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The air horn is a simple device, essentially some canned-air with
a plastic horn on top. When pressed, the air rushes out through
an orifice of a size tuned to make a loud noise. The noise an air
horn makes isn't a specific note, rather just something right in the
middle of the human hearing
range where our ears are most
sensitive. This doesn't have to be the case.
It's perfectly feasible to make a tone outside the normal human
hearing range. You could go low, to make an infra sound, deeper
than a fog horn, but this would require a LOT of air and a massive
horn. This isn't practical. Making a high frequency is much easier,
you need smaller components, and possibly higher pressure which
is fine. So what tones are we aiming for... I suggest two separate
air horns with different tones.
The first is at around 18kHz. This is above the hearing range of
normal adult humans, but, crucially, within the hearing range of
teenagers and younger children. It is, essentially a cheap,
disposable use-anywhere mosquito <link>. This may be used by a
responsible adult in a variety of scenarios where children might
need to be distressed without inconveniencing everyone else.
The second model is even higher pitched. say, 35kHz designed to
scare off the majority of animals, racoon rooting through your
garden... give it a blast of the animal-specific air horn.
[bs0u0155, Feb 15 2021]
Ultrasonic and/or infrasonic animal repellent horn powered by compressed air canister [kdf, Feb 15 2021]
nice neon glow
[bs0u0155, Feb 18 2021]
||So... a dog whistle with an adapter for an air can?
||Well, but quite a lot louder, and potentially mounted on a
drone or other vehicle.
||If you COULD make one with a suitably deep, infra sound,
you would have a rhino horn.
||See linked patent. I was actually looking for just
vaguely similar things and was surprised to find
one so close (identical?) to your concept.
||Even with that patent, I cant find anyone
marketing this. Ive seen lots of ultrasound critter
repellers - from pocket sized up to big outdoor
installations - but they use electric ultrasound
transducers rather than airhorns.
||[kdf] huh. Well, that is very similar. I did a brief search and didn't pull that up. I'm surprised it was granted, it's quite broad. They didn't however, include teenager repellent as a major use case. Teenagers are clearly a larger menace than the combined animal kingdom...
||If you have one at 18kHz, you could make another at 19kHz
or so. Then, if you need an audible noise, you blast them
both at once.
||//if you need an audible noise//
||How unpleasant. How about a nice relaxing neon bulb to
indicate the presence of a teenager repellent din? Or
perhaps a streamer attached to the horn that would flap
around in the expelled gas?
||"How about a nice relaxing neon bulb?"
bs0u0155, Feb 17 2021
||Or a strobe light, as anticipated in that patent from 2009?
||Thatll never put anyone off,, even if it is NIXie.