Volkers]

What type of detector do you want to use?

One test you should do: Just snap a coin with your fingers on the window. We used to do that in the past to fire the alarm without breaking anything. (Hoping that my childs will not read this)

[RaymondCampbell]

HS Senior who's got the same project..

BUMP! :manmad: