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Seeking advice on ultrasound transmission rig
Seeking advice on ultrasound transmission rig
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Old 2nd December 2019, 01:49 AM   #1
pii is offline pii
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Default Seeking advice on ultrasound transmission rig

Hello everyone!

I see some stunning homebuilds on these forums.

I wonder if there is anyone out there that can advise me.

I'm trying to make a cost-effective (<$60 if possible) ultrasound transmission beacon: 17.5kHz - 19.5kHz coming from a RaspberryPi.

I need to add an amplifier and a Tweeter.

I found a promising looking tweeter on Amazon here which goes up to 22kHz. Also it only cost $18 for two units.

However I'm not at all sure on the amp.

Can anyone advise?
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Old 3rd December 2019, 05:40 PM   #2
Mark Tillotson is offline Mark Tillotson
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sensitivity 72.5dB? That's definitely not the driver you are looking for!


Cheap piezo tweeters may be a better bet. Until you know the sensitivity of the driver you won't know how much power your amp will need.

Last edited by Mark Tillotson; 3rd December 2019 at 05:47 PM.
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Old 3rd December 2019, 08:56 PM   #3
adason is offline adason  United States
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definitely piezo
they 'work' all the way to 40kHz
well, work, they make some sound
they sound like crap with music,
response is like roller coaster
but as ultrasound generator that's just fine
dogs, mosquitos and bats will love you

GRS PZ1016 2" x 5" Piezo Horn Tweeter Similar to KSN1016A
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Old 4th December 2019, 05:04 PM   #4
pii is offline pii
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Thanks @adason (�� on the Osho Avatar, ❤️Osho).

I'm a little concerned about the frequency response smoothness. We are currently transmitting (17.5–19.5)kHz and we need a reasonably flat response within this range. It can be hard to get spec sheets with frequency response curves for low-cost units -- e.g. I can't find a sheet for this one. Nevertheless, it's cheap enough to be worth trying it out, i.e. skip straight to field test.

How would I go about sourcing a suitable amp for that unit? Do I ONLY need to look at the power-rating (in WATTs)? Or do I need to consider the resistance (Ohms) of the driver?
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Old 4th December 2019, 07:41 PM   #5
Mark Tillotson is offline Mark Tillotson
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You won't get a flat frequency response anyway at those frequencies due to multipath/reflection/standing-wave issues in the environment.


Sound power out = sensitivity x power in. Sensitivity is usually quoted for 1 watt drive at 1m distance from driver. The frequency for that sensitivity is also hopefully quoted!
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Old 4th December 2019, 08:30 PM   #6
adason is offline adason  United States
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pii, do you require flat fr response between 17.5 to 19.5 kHz? how flat? +/- few dB?
piezos will not meet that criteria
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Old 9th December 2019, 07:53 PM   #7
pii is offline pii
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So grateful to find this community.

@adason, how are these graphs being generated?
I would like to say "reasonably flat" frequency response across our carrier-band.
We don't have an exact technical requirement; we are at the mercy of the hardware.
There is going to be a performance/cost curve, and I can't pre-empt exactly where on the curve we want to be.
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