8 ms·

Ultrasonic investigations in shopping centres

351 points by GolDDranks 2y ago

GolDDranks 2y ago
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?
- h2odragon 2y ago
  > what kind of equipment Any microphone hooked up to a laptop with a microphone input. Or a phone running some audio spectrogram app. Getting started is very easy, but then you'll be constantly tempted by better sensors, more sensors, more channels, more analysis...
  - datameta 2y ago
    And you might accidentally get into field recording and manipulating sound with a portable modular synth... Oops
  - immibis 2y ago
    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.
    - h2odragon 2y ago
      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.
      - immibis 2y ago
        It doesn't matter what your microphone can do, because your sound card does the filtering and digitization.
        h2odragon 2y ago
        it might; depending on your goals: microphones color the sound and their limits can be as valuable as their capabilities, in the right context. see the mics that harmonica players lust after. "You traded the Cadillac for a microphone? ... I can see that." I believe many sound chips still have ways around any pee-processing they may apply, might check the folks using them for low rate oscilloscope inputs
        RF_Savage 2y ago
        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.
  - dylan604 2y ago
    > but then you'll be constantly tempted by better... this is a likely outcome for any new hobby
  - GolDDranks 2y ago
    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)
    - lanthade 2y ago
      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. More info here: https://studiosixdigital.com/audio-hardware/generic-audio-hardware/iphone_3gs_microphone/ https://studiosixdigital.com/audio-hardware/generic-audio-ha...
      - EricE 2y ago
        Studio Six tools are the cheapest and easiest way to dip your toes into SMAART - which if you are into audio can be one heck of a rabbit hole :)
- modeless 2y ago
  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.
  - pavel_lishin 2y ago
    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.
    - B1FF_PSUVM 2y ago
      > squeaks that are physically painful Those may be covered under loud noise regulations, if the official measuring machinery has the cutoff frequency set high enough (no reason why not).
      - pavel_lishin 2y ago
        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.
      - anigbrowl 2y ago
        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.
      - deleted 2y ago
        [deleted]
- mholt 2y ago
  Those are probably vole deterrents.
- louthy 2y ago
  Omnidirectional reference microphone would do the job.
- deleted 2y ago
  [deleted]
- londons_explore 2y ago
  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).
- pants2 2y ago
  You almost certainly want some sort of Audiomoth. They record at up to 380kHz and have all sorts of useful tooling.
- malwrar 2y ago
  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.
spondylosaurus 2y ago
Have you ever listened to a badly mixed song with a persistent high-pitched whine undercutting part (or all) of it? Certainly that's not on purpose either, but I doubt anystudio equipment is giving off an intentional "test" whine either, so I've always wondered how that ends up happening.
- liminalsunset 2y ago
  I've got an example of this: Some Blackpink songs (cannot remember which ones, possibly Playing With Fire or DDU-DDU-DDU) were mastered and released on Spotify/iTunes [unsure if has been removed now] with a 18-19kHz carrier tone (iirc it was actually a number of tones) modulated. The signal was very loud. I first noticed this in a friend's car and assumed it was because the song was ripped from YouTube, but later realized that all of the versions have this. The reason for this is because at concerts, you can buy a piece of merch called a lightstick. Essentially, it is a STM32 and a mems microphone that is demodulating the carrier signal, so it can flash in time with the music. The tone has to be <ultrasonic because it has to work with consumer speakers and the mic in the device. I assume the theory goes that anyone who has been to enough concerts to have a lightstick is no longer capable of hearing the noise.
  - kmeisthax 2y ago
    Alternatively the sound is in there deliberately so that if you have a lightstick it'll start playing in time with the music.
  - gravescale 2y ago
    Relatedly the wristbands used at for example, Taylor Swift concerts use 38kHz IR floodlighting for the control signal. Recently HN'd: https://news.ycombinator.com/item?id=40492515 https://news.ycombinator.com/item?id=40492515
- matteason 2y ago
  This happened recently on Taylor Swift's rerecording of 1989 - a persistent tone at 15KHz on multiple tracks [0]. The Taylor's Version records have to be some of the most carefully-produced albums around, given that the goal is to accurately reproduce existing recordings, so it's amazing that it made the final release. [0] https://old.reddit.com/r/TaylorSwift/comments/17iv3r2/for_people_who_can_hear_the_buzzingstatic_in_1989/ https://old.reddit.com/r/TaylorSwift/comments/17iv3r2/for_pe...
amelius 2y ago
No mention of how bad this must be for dogs and other animals that can hear better than humans.
- _Microft 2y ago
  I always wondered the same about ultrasonic parking/proximity sensors on cars.
  - HeatrayEnjoyer 2y ago
    What cars produce ultrasound? I thought radar is used.
    - matteason 2y ago
      Wikipedia says both ultrasonic and electromagnetic are used: https://en.wikipedia.org/wiki/Parking_sensor https://en.wikipedia.org/wiki/Parking_sensor One of the references is for a Mercedes system that uses ultrasound
    - buildsjets 2y ago
      Every single car from every manufacturer that has PDC sensors in the bumper, which are typically visible as 4 circular sensors on the surface of the bumper.
    - ptero 2y ago
      Most cars have ultrasonic sensors for parking and radar for longer range detection, such as cruise control.
    - ornornor 2y ago
      I hear some car alarm sensors when passing by, the ones that will trigger when someone is about to park too close and hit the armed car.
  - houseplant 2y ago
    induction stovetops create extremely loud high pitched noises, some get up to 100+ decibels. You can't "hear" it but at higher heat levels you can definitely "feel" it in your ears.
hehdhdjehehegwv 2y ago
It’s been used for ads for years.
- pavel_lishin 2y ago
  How so?
  - paulmd 2y ago
    https://en.wikipedia.org/wiki/Cross-device_tracking#Ultrasonic_tracking_2 https://en.wikipedia.org/wiki/Cross-device_tracking#Ultrason...
  - xphilter 2y ago
    I brought some class actions years ago alleging the unlawful use of this tech for essentially ads purposes: https://topclassactions.com/lawsuit-settlements/lawsuit-news/golden-state-warriors-seek-dismissal-app-spying-class-action-lawsuit/ https://topclassactions.com/lawsuit-settlements/lawsuit-news... and https://www.freeadvice.com/legal/lisnr-responds-to-lawsuit-that-accuses-app-of-eavesdropping-without-consent/ https://www.freeadvice.com/legal/lisnr-responds-to-lawsuit-t...
    - Etherlord87 2y ago
      1st link: claim dismissed. 2nd link doesn't work for me (access denied).
jszymborski 2y ago
Oona's blog posts are consistently bangers; always a treat when she posts a new one.
tlb 2y ago
Has the hypothesis that this is noise from a class-D amplifier (which I assume most commercial speakers use) been eliminated? Those generally switch at MHz frequencies, but have subharmonics all over the place except the ones that have been carefully eliminated by filtering. I wouldn't be too surprised if there was a cheap brand of class-D amplifier that had a 20 kHz tone.
- kurthr 2y ago
  I'd also be suspicious of this. You can also get a lot of beating artifacts from having many amplifiers in close proximity. If the speakers were still larger "mid-range" horns as were seen in decades past, this also might be less of an issue (low efficiency above 10kHz), but for cost/aesthetic reasons the speakers have shrunk quite a bit so they no longer mechanically filter much. If the problem was something everyone could hear it would likely be fixed, but since it's a minority, it's likely to persist. One other possibility for active US is crowd tracking. I've seen solutions that monitor # people and walking speed at doorways using ultrasonics. A lot of "one way" doors also use simple US detectors.
instagib 2y ago
Bistatic 0. one transmitter + two receivers. Very fun topic as I worked on a few and sync them up as the transmitter radar needs to connect to the second receiver radar (usually a full radar for redundancy). Multistatic is fun also as they employ many covert receivers. Had many war game scenario conversations about the setups. Maybe they’re getting a bistatic return with multiple microphones separated in distance enough to be significant. Ultrasonic frequencies generally start at around 20,000 Hz (20 kHz) and can extend up to several gigahertz (GHz). 1 0. https://en.m.wikipedia.org/wiki/Bistatic_radar https://en.m.wikipedia.org/wiki/Bistatic_radar 1. https://www.rfcafe.com/references/general/ultrasonic-spectrum.htm https://www.rfcafe.com/references/general/ultrasonic-spectru...
fullspectrumdev 2y ago
I had almost forgotten about the “Mosquito” devices for deterring youths that became ubiquitous in some areas during the late 2000’s and early 2010’s. They were quite expensive and I know of a few people who got annoyed and specifically vandalised them due to the annoying sound.
- i80and 2y ago
  I'm glad those seem to have mostly faded away? The installation of them especially in spaces open to the general public has always struck me as deeply sick and antisocial
  - fullspectrumdev 2y ago
    There’s still a few around where I live, way less than before though and I think it’s old installations that somehow still function instead of “net new”. What’s awfully irritating is that I can still hear them. I’m in my 30’s with pretty gnarly hearing damage, and can still hear that frequency range.
  - houseplant 2y ago
    I believe they were harming birds and insects, but I don't think someone using a mosquito tone to deter human beings cares much for wildlife health
- michaelcampbell 2y ago
  People they were designed to keep from "hanging out" no longer "hang out" outside any more anyway.
mannyv 2y ago
Cruise ships do this. It drove my kids crazy.
doughecka 2y ago
I work for a manufacturer of PA systems, our amplifiers only do a periodic test every few minutes, one channel at a time. We measure the current the speaker circuit draws, and if that changes drastically we know something is wrong.
transpute 2y ago
> .. there's a clear Doppler shift in the reverb. The frequency shift goes from positive to negative at the same moment that the scooter passes us, seen as the wideband wheel noise changing color.. The speed of sound at 15 °C is 340 m/s. The maximum Doppler shift here seems to be 350 Hz. Plugging all these into the equation we get 11 km/h, which sounds like a realistic speed for a scooter.. Automated speed trap in the car park.. Doppler radar, https://en.wikipedia.org/wiki/Doppler_radar https://en.wikipedia.org/wiki/Doppler_radar, also applies to WiFi reflections, which can be visualized, https://www.youtube.com/watch?v=g3LT_b6K0Mc https://www.youtube.com/watch?v=g3LT_b6K0Mc. Upcoming 2024 "AI" PCs, tablets and phones with NPUs and WiFi 7 can use machine learning and doppler reflections to infer human activity in 3-D space (proximity, movement, heart rate, gestures), via IEEE 802.11bf WiFi Sensing, https://www.technologyreview.com/2024/02/27/1088154/wifi-sensing-tracking-movements/ https://www.technologyreview.com/2024/02/27/1088154/wifi-sen... > Soon, thanks to better algorithms and more standardized chip designs, [WiFi] could be invisibly monitoring our day-to-day movements for all sorts of surprising—and sometimes alarming—purposes. Yes, it could track your breathing. It could monitor for falls. It may make buildings smarter, and increase energy efficiency by tracking where people are. The flip side of this, however, is that it could also be used for any number of more nefarious purposes. Someone outside your home could potentially tell when it’s vacant, or see what you are doing inside.
skmurphy 2y ago
Very interesting. I can remember being able to hear a high pitched tone when I was 4-6 shopping with my mother in department stores that seemed to get louder when we approached flush mounted speakers in the ceiling. This article measures the frequencies and explains it's a normally operating feature of the systems.
- raverbashing 2y ago
  I'm not sure I ever managed to hear a 19kHz tone, but I'd say it might have been possible (or the tone was a lower frequency one). But yes the old CRT whine I could definitely hear
  - skmurphy 2y ago
    I was young. My mother could not hear it and thought I was just being annoying. This is several decades ago, now I can barely hear my turn signal blinker and am preparing to emulate my father's practice of driving a few miles with his blinker on after signalling a lane change.
    - metabagel 2y ago
      One thing that can help is pressing the turn signal lever with less force than is needed to latch it. This should cause the indicator to flash three times and then stop. It’s an operating mode I wasn’t aware of for decades.
      - joecool1029 2y ago
        Not all cars do this, german car feature? (only VW's I've driven from 2000's onward seemed to have)
        lsaferite 2y ago
        My Kia has it as well.
yard2010 2y ago
> Use it to deliver ads somehow Please don't write such things on the internet
- MichaelMug 2y ago
  It’s clearly written it’s an idea. I don’t know what you’re implying here.
  - jfengel 2y ago
    He's saying not to give them any ideas.
- ale42 2y ago
  Having read this blog in the past, I imagine the author was sarcastic on this one.
ricardobeat 2y ago
Totally speculative territory, but I’ve had headaches when going to a shopping center since I was a kid. It’s infallible, one to two hours and my head is exploding. I’ve always attributed it to the noise, crowds and sensory overload but it never happens elsewhere. Could it be?
- LorenPechtel 2y ago
  Perfume, perhaps? There are things I'm sensitive to even though I can't actually smell them.
- e40 2y ago
  Smell, too. Clothes stores always smelled horrible to me and almost always gave me a headache.
- Ylpertnodi 2y ago
  Thanks. I thought it was just me, and circumst
cesaref 2y ago
From the description of the product, I think the intention is that the tone is received electrically at the end of a cable run, so receipt of the tone indicates continuity of the speaker cabling. This high frequency has been chosen to ensure that it is low enough to be amplified and transmitted along with the audio content, and is high enough to be attenuated by the tweeters (so little energy is transmitted), and high enough in frequency so that whatever is emitted by the tweeters will be inaudible. If this is the case, it would sound like there is no need to encode any information on the signal, just it's presence is enough to test the wiring is intact. I'm assuming this is so that if the PA is required for, say, an emergency broadcast, it is fit for purpose. The presence of a <20Khz signal would imply that it was found that in whatever installation was being used that the bandwidth of the amplifiers or some other filter was attenuating the test tone too much to be received properly, so this bodge was put in place.
deleted 2y ago
[deleted]
s1mon 2y ago
I searched the article for "occupancy" and nothing. These ultrasonic tones are most likely ultrasonic occupancy sensors used for lighting and/or security. Typically they're 25kHz or 40 kHz (i.e. out of normal human hearing range), but it's possible that they are measuring some subharmonics of the sensors. I've certainly encountered ones that have mechanical issues and will spit out frequencies that I can hear too well.
Waterluvian 2y ago
I wonder how much spectrum screaming we’re doing from the perspective of other species’ sight and sound.
Havoc 2y ago
> I might have been scrolling through the audio spectrum while waiting for the underground train; What gadget is this person using for this? And audio-y flipper one of sorts?
Marciakhan 2y ago
[dead]
incognito124 2y ago
Her blogs are always a joy to read
CliffStoll 2y ago
FM Radio transmitters broadcast a continuous 19 KHz pilot tone to indicate that it's a stereo broadcast. If it's present, then there's also a 38 KHz AM modulated carrier, which has the stereo information. The main FM modulation is (Left + Right) audio channels - the baseband. The 38 KHz subcarrier is (Left - Right). Notice that the stereo information is likely to be higher noise, being AM and without a lot of power. So on weak FM broadcast signals, you're often better off setting your tuner to mono. Some cruddy FM tuners don't properly filter out the 19Khz pilot tone, resulting in ear-ringing in the listener.
- LeoPanthera 2y ago
  The unfiltered pilot tone was a problem when recording FM radio onto tape, beating against the bias tone and confusing Dolby NR into thinking there was constant sound. High-end cassette decks had an "MPX Filter" which was a sharp 19kHz filter before the recording system.
  - CliffStoll 2y ago
    You betcha! And FM broadcasts have a high-frequency pre-emphasis, which adds something like 10dB of boost to audio high frequencies. This is to reduce high frequency noise that occurs in analog FM systems. Radio receivers have a matching de-emphasis high-frequency cut. Indeed, both vinyl phonographs and audio tape systems employ similar pre-emphasis and de-emphasis. It's the RIAA curve for phonographs. Not sure what the standard is for mag tape.
    - bux93 2y ago
      For mag tape, it's different Dolby NR schemes.
  - egorfine 2y ago
    > confusing Dolby NR Accidental DRM even before the "D" came to be.
_spduchamp 2y ago
I'd like a way to use an array of mics and do some sort of visualization and video overlay to try to see and locate the sources of these kinds of high pitch sounds.
fredthedeadhead 2y ago
What does the author use to measure sound and create those graphs? I'm interested in automatically monitoring an annoying noise that's coming from a neighbour.
- EricE 2y ago
  As others in the comments have already mentioned, Studio Six makes very nice Audio Tools (at least on iOS/Mac, not sure if they are also on Android). Their SMAART module is the cheapest way to get access to SMAART tools - which can be a thing in and of themselves. I use them to asses what's going on with live sound I occasionally mix. What's really nice is they calibrate fairly accurately to Apple hardware out of the box. More than accurate enough for my purposes.
lomase 2y ago
When I used to work with PA systems we had this really cool old-school looking impedance meter. We used to check the continuity of the PA like you do with a resistance meter in an electrical circuit. I dont know much about analog audio but if I am remembering correctly, the device could inject a 1Khz tone that was only heard on speakers with impedance problems. https://toa.co.id/product/zm-104a-impedance-meter https://toa.co.id/product/zm-104a-impedance-meter

351 points by GolDDranks 2y ago

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?

h2odragon 2y ago
> what kind of equipment Any microphone hooked up to a laptop with a microphone input. Or a phone running some audio spectrogram app. Getting started is very easy, but then you'll be constantly tempted by better sensors, more sensors, more channels, more analysis...
- datameta 2y ago
  And you might accidentally get into field recording and manipulating sound with a portable modular synth... Oops
- immibis 2y ago
  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.
  - h2odragon 2y ago
    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.
    - immibis 2y ago
      It doesn't matter what your microphone can do, because your sound card does the filtering and digitization.
      - h2odragon 2y ago
        it might; depending on your goals: microphones color the sound and their limits can be as valuable as their capabilities, in the right context. see the mics that harmonica players lust after. "You traded the Cadillac for a microphone? ... I can see that." I believe many sound chips still have ways around any pee-processing they may apply, might check the folks using them for low rate oscilloscope inputs
      - RF_Savage 2y ago
        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.
- dylan604 2y ago
  > but then you'll be constantly tempted by better... this is a likely outcome for any new hobby
- GolDDranks 2y ago
  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)
  - lanthade 2y ago
    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. More info here: https://studiosixdigital.com/audio-hardware/generic-audio-hardware/iphone_3gs_microphone/ https://studiosixdigital.com/audio-hardware/generic-audio-ha...
    - EricE 2y ago
      Studio Six tools are the cheapest and easiest way to dip your toes into SMAART - which if you are into audio can be one heck of a rabbit hole :)
modeless 2y ago
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.
- pavel_lishin 2y ago
  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.
  - B1FF_PSUVM 2y ago
    > squeaks that are physically painful Those may be covered under loud noise regulations, if the official measuring machinery has the cutoff frequency set high enough (no reason why not).
    - pavel_lishin 2y ago
      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.
    - anigbrowl 2y ago
      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.
    - deleted 2y ago
      [deleted]
mholt 2y ago
Those are probably vole deterrents.
louthy 2y ago
Omnidirectional reference microphone would do the job.
deleted 2y ago
[deleted]
londons_explore 2y ago
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).
pants2 2y ago
You almost certainly want some sort of Audiomoth. They record at up to 380kHz and have all sorts of useful tooling.
malwrar 2y ago
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.

spondylosaurus 2y ago

Have you ever listened to a badly mixed song with a persistent high-pitched whine undercutting part (or all) of it? Certainly that's not on purpose either, but I doubt anystudio equipment is giving off an intentional "test" whine either, so I've always wondered how that ends up happening.

liminalsunset 2y ago
I've got an example of this: Some Blackpink songs (cannot remember which ones, possibly Playing With Fire or DDU-DDU-DDU) were mastered and released on Spotify/iTunes [unsure if has been removed now] with a 18-19kHz carrier tone (iirc it was actually a number of tones) modulated. The signal was very loud. I first noticed this in a friend's car and assumed it was because the song was ripped from YouTube, but later realized that all of the versions have this. The reason for this is because at concerts, you can buy a piece of merch called a lightstick. Essentially, it is a STM32 and a mems microphone that is demodulating the carrier signal, so it can flash in time with the music. The tone has to be <ultrasonic because it has to work with consumer speakers and the mic in the device. I assume the theory goes that anyone who has been to enough concerts to have a lightstick is no longer capable of hearing the noise.
- kmeisthax 2y ago
  Alternatively the sound is in there deliberately so that if you have a lightstick it'll start playing in time with the music.
- gravescale 2y ago
  Relatedly the wristbands used at for example, Taylor Swift concerts use 38kHz IR floodlighting for the control signal. Recently HN'd: https://news.ycombinator.com/item?id=40492515 https://news.ycombinator.com/item?id=40492515
matteason 2y ago
This happened recently on Taylor Swift's rerecording of 1989 - a persistent tone at 15KHz on multiple tracks [0]. The Taylor's Version records have to be some of the most carefully-produced albums around, given that the goal is to accurately reproduce existing recordings, so it's amazing that it made the final release. [0] https://old.reddit.com/r/TaylorSwift/comments/17iv3r2/for_people_who_can_hear_the_buzzingstatic_in_1989/ https://old.reddit.com/r/TaylorSwift/comments/17iv3r2/for_pe...

amelius 2y ago

No mention of how bad this must be for dogs and other animals that can hear better than humans.

_Microft 2y ago
I always wondered the same about ultrasonic parking/proximity sensors on cars.
- HeatrayEnjoyer 2y ago
  What cars produce ultrasound? I thought radar is used.
  - matteason 2y ago
    Wikipedia says both ultrasonic and electromagnetic are used: https://en.wikipedia.org/wiki/Parking_sensor https://en.wikipedia.org/wiki/Parking_sensor One of the references is for a Mercedes system that uses ultrasound
  - buildsjets 2y ago
    Every single car from every manufacturer that has PDC sensors in the bumper, which are typically visible as 4 circular sensors on the surface of the bumper.
  - ptero 2y ago
    Most cars have ultrasonic sensors for parking and radar for longer range detection, such as cruise control.
  - ornornor 2y ago
    I hear some car alarm sensors when passing by, the ones that will trigger when someone is about to park too close and hit the armed car.
- houseplant 2y ago
  induction stovetops create extremely loud high pitched noises, some get up to 100+ decibels. You can't "hear" it but at higher heat levels you can definitely "feel" it in your ears.

hehdhdjehehegwv 2y ago

It’s been used for ads for years.

pavel_lishin 2y ago
How so?
- paulmd 2y ago
  https://en.wikipedia.org/wiki/Cross-device_tracking#Ultrasonic_tracking_2 https://en.wikipedia.org/wiki/Cross-device_tracking#Ultrason...
- xphilter 2y ago
  I brought some class actions years ago alleging the unlawful use of this tech for essentially ads purposes: https://topclassactions.com/lawsuit-settlements/lawsuit-news/golden-state-warriors-seek-dismissal-app-spying-class-action-lawsuit/ https://topclassactions.com/lawsuit-settlements/lawsuit-news... and https://www.freeadvice.com/legal/lisnr-responds-to-lawsuit-that-accuses-app-of-eavesdropping-without-consent/ https://www.freeadvice.com/legal/lisnr-responds-to-lawsuit-t...
  - Etherlord87 2y ago
    1st link: claim dismissed. 2nd link doesn't work for me (access denied).

jszymborski 2y ago

Oona's blog posts are consistently bangers; always a treat when she posts a new one.

tlb 2y ago

Has the hypothesis that this is noise from a class-D amplifier (which I assume most commercial speakers use) been eliminated? Those generally switch at MHz frequencies, but have subharmonics all over the place except the ones that have been carefully eliminated by filtering. I wouldn't be too surprised if there was a cheap brand of class-D amplifier that had a 20 kHz tone.

kurthr 2y ago
I'd also be suspicious of this. You can also get a lot of beating artifacts from having many amplifiers in close proximity. If the speakers were still larger "mid-range" horns as were seen in decades past, this also might be less of an issue (low efficiency above 10kHz), but for cost/aesthetic reasons the speakers have shrunk quite a bit so they no longer mechanically filter much. If the problem was something everyone could hear it would likely be fixed, but since it's a minority, it's likely to persist. One other possibility for active US is crowd tracking. I've seen solutions that monitor # people and walking speed at doorways using ultrasonics. A lot of "one way" doors also use simple US detectors.

instagib 2y ago

Bistatic 0. one transmitter + two receivers. Very fun topic as I worked on a few and sync them up as the transmitter radar needs to connect to the second receiver radar (usually a full radar for redundancy). Multistatic is fun also as they employ many covert receivers. Had many war game scenario conversations about the setups. Maybe they’re getting a bistatic return with multiple microphones separated in distance enough to be significant. Ultrasonic frequencies generally start at around 20,000 Hz (20 kHz) and can extend up to several gigahertz (GHz). 1 0. https://en.m.wikipedia.org/wiki/Bistatic_radar https://en.m.wikipedia.org/wiki/Bistatic_radar 1. https://www.rfcafe.com/references/general/ultrasonic-spectrum.htm https://www.rfcafe.com/references/general/ultrasonic-spectru...

fullspectrumdev 2y ago

I had almost forgotten about the “Mosquito” devices for deterring youths that became ubiquitous in some areas during the late 2000’s and early 2010’s. They were quite expensive and I know of a few people who got annoyed and specifically vandalised them due to the annoying sound.

i80and 2y ago
I'm glad those seem to have mostly faded away? The installation of them especially in spaces open to the general public has always struck me as deeply sick and antisocial
- fullspectrumdev 2y ago
  There’s still a few around where I live, way less than before though and I think it’s old installations that somehow still function instead of “net new”. What’s awfully irritating is that I can still hear them. I’m in my 30’s with pretty gnarly hearing damage, and can still hear that frequency range.
- houseplant 2y ago
  I believe they were harming birds and insects, but I don't think someone using a mosquito tone to deter human beings cares much for wildlife health
michaelcampbell 2y ago
People they were designed to keep from "hanging out" no longer "hang out" outside any more anyway.

mannyv 2y ago

Cruise ships do this. It drove my kids crazy.

doughecka 2y ago

I work for a manufacturer of PA systems, our amplifiers only do a periodic test every few minutes, one channel at a time. We measure the current the speaker circuit draws, and if that changes drastically we know something is wrong.

transpute 2y ago

> .. there's a clear Doppler shift in the reverb. The frequency shift goes from positive to negative at the same moment that the scooter passes us, seen as the wideband wheel noise changing color.. The speed of sound at 15 °C is 340 m/s. The maximum Doppler shift here seems to be 350 Hz. Plugging all these into the equation we get 11 km/h, which sounds like a realistic speed for a scooter.. Automated speed trap in the car park.. Doppler radar, https://en.wikipedia.org/wiki/Doppler_radar https://en.wikipedia.org/wiki/Doppler_radar, also applies to WiFi reflections, which can be visualized, https://www.youtube.com/watch?v=g3LT_b6K0Mc https://www.youtube.com/watch?v=g3LT_b6K0Mc. Upcoming 2024 "AI" PCs, tablets and phones with NPUs and WiFi 7 can use machine learning and doppler reflections to infer human activity in 3-D space (proximity, movement, heart rate, gestures), via IEEE 802.11bf WiFi Sensing, https://www.technologyreview.com/2024/02/27/1088154/wifi-sensing-tracking-movements/ https://www.technologyreview.com/2024/02/27/1088154/wifi-sen... > Soon, thanks to better algorithms and more standardized chip designs, [WiFi] could be invisibly monitoring our day-to-day movements for all sorts of surprising—and sometimes alarming—purposes. Yes, it could track your breathing. It could monitor for falls. It may make buildings smarter, and increase energy efficiency by tracking where people are. The flip side of this, however, is that it could also be used for any number of more nefarious purposes. Someone outside your home could potentially tell when it’s vacant, or see what you are doing inside.

skmurphy 2y ago

Very interesting. I can remember being able to hear a high pitched tone when I was 4-6 shopping with my mother in department stores that seemed to get louder when we approached flush mounted speakers in the ceiling. This article measures the frequencies and explains it's a normally operating feature of the systems.

raverbashing 2y ago
I'm not sure I ever managed to hear a 19kHz tone, but I'd say it might have been possible (or the tone was a lower frequency one). But yes the old CRT whine I could definitely hear
- skmurphy 2y ago
  I was young. My mother could not hear it and thought I was just being annoying. This is several decades ago, now I can barely hear my turn signal blinker and am preparing to emulate my father's practice of driving a few miles with his blinker on after signalling a lane change.
  - metabagel 2y ago
    One thing that can help is pressing the turn signal lever with less force than is needed to latch it. This should cause the indicator to flash three times and then stop. It’s an operating mode I wasn’t aware of for decades.
    - joecool1029 2y ago
      Not all cars do this, german car feature? (only VW's I've driven from 2000's onward seemed to have)
      - lsaferite 2y ago
        My Kia has it as well.

yard2010 2y ago

> Use it to deliver ads somehow Please don't write such things on the internet

MichaelMug 2y ago
It’s clearly written it’s an idea. I don’t know what you’re implying here.
- jfengel 2y ago
  He's saying not to give them any ideas.
ale42 2y ago
Having read this blog in the past, I imagine the author was sarcastic on this one.

ricardobeat 2y ago

Totally speculative territory, but I’ve had headaches when going to a shopping center since I was a kid. It’s infallible, one to two hours and my head is exploding. I’ve always attributed it to the noise, crowds and sensory overload but it never happens elsewhere. Could it be?

LorenPechtel 2y ago
Perfume, perhaps? There are things I'm sensitive to even though I can't actually smell them.
e40 2y ago
Smell, too. Clothes stores always smelled horrible to me and almost always gave me a headache.
Ylpertnodi 2y ago
Thanks. I thought it was just me, and circumst

cesaref 2y ago

From the description of the product, I think the intention is that the tone is received electrically at the end of a cable run, so receipt of the tone indicates continuity of the speaker cabling. This high frequency has been chosen to ensure that it is low enough to be amplified and transmitted along with the audio content, and is high enough to be attenuated by the tweeters (so little energy is transmitted), and high enough in frequency so that whatever is emitted by the tweeters will be inaudible. If this is the case, it would sound like there is no need to encode any information on the signal, just it's presence is enough to test the wiring is intact. I'm assuming this is so that if the PA is required for, say, an emergency broadcast, it is fit for purpose. The presence of a <20Khz signal would imply that it was found that in whatever installation was being used that the bandwidth of the amplifiers or some other filter was attenuating the test tone too much to be received properly, so this bodge was put in place.

deleted 2y ago

[deleted]

s1mon 2y ago

I searched the article for "occupancy" and nothing. These ultrasonic tones are most likely ultrasonic occupancy sensors used for lighting and/or security. Typically they're 25kHz or 40 kHz (i.e. out of normal human hearing range), but it's possible that they are measuring some subharmonics of the sensors. I've certainly encountered ones that have mechanical issues and will spit out frequencies that I can hear too well.

Waterluvian 2y ago

I wonder how much spectrum screaming we’re doing from the perspective of other species’ sight and sound.

Havoc 2y ago

> I might have been scrolling through the audio spectrum while waiting for the underground train; What gadget is this person using for this? And audio-y flipper one of sorts?

Marciakhan 2y ago

[dead]

incognito124 2y ago

Her blogs are always a joy to read

CliffStoll 2y ago

FM Radio transmitters broadcast a continuous 19 KHz pilot tone to indicate that it's a stereo broadcast. If it's present, then there's also a 38 KHz AM modulated carrier, which has the stereo information. The main FM modulation is (Left + Right) audio channels - the baseband. The 38 KHz subcarrier is (Left - Right). Notice that the stereo information is likely to be higher noise, being AM and without a lot of power. So on weak FM broadcast signals, you're often better off setting your tuner to mono. Some cruddy FM tuners don't properly filter out the 19Khz pilot tone, resulting in ear-ringing in the listener.

LeoPanthera 2y ago
The unfiltered pilot tone was a problem when recording FM radio onto tape, beating against the bias tone and confusing Dolby NR into thinking there was constant sound. High-end cassette decks had an "MPX Filter" which was a sharp 19kHz filter before the recording system.
- CliffStoll 2y ago
  You betcha! And FM broadcasts have a high-frequency pre-emphasis, which adds something like 10dB of boost to audio high frequencies. This is to reduce high frequency noise that occurs in analog FM systems. Radio receivers have a matching de-emphasis high-frequency cut. Indeed, both vinyl phonographs and audio tape systems employ similar pre-emphasis and de-emphasis. It's the RIAA curve for phonographs. Not sure what the standard is for mag tape.
  - bux93 2y ago
    For mag tape, it's different Dolby NR schemes.
- egorfine 2y ago
  > confusing Dolby NR Accidental DRM even before the "D" came to be.

_spduchamp 2y ago

I'd like a way to use an array of mics and do some sort of visualization and video overlay to try to see and locate the sources of these kinds of high pitch sounds.

fredthedeadhead 2y ago

What does the author use to measure sound and create those graphs? I'm interested in automatically monitoring an annoying noise that's coming from a neighbour.

EricE 2y ago
As others in the comments have already mentioned, Studio Six makes very nice Audio Tools (at least on iOS/Mac, not sure if they are also on Android). Their SMAART module is the cheapest way to get access to SMAART tools - which can be a thing in and of themselves. I use them to asses what's going on with live sound I occasionally mix. What's really nice is they calibrate fairly accurately to Apple hardware out of the box. More than accurate enough for my purposes.

lomase 2y ago

When I used to work with PA systems we had this really cool old-school looking impedance meter. We used to check the continuity of the PA like you do with a resistance meter in an electrical circuit. I dont know much about analog audio but if I am remembering correctly, the device could inject a 1Khz tone that was only heard on speakers with impedance problems. https://toa.co.id/product/zm-104a-impedance-meter https://toa.co.id/product/zm-104a-impedance-meter