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Ultrasonic investigations in shopping centres

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Re: Ultrasonic investigations in shopping centres

#81

Post by pants2 »

GolDDranks wrote: post #2

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 v…

You almost certainly want some sort of Audiomoth. They record at up to 380kHz and have all sorts of useful tooling.

Re: Ultrasonic investigations in shopping centres

#82

Post by joecool1029 »

metabagel wrote: post #71
skmurphy wrote: post #46

Earlier quoted context omitted.

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.

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.

Not all cars do this, german car feature? (only VW's I've driven from 2000's onward seemed to have)

Re: Ultrasonic investigations in shopping centres

#83

Post by mateus1 »

skmurphy wrote: post #44

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.

I wonder how much of this sound pollution disproportionately affects autistic people. We need to make our soundscapes accessible.

Re: Ultrasonic investigations in shopping centres

#84

Post by CliffStoll »

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.

Re: Ultrasonic investigations in shopping centres

#85

Post by korhojoa »

mateus1 wrote: post #83
skmurphy wrote: post #44

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.

I wonder how much of this sound pollution disproportionately affects autistic people. We need to make our soundscapes accessible.

Now if the same could be done for bad LED lighting. I hate being somewhere where the whole room is strobing at 100 hz.

Re: Ultrasonic investigations in shopping centres

#86

Post by treflop »

skmurphy wrote: post #46
raverbashing wrote: post #45

Earlier quoted context omitted.

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

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.

Long ago I made a conscious effort to turn off my blinker when I’m halfway into the next lane and now turn signals are like entirely subconscious for me.

Re: Ultrasonic investigations in shopping centres

#87

Post by LeoPanthera »

CliffStoll wrote: post #84

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.…

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.

Re: Ultrasonic investigations in shopping centres

#88

Post by gravescale »

liminalsunset wrote: post #10
spondylosaurus wrote: post #5

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.

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 rea…

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

Re: Ultrasonic investigations in shopping centres

#89

Post by deinonychus »

modeless wrote: post #4
GolDDranks wrote: post #2

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 v…

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.

I heard a pretty bad mosquito noise in a garage in Shibuya that I guessed was to shoo away smokers. It worked on me and I didn’t return.

Re: Ultrasonic investigations in shopping centres

#90

Post by bradknowles »

skmurphy wrote: post #44

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.

Going into Sears used to drive me nuts. My parents finally accepted that I was actually hearing something that they couldn’t, but it took a while.

I don’t know if it was the loss prevention system that was doing it, or what. All I could do was localize it down to being anywhere remotely close to the entrances. And the closer you got, the louder it got.

These days, my tinnitus is constantly ringing at about that same frequency. So, I would probably never be able to hear it again.

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