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Ultrasonic investigations in shopping centres
11–20 of 145 posts
Re: Ultrasonic investigations in shopping centres
#12I 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…
> 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...
> but then you'll be constantly tempted by better...
this is a likely outcome for any new hobby
Re: Ultrasonic investigations in shopping centres
#13I 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…
> 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...
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)
Re: Ultrasonic investigations in shopping centres
#14Earlier quoted context omitted.
> 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...
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.
Re: Ultrasonic investigations in shopping centres
#15Re: Ultrasonic investigations in shopping centres
#16Oona's blog posts are consistently bangers; always a treat when she posts a new one.
Re: Ultrasonic investigations in shopping centres
#17Have 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...
Re: Ultrasonic investigations in shopping centres
#18I 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.
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.
Re: Ultrasonic investigations in shopping centres
#19Earlier quoted context omitted.
I always wondered the same about ultrasonic parking/proximity sensors on cars.
What cars produce ultrasound? I thought radar is used.
Wikipedia says both ultrasonic and electromagnetic are used: https://en.wikipedia.org/wiki/Parking_sensor
One of the references is for a Mercedes system that uses ultrasound
Re: Ultrasonic investigations in shopping centres
#20It’s been used for ads for years.
How so?