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Ultrasonic investigations in shopping centres

windytan.com

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Re: Ultrasonic investigations in shopping centres

#51

Post by imabotbeep2937 »

raverbashing wrote: post #45
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'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've been tested to 22+kHz, autistic, and older. It was the worst era.

Some of the awful roars of noise I've heard while older people called me a weirdo. CRTs, early checkout scanners, some audio systems.

And back when "as seen on TV" electronic dog whistle trainers were all the rage? Torture.

Re: Ultrasonic investigations in shopping centres

#52

Post by immibis »

h2odragon wrote: post #14
immibis wrote: post #9

Earlier quoted context omitted.

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.

It doesn't matter what your microphone can do, because your sound card does the filtering and digitization.

Re: Ultrasonic investigations in shopping centres

#53

Post by gocartStatue »

jimmaswell wrote: post #48
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'm 30 with mild tinnitus and listen to music too loud but I can still hear CRT whine too, go figure.

Wait, people regularly just don’t hear it?

Re: Ultrasonic investigations in shopping centres

#55

Post by ricardobeat »

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?

Re: Ultrasonic investigations in shopping centres

#56

Post by mrob »

matteason wrote: post #17
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.

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_pe...

It's surprisingly common in older music. I assume it's because recording studios used to run SD CRTs and everybody working there had already lost their high-frequency hearing. A 15.68kHz (mid way between PAL and NTSC horizontal refresh frequencies to remove both of them) notch filter fixes the problem in most cases.

Re: Ultrasonic investigations in shopping centres

#58

Post by houseplant »

i80and wrote: post #33
fullspectrumdev wrote: post #32

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.

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

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

Re: Ultrasonic investigations in shopping centres

#59

Post by ornornor »

abdulhaq wrote: post #42
ryandrake wrote: post #40

Earlier quoted context omitted.

Whenever my daughter puts on recent pop music, I can tell instantly. Every pop song singer seems to have their voices artificially boosted into one or two higher harmonics. It's hard to describe in words but instead of the singer singing a single note, it's as if she (and it's very evident with female singers) has some very, very high pitched harmony automatically added, which lasts the whole song. It's not like a si…

it's autotune

What a plague this thing is :(

Re: Ultrasonic investigations in shopping centres

#60

Post by ornornor »

HeatrayEnjoyer wrote: post #15
_Microft wrote: post #8

Earlier quoted context omitted.

I always wondered the same about ultrasonic parking/proximity sensors on cars.

What cars produce ultrasound? I thought radar is used.

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.
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