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Comment by dathery | Hacker News Reader

I could see this happening. Zoom for example already uses ultrasonic sound to detect what conference room a laptop is in for one-click screen sharing.

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I wasn't aware audio hardware on laptops can emit ultrasound. Aren't those filtered to be below 22KHz?

Most adults can’t hear > 18kHz.

Related, there are devices you can buy to repel teenagers: https://www.today.com/news/controversial-mosquito-sonic-devi...

I can hear whatever my PC can output, but I can't hear anything in our Zoom meeting rooms. Maybe it's low volume, though.

> I can hear whatever my PC can output

This would require measuring equipment, since you can also only hear what you PC can output that you can hear. ;)

I do use my phone to measure, though the mic might be filtered as well.

To sample a analog signal in digital you always have to filter it. Otherwise you would a lot of aliasing because of the Nyqst thing.

As someone who grew up with iPhones coming out around the time I was in middle school and apps producing noises like this were used as pranks in class I have to ask that people don't do this. The sound is painful.

Yeah I'm pretty sure there are plenty of adults that can hear those frequencies though. It's not like everyone reaches 18 and suddenly loses hearing.

Stupid devices IMO. When they first came out I downloaded a sample audio file from the manufacturers website to see if I could hear it. I couldn't.... because they encoded it as MP3 and it was completely filtered out by the encoding! Literally an empty file.

I used to hear the remote from TVs especially old Philips ones and LG's with the single chip on them. That was until I hit 44... after that is hit or miss or just imagining.

But weren't old remotes all IR?

Some very old remotes used what effectively amounted to high frequency tuning forks. Example: https://www.theverge.com/23810061/zenith-space-command-remot...

No, not all were IR.

But all of them made by "LG" and featuring a single-chip design are either IR or RF.

Those will still have a ceramic resonator in them, as they’re cheaper than a quartz crystal. Hard to imagine them being audible, but not impossible.

In our region, some people have devices to repel moles or marten using "Sounds that are inaudible for humans". I have yet to come near to one of these devices that I can't hear. And it's not only me, my wife can also hear them, as well as my daughter. I also know some people who can't hear anything from these devices, but it feels like the statistics about what people can hear and what not are not that up to date.

Agreed. My mother thinks I'm lying. I will admit I feel a little bit special that I can hear her motion activated cat-poop repeller thing.

I visited her recently and wasn't sure if I had finally aged out of my sensitive ears (34 now) or if her batteries needed to be replaced.

FWIW I wonder if people do not experience physical pain from certain sounds, because people seem to be totally fine with sirens but it feels like I'm having a spike pushed into the side of my head.

When I was a teenager, the applause from the end of year school talent show caused me physical pain — enough that the teachers noticed and got me out of the hall.

This no longer seems to be the case, as I'm living right by a major junction and get random full volume sirens at least six times in the average day. I hate them, but they don't hurt.

Personally I can't hear much above 15.5 kHz and I can hear these devices, so they're not even particularly high-pitched.

These are everywhere in Japan as anti loitering devices

Courtesy of anti social boomers. If I ever meet the person who approved the installation of this kind of system I swear I'll punch them in the face.

i wonder if that is what those super irritating high-pitched screeching noises near some buildings in shibuya...

it seems to occur only late at night but could be wrong... i had assumed they were for driving rodents away but i guess not?

Chromecasts do it too, for pairing purposes. I’m sure other devices use it for clever purposes as well.

Teams does it too, I've had meetings where I've been able to audibly hear it coming from devices

Not great if you have dogs in the office unfortunately.

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