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I misread the title somewhat and now got a «bright» idea: Why not put noise-canceling loudspeakers on plazas? No idea whether this really would work, but I thin

I misread the title somewhat and now got a «bright» idea: Why not put noise-canceling loudspeakers on plazas? No idea whether this really would work, but I think we should explore a technical solution. Because people need a place to let off steam. A possible double win? Edit: I googled and found this: https://physics.stackexchange.com/questions/87833/outdoor-active-noise-canceling-speaker#93420 https://physics.stackexchange.com/questions/87833/outdoor-ac... -- it seems that there are limits of physics which make such noise-canceling loudspeakers infeasible. It's a pity.

kristiandupont 8y ago
Hah, my idea was "ok, so the sensors will shush people? Like play some audio? That seems a bit odd but maybe it could work?" Come think of it, this is not the first time I've gone through the whole evaluating idea-thought process and even sometimes reaching "I can't believe nobody thought of this before!" before realizing that I read something into a title that wasn't there.
- ghaff 8y ago
  It's sort of been done. https://en.wikipedia.org/wiki/The_Mosquito https://en.wikipedia.org/wiki/The_Mosquito Basically in areas where loitering by teenagers is perceived to be a problem, playing a high frequency sound tends to be unpleasant to them while older folks often don't hear it.
buro9 8y ago
Your edit got there before I did :) I live in a high-rise next to a motorway in London and at 3am I can measure the noise as 60-70db using a mobile phone noise meter (inaccurate but indicative). I investigated the feasibility of using my stereo speakers as noise-cancelling for the room... mics on the window sills and the speakers to reduce the noise in the room. I figured it would work well enough to remove the constant background hum of the road. I was wrong. It doesn't really work, and it is just noise upon noise. The best I've managed to do is hang materials inside of the windows (quilts, sheets) and have been able to knock off just under 10db of noise in the best case (when it's just the drone of vehicle volume rather than specific engines or sirens). The downside is that my high-rise is a high fire-risk tower block and I'm trading one life affecting issue (noise pollution) for another (fire risk) as now I have flammable materials inside my windows. Hard to know which affects sleep more, certainly the noise is the most real and present issue.
- grandinj 8y ago
  Noise cancellation can be a little tricky depending in the frequency. Low frequencies are easiest. Trying feeding the signal through your PC and adjusting the delay, using different delay for different frequency ranges. Some nice thick shag pile carpets, and wall-hung rugs will also help. If you like posters or pictures, consider using a block frame and putting some sound adsorbent material between the paper and the wall. Double glazed windows are your best bet, but probably quite hard to install in a high rise. Ideally you want the ones where each glass layer is a slightly different thickness. Otherwise get some custom fit earplugs from an audiologist, if it's just sleeping that is a problem. They can even fine tune them, so that voice frequencies pass through, but other frequencies are blocked.
  - buro9 8y ago
    More likely to get a pair of these https://www.bose.com/en_us/products/headphones/noise_masking_sleepbuds/noise-masking-sleepbuds.html https://www.bose.com/en_us/products/headphones/noise_masking... Though stopping or masking all noise carries risk by itself... being unable to hear what fire alarms we do have.
    - ghaff 8y ago
      Assuming these are roughly equivalent to their in-ear headphones, I wouldn't worry about missing a fire alarm. They're pretty effective, especially for low frequency noise like aircraft engines, but they're a very long way from blocking all sounds.
      - sigstoat 8y ago
        the sleep pods are a combination of average ear plugs, and tiny little speakers playing white-ish noise rather loud. they don't do any active noise cancellation. sounds like they'll be good for somewhere around 90dB of noise masking. still doubt they'd stop a fire alarm.
        8y ago

kristiandupont 8y ago

Hah, my idea was "ok, so the sensors will shush people? Like play some audio? That seems a bit odd but maybe it could work?" Come think of it, this is not the first time I've gone through the whole evaluating idea-thought process and even sometimes reaching "I can't believe nobody thought of this before!" before realizing that I read something into a title that wasn't there.

ghaff 8y ago
It's sort of been done. https://en.wikipedia.org/wiki/The_Mosquito https://en.wikipedia.org/wiki/The_Mosquito Basically in areas where loitering by teenagers is perceived to be a problem, playing a high frequency sound tends to be unpleasant to them while older folks often don't hear it.

buro9 8y ago

Your edit got there before I did :) I live in a high-rise next to a motorway in London and at 3am I can measure the noise as 60-70db using a mobile phone noise meter (inaccurate but indicative). I investigated the feasibility of using my stereo speakers as noise-cancelling for the room... mics on the window sills and the speakers to reduce the noise in the room. I figured it would work well enough to remove the constant background hum of the road. I was wrong. It doesn't really work, and it is just noise upon noise. The best I've managed to do is hang materials inside of the windows (quilts, sheets) and have been able to knock off just under 10db of noise in the best case (when it's just the drone of vehicle volume rather than specific engines or sirens). The downside is that my high-rise is a high fire-risk tower block and I'm trading one life affecting issue (noise pollution) for another (fire risk) as now I have flammable materials inside my windows. Hard to know which affects sleep more, certainly the noise is the most real and present issue.

grandinj 8y ago
Noise cancellation can be a little tricky depending in the frequency. Low frequencies are easiest. Trying feeding the signal through your PC and adjusting the delay, using different delay for different frequency ranges. Some nice thick shag pile carpets, and wall-hung rugs will also help. If you like posters or pictures, consider using a block frame and putting some sound adsorbent material between the paper and the wall. Double glazed windows are your best bet, but probably quite hard to install in a high rise. Ideally you want the ones where each glass layer is a slightly different thickness. Otherwise get some custom fit earplugs from an audiologist, if it's just sleeping that is a problem. They can even fine tune them, so that voice frequencies pass through, but other frequencies are blocked.
- buro9 8y ago
  More likely to get a pair of these https://www.bose.com/en_us/products/headphones/noise_masking_sleepbuds/noise-masking-sleepbuds.html https://www.bose.com/en_us/products/headphones/noise_masking... Though stopping or masking all noise carries risk by itself... being unable to hear what fire alarms we do have.
  - ghaff 8y ago
    Assuming these are roughly equivalent to their in-ear headphones, I wouldn't worry about missing a fire alarm. They're pretty effective, especially for low frequency noise like aircraft engines, but they're a very long way from blocking all sounds.
    - sigstoat 8y ago
      the sleep pods are a combination of average ear plugs, and tiny little speakers playing white-ish noise rather loud. they don't do any active noise cancellation. sounds like they'll be good for somewhere around 90dB of noise masking. still doubt they'd stop a fire alarm.
      - 8y ago