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Author Topic: ultrasound (12-30kHz) generator and microphones  (Read 2893 times)
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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
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I don't think you connected the grounds, Dave.
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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.
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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
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That is an interesting problem.
I wonder what bat detectors use?
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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 -
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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

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tests on tinnitus.
Can you say more, I have tinnitus so I have a strong intrest in this.
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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.
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Yes well mine was too much loud rock music in a middl age crisis that lasted too long.  smiley
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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 smiley
Massimo
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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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