Seeking advice on ultrasound transmission rig

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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?
Thanks @adason (&#55357;&#56397; 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?
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!
music soothes the savage beast
Joined 2004
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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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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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