I live in Japan, Tokyo, and sometimes I come across these annoying/distracting high-pitched noises even in residential areas. They are a nuisance for bypassers too, if you've got ears young enough. But the residential areas don't have any problem with loitering youngsters, so I keep wondering if the noise is targeted against pests or wild animals. This article made me think if I should seriously start measuring the volumes and frequencies objectively. What kind of equipment would you need to get some data to get started with?
I've encountered this a few times in Tokyo myself; from memory at the very least outside of a mall in Shinjuku and outside of a building a block or two away from the Shibuya Scramble crossing. My traveling companion never noticed them until I pointed the sound out, so for those who find themselves in Japan pay attention if you notice a pressure in your ears and a high-frequency sound that seems to get more/less intense as you walk. If you follow the sound to its source you'll probably find that it seems to be coming from a metal trapezoidal horn, usually mounted from ceilings in places outside buildings from standard electrical junction box with exposed conduit. The sound itself is a constant, high frequency (18-20khz?) ring, and can get pretty intense as you approach the device.
I believe they're anti-loitering devices targeted at young people, who can hear a higher range of frequencies than older people. I've encountered them all over the US (if you're in the Bay, there's one mounted outside the Twin Peaks Tavern in Castro), though usually they pulse rather than emit a constant buzz. They're sporadic but common in Tokyo for sure, I encountered at least a dozen in the combined week or so I spent in various regions there. It was always creepy to me whenever I'd discover one, the sound was slightly nauseating if I ever got too close and left a strong negative impression, as though they were some sort of threat.
If anyone knows more specifics about these things btw, happy to have details. I spent a period of time trying to find the exact device but never could find any pictures of them, and unfortunately neglected to when I was actually in Japan.
Normal computer recording only goes up to 48kHz (24kHz Nyquist rate, with analog filters lower than that to prevent aliasing) but high-quality equipment might support 96kHz or even 192kHz.
even a headphone plugged in wrong is a good enough sensor to start.
when it gets bad you start looking at designing your own ribbon elements and considering active pickups. when it gets worse you may find yourself deeply concerned about ADC and clock skew.
And many modern sound card IC sample at an effective rate of 192kHz and use internal DSP to downsample that to the requested sample rate.
Much easier to design a good low pass filter on the cheap when your Nyquist frequency is on 96kHz instead of 22kHz.
So the frontend of the sound card might actually be remarkably wide.
I assumed that most of the normal consumer-level stuff is (perhaps very deliberately) insensitive to sounds that human ears are insensitive to? The common codecs, for sure, tend to have rather harsh cutoffs around 20kHz (the common sampling rates being 44 or 48kHz, and the Nyquist frequency half of that, 22-24kHz, so you have to start filtering well before?)
Plus, I'd rather not walk around with a laptop. But perhaps smartphone apps are capable of consuming the mic input unfiltered? (Never tried recording APIs for that purpose)
Studio Six Digital makes the very useful app AudioTools. They test all iOS devices to create generic profiles for the built in mics. They’ve found them to be very consistent which is kind of remarkable for a consumer cell phone device.
I came across some of these in Tokyo recently as well. Super annoying, and I'm 40. I thought I'd be immune by now. I assumed they were intended to drive away cats or rats or mosquitos.
Can't speak for Tokyo, but there are streets in my American suburban neighborhood I avoid because of (presumably) animal-deterrent noises. I'm also 40, and surprisingly can still hear them - and an audiologist had my ears tested last month, and said my hearing is excellent for my age.
Which is a bummer when I have to cycle around several blocks to avoid hearing the squeaks that are physically painful to my ears.
In my experience those regulations are only ever used to shut down parties with loud music. If it's any sort of industrial or non-obvious noise, good luck getting people to care about it. I have bad memories of complaining in an online community about the extremely loud safety beeps from construction vehicles operating next to my home and being told I was a monster because I must want children/workers to die - and that was a sound whose mere existence didn't need to be explained.
Yeah, maybe. But the hassle of trying to convince the town this house is in - which isn't my town - to do something about it is significantly more difficult than just riding my bike around the place.
I've always wondered about that. I'm also bothered when walking around Tokyo (it's very prevalent in Ginza for some reason). I've also seen it in other cities in Japan but I've never had that issue in other cities in Asia (Hong Kong, Shanghai, Bangkok, etc..)
I'm 40 too but as a kid, I was very bothered by the high pitch wine of the tv turning on, so I'm guessing I've always been rather sensitive.
There are lots of "rat deterrant" devices which emit varying tones 15-20 kHz. they often emit chirps or frequency sweeps. Sometimes always-on, sometimes with an IR sensor (in battery powered versions).
