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Topic: ultrasound (12-30kHz) generator and microphones (Read 3305 times) previous topic - next topic

mcamarda

Hello everyone,
my girlfriend is a doctor in Audiology and she asked me if I could help her on building an ultrasonic generator (in the range 12-30kHz) for tests on tinnitus.
I was hoping to use a signal generator and an oscilloscope that I already have along with two transducers, but I think it is more complicated than that ....
We found small piezo speaker but we are having many difficulties with the microphone, I found peizo transducers (sensors for parking, working at around 30kHz), but does not seams to work at the frequencies I am interested on. nfortunately, if I can not control the generated sound it does not make sense to experiments with the speakers.

Can you give me some advice on how to make this I/O system?
thanks
Massimo

AWOL

The ultrasonic transducers used in rangefinding apps tend to resonate very strongly at their designed frequency, and not respond very well at all at other frequencies (except maybe harmonics).
Maybe some high-quality tweeters would be a better bet.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

mcamarda

Yes, that was also my idea.
I both, just for an initial try, a cheap tweeter that should go, in principle, from 1.8kHz to 30kHz.
My main problem is with the imput, that is with the microphone, I don't know what to use.
Massimo

AWOL

That is an interesting problem.
I wonder what bat detectors use?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

robtillaart

Quote
I wonder what bat detectors use?

saw this a few months back - http://www.elektor.com/magazines/2011/november/simple-bat-detector.1971945.lynkx -

no idea about the quality ...

from the link above a 40Khz sensor - http://nl.farnell.com/prowave/400sr16p/receiver-ultrasonic-40khz-16mm/dp/1007338 -
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

mcamarda

I have red about bat detectors. 
I found a very nice thesis:   http://web.wm.edu/physics/Senior%20Theses%202004/Loncich-Kristen.pdf. 
The problem is that these detectors work only close to the 40kHz frequency (from datasheet).
so I don't think I can use them.
The "Knowles Acoustics FG-3329" seams interesting, I am looking for it, my fear is the solding and the amplification, I am not very good on that...
Massimo


Grumpy_Mike

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tests on tinnitus.

Can you say more, I have tinnitus so I have a strong intrest in this.

dxw00d

Me too.

There was a study done quite recently on tinnitus. I caught a bit about it on Radio 4. Apparently they still have no concrete idea what causes it. Apparently there is a huge variety of triggers, ranging from the obvious prolonged exposure to loud noise, to less obvious causes like a bereavement.

Grumpy_Mike

Yes well mine was too much loud rock music in a middl age crisis that lasted too long.  :)

mcamarda

I have tinnitus too.  The idea of my girlfriend is that there might be different "kind" of tinnitus.  Indeed some people (like me) are not bothered from it, other go almost crazy.  So, she would like to explore the range of frequencies above the human level (above 18kHz) to understand if this region is impacting the patients.
I am tring to build a I/O sound system on these frequencies, but I am a Physicis not an Engineer, so that I am looking for a help :)
Massimo

Grumpy_Mike

Thanks for the explination.
My son by the way could hear up to 24KHz.

I would just use a normal microphone and speaker but calibrate them to compensate for the drop off in sensitivity at these higher frequencies. If you can plot the curve then you could match that to the opposite function with an active filter, and produce a flat response.

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