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Detecting Ultrasound

If you want to compress the range of 0-30 kHz to something like 0-12 kHz you can do that with a switched capacitor delay chip like the Panasonic MN3007.

It will work like the bat detector, except it won't need to clip and threshold the audio. You will need to use a slow ramped VCO (continually ramping the sampling frequency down) in order to do this. There are some projects at:

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You may be able to adapt a flanger, for instance, to suit your purpose.

The control voltage to the sampling VCO will be a sawtooth wave. Unfortunately, you will hear the sawtooth period as an artifact in the output. Maybe you can filter it out.

I guess an all-digital solution is better ;-)

Frank Raffaeli

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Frank Raffaeli
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Hmm. i was going to say, if it worked, it would be cutting edge technology! :)

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Jamie

A sharp observation indeed.

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clifto

On a sunny day (Tue, 13 Mar 2007 22:42:58 GMT) it happened Rich Grise wrote in :

Mirror, webcam, helper,

Reply to
Jan Panteltje

Agree. Even a bog standard electret for $1 will do it - probably wouldn't even need an amplifier......if you want to get sophisticated, put it in the end of a piece of 30mm plastic pipe - voila, directional microphone....

The alternative is you are just being paranoid......but I know you know that anyway...

Andrew VK3BFA.

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Andrew VK3BFA

It was, a millennium ago.

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Michael A. Terrell

==================== I found an Archer packaged (for Tandy) cat no 270-092B Electret Condenser Mike Element in its original Package, complete with response curve. From 30 - 3000 Hz the response is flat. From 3000 Hz to 5000 Hz the response increases by approx 10 dB. From 5000 - 9000 Hz the response drops such that it is back to its original level at 9000 Hz .Above that freq the response drops. Response curve is not extended beyond 12000 Hz

Frank GM0CSZ / KN6WH

Reply to
Highland Ham

Hello Andrew,

Do you know of any freq response curves on the web for the garden variety electrets? I've looked and haven't found any.

Thanks,

Chuck NT3G

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Reply to
chuck

Google for 'bat detector'.

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Nico Coesel

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PeterD 

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