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Detecting sound
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Detecting sound

by chassmith on Fri Mar 13, 2009 9:41 pm

I would like to detect sound in the 17-19 kHz range for a project idea that I had. Does anyone have any suggestions for a sensor to choose?

Thanks,
Chas
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Re: Detecting sound

by zener on Sat Mar 14, 2009 3:19 pm

You might get better answers if you give some idea what you are doing. Anyway, that is basically ultrasonic so you can search for ultrasonic receivers/transducers. Digikey has some. There are also modules made for various ultrasonic functions. It just depends what you are trying to do.

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Re: Detecting sound

by chassmith on Sun Mar 15, 2009 3:15 am

My hearing doesn't go that high. My student's hearing does. I'm looking to be able to detect when one of them uses a mosquito ringtone.
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Re: Detecting sound

by phil.drummond on Sun Mar 15, 2009 6:13 am

You could try spoofing the room and watching for the student who goes for their cell phone.
Set a "mosquito" ring tone on your own phone and trigger it while their heads are down on an assignment. :)
If you get a "hit" on your spoof, tell the room what you did and point-out the student who let the cat out of the bag. Peer pressure will get them hammered and they will know you are wise to the method. They will have to try another way of getting past you.
I know when I was in school, the teachers who were smart were the ones I just avoided messing with. :)
They didn't have cell phones back then, but we tried all sorts of other ways to contact each other when we were not allowed.

As for detecting the sound, research "Bat Detectors". These simple devices frequency-shift the high frequencies above our hearing, those which the bats use for echo-location, down into the range we hear. You put one in your pocket, and an earphone in your ear and you hear all the sounds in the room, including the mosquito ring tones. Still, without observing the students, you will have trouble telling direction to the phone.

Good luck!

Phil
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Re: Detecting sound

by zener on Sun Mar 15, 2009 3:23 pm

Bat detector!! Cool! I will check that out.

Here is an idea: Make a device that when it detects the mosquito tone it plays Barry Manilow (Mandy). The problem should then solve itself.

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Re: Detecting sound

by gamerfreak on Sun Mar 15, 2009 5:05 pm

Chaney Electronics has a Ultrasonic Sniffer Kit, which does exactly what you want. They also have a Bat Detector Kit. I'm fairly sure the only place to order those is Goldmine-Elec.
Its not as cool as engineering something yourself, but it gets the job done :wink: .
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Re: Detecting sound

by chassmith on Tue Mar 17, 2009 6:09 pm

Thanks everyone. I'll look into those.
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