10 ms·

One thing the drones really need to do before being deployed en masse (besides safety) is to become relatively silent. They are quite loud. I can hear a single

by cronix 8y ago

One thing the drones really need to do before being deployed en masse (besides safety) is to become relatively silent. They are quite loud. I can hear a single one from about 1/2 mile away. I can't imagine what it will be like if many are flying all over, at all times. It will be like everybody is living next to an airport - something I consciously choose to not live close to due to noise pollution. Quality of life will go down, and people will become very annoyed. I own 2 drones. They are very loud and there isn't much you can do to quiet them. They are helicopters with 4x the number of blades on very tiny motors that spin very fast and are loud.

neaanopri 8y ago
I don't see this happening. The propeller physics aren't changing. If you are using the quadrotor architechure, directly lifting your playload with no wings, there's a sound-per-kg number that can't be engineered away.
- iancmceachern 8y ago
  Is Active noise canceling an option?
  - toufiqbarhamov 8y ago
    On the ground? To an extent, but it would be expensive to deploy and maintain. On the drone? No, you’re adding weight and reducing available power.
    - jstplanecurious 8y ago
      I thought iancmceachern asked a really good question. I was curious if it could work even theoretically. I read the Wikipedia article on Active Noise Control. The third paragraph under Explanation: https://en.wikipedia.org/wiki/Active_noise_control#Explanation https://en.wikipedia.org/wiki/Active_noise_control#Explanati... mentions that if it's at the source, it needs to be just as loud as the source (as opposed to being by the ear, in which case even a whisper might be enough). In addition to being as loud as the source, you need to blast it in all directions. So I guess it's hard/impossible to perfectly hit the same sound waves in all directions. If you ever miss, you'll just be doubling the noise. Maybe that's why you'll be hard-pressed to find anything in a fixed installation that uses active noise cancellation at the source - even if it's heavy, periodic, and uses a lot of power anyway - such as a home air conditioner. Noise cancellation close to the ear seems much easier for this reason, and maybe at the source it's just impossible.
      - toufiqbarhamov 8y ago
        Not impossible, just impractical unless silence is incredibly important. If you want a quiet helicopter then you do what you can to reduce the noise signiture, then you might consider destructive interference. You wouldn’t use speakers, but that’s not the only way to produce a noise. In fact a clever country might even figure out how to use an arrangement of blades and fans designed to produce noise in such a way that it tends to cancel out the loudest contributions to the signature. Buuuut... that’s not really viable for anything civilian or even commercial.
        odorousrex 8y ago
        Like the Stealth Black Hawk helicopters that were used in the Osama Bin Laden raid! (There existence is still not officially acknowledged of course, but many pictures exist.) I was very curious about the technology they used to reduce the noise, as black hawks are very loud.
      - icebraining 8y ago
        I believe I read that fan noise is chaotic, and hence impossible to cancel. Don't quote me on that, though.
  - objektif 8y ago
    This right here sounds like overengineering.
  - usrusr 8y ago
    Active noise canceling is equivalent to beam shaping. It can work in headphones because you can aim the minima at the ear and the maxima away from it, but the best you could achieve by adding speakers to a drone would be selecting where the energy hits. Directing everything to the upper hemisphere would be nice, but that's not how beam shaping works.
- hoaw 8y ago
  Elon Musk had a similar argument against, I think, flying cars on Joe Rogans show. I guess it is one of those things were imagination is greater than reality. Like a lot of space stuff (mostly in regards to distance). Though I guess high and light applications would disturbe less.
- deleted 8y ago
  [deleted]
- mikeash 8y ago
  What makes a propellor different from a wing in this respect? Is it just because you have several of them next to each other and interfering with each other?
  - mediaman 8y ago
    Both propellers and wings are fundamentally the same thing: airfoils. However, air passes over a propeller much, much faster than over a wing, and creates shock waves in a way that wings don't.
    - mikeash 8y ago
      Does it? The same airfoil needs the same speed to provide a given amount of lift, regardless of whether it’s a wing or a propellor.
      - alexis_fr 8y ago
        The speed of a propeller is low close to the rotor, and sometimes faster than sound at the extremity of the blades. Can’t reduce sound on that.
        sokoloff 8y ago
        Propeller efficiency takes a nose dive when the tips go supersonic. Most props therefore do not operate in this range.
    - Gibbon1 8y ago
      Wings don't rotate and thus don't efficiently produce sound waves.
  - toufiqbarhamov 8y ago
    It’s a combination of factors, one of which is that a prop is just out there, unshielded like the fans inside a jet engine (which still make a ton of noise in the case I’d high bypass models). Then there’s cortex shedding, which is mostly occurring along edges and tips. Airplanes also tend to fly at much higher altitudes except on takeoff and landing, or their noise would be an issue too. Finally you’re right that the number and arrangement of blades matters, because each blade produces some turbulence, vortices, etc which then interact with the next blade in sequence. All told the issue is just s high degree of aerodynamic noise. You get that with a wing and any aerodynamic body, and really if you’ve ever seen model jets fly you’ve heard the racket they make. The major issue is that until drones came around, you didn’t have to worry very often about large number of high performance aircraft operating throughout civilian airspace, at very low altitudes in crowded areas.
bigmattystyles 8y ago
Tangent: I don’t think I’ve ever been more incensed than when I learned Harley Davidsons are quiet out of the factory and people make them loud. And while I can get a ticket for something trivial, I’ve never heard of someone getting a ticket for riding a motorcycle or car that’s obnoxiously loud and can be heard a mile away. My point, I guess, cities, townships, what have you, don’t care about noise.
- reaperducer 8y ago
  My point, I guess, cities, townships, what have you, don’t care about noise. Cities, townships, what have you, will care about whatever their active constituents tell them to. It took a few years, but a neighborhood organization managed to get a crackdown on motorcycle noise in Chicago. I don't know if it worked because I moved away before it went into effect. But there was a ton of press coverage for a very long time, so there's no way the offending riders could know that people don't like them. Loud Motorcycles In Alderman's Crosshairs As LSD Noise Monitoring Starts: https://www.dnainfo.com/chicago/20170824/lincoln-park/loud-motorcycles-aldermans-crosshairs-as-lsd-noise-monitoring-starts/ https://www.dnainfo.com/chicago/20170824/lincoln-park/loud-m...
  - mbrumlow 8y ago
    > My point, I guess, cities, townships, what have you, don’t care about noise. I think the poster was referring to active constituents. But I think you are wrong. I don't know of anybody who wants a loud car or bike trekking by their house. But yet it still happens over and over. It is unclear if enough "active constituents" are not complaining or they are ignored.
    - cm2187 8y ago
      I don't but I know some people are delighted at the sound of some sport cars.
      - reaperducer 8y ago
clay_the_ripper 8y ago
Yes! My biggest single complaint about drones is the noise. I also own and fly a drone (for professional photography and video work) but I am LOATHE to fly that thing when anyone else is around. It’s just so dang annoying. As a drone owner, it drives me bananas when I see people just flying them all over the place with no account for how irritating the noise is. If drones could be made substantially quieter, everyone’s quality of life would go up and we could be saved from inconsiderate people with no regard for others.
- deleted 8y ago
  [deleted]
- brokenmachine 8y ago
  I honestly wish all drone owners were as considerate as you sound. Unfortunately, anecdotally I'd have to say that the majority are not considerate.
  - clay_the_ripper 8y ago
    Yeah that’s the dream alright. So many of them are so incredibly inconsiderate that it gives the rest of us a bad name. I’m legitimately too embarrassed to fly it around anyone because of how incredibly inconsiderate your average hobbyist is. Even though I actually have a reason to fly it (I get paid).
sierdolij 8y ago
This doesn't really need another law. If something can be heard X m/ft away after night-time N (i.e., car stereo bass blasting at 3 am), or louder than Y anytime (i.e., concert without a permit), then it's creating a nuisance under existing legislation. It needs enforcement of what's already on the books if there's a complaint. And the permit requirement to operate a small R/C toy is ridiculous: this information you don't want the government to have because it will be misused similarly to how social media was abused in the Gatwick Airport (non-)incident. The sensible thing would be classes (Class 1, 2, 3, etc.) of unmanned flying devices, as with model rockets. https://www.nar.org/find-a-local-club/section-guidebook/laws-regulations/ https://www.nar.org/find-a-local-club/section-guidebook/laws...
- michaelt 8y ago
  It needs enforcement of what's already on the books if there's a complaint. Do the cops in your area respond to a noise complaint in less than the ~15 minutes it takes for a drone battery to run out?
fourTimes 8y ago
helicopters with 4x the number of blades I mean, what’s the difference between a helicopter with four blades, versus the same helicopter by with only one blade, but four times the size? Except a full scale helicopter blade is easily 100 times larger. So they are helicopters, but 100 times smaller, but with four blades.
amelius 8y ago
I guess army drones are silent.
- michaelt 8y ago
  Army drones are usually fixed-wing - in the civilian market they'd be called "RC planes". RC planes are less popular than quadcopters for hobby use, as it takes a lot more skill to avoid crashing them.
aedron 8y ago
Maybe if they fly them high enough? Or maybe wind would become a problem. Also, dedicated drone corridors that are over roads or uninhabited areas, so at least only cars would be hit in case one of them drops out of the sky.
darkpuma 8y ago
The solution is fixed wing "drones". The props on a fixed wing RC 'drone' are still loud, but for an equivalent mass in the air they are a LOT quieter than quads. They're also more efficient, you get more flight time with fixed wings. There are just three problems: 1) Landing space (not a hard problem to solve with durable designs that have very low stall speeds.) 2) For some photography purposes, hovering is the only way to get the shot. 3) They're just not as sexy. People like quads because they seem a lot more sci-fi.
iambateman 8y ago
When I flew a Phantom 4 to 150 feet, it was basically invisible and totally silent. I’m guessing you’re thinking of much larger drones?

by cronix 8y ago

neaanopri 8y ago

I don't see this happening. The propeller physics aren't changing. If you are using the quadrotor architechure, directly lifting your playload with no wings, there's a sound-per-kg number that can't be engineered away.

iancmceachern 8y ago
Is Active noise canceling an option?
- toufiqbarhamov 8y ago
  On the ground? To an extent, but it would be expensive to deploy and maintain. On the drone? No, you’re adding weight and reducing available power.
  - jstplanecurious 8y ago
    I thought iancmceachern asked a really good question. I was curious if it could work even theoretically. I read the Wikipedia article on Active Noise Control. The third paragraph under Explanation: https://en.wikipedia.org/wiki/Active_noise_control#Explanation https://en.wikipedia.org/wiki/Active_noise_control#Explanati... mentions that if it's at the source, it needs to be just as loud as the source (as opposed to being by the ear, in which case even a whisper might be enough). In addition to being as loud as the source, you need to blast it in all directions. So I guess it's hard/impossible to perfectly hit the same sound waves in all directions. If you ever miss, you'll just be doubling the noise. Maybe that's why you'll be hard-pressed to find anything in a fixed installation that uses active noise cancellation at the source - even if it's heavy, periodic, and uses a lot of power anyway - such as a home air conditioner. Noise cancellation close to the ear seems much easier for this reason, and maybe at the source it's just impossible.
    - toufiqbarhamov 8y ago
      Not impossible, just impractical unless silence is incredibly important. If you want a quiet helicopter then you do what you can to reduce the noise signiture, then you might consider destructive interference. You wouldn’t use speakers, but that’s not the only way to produce a noise. In fact a clever country might even figure out how to use an arrangement of blades and fans designed to produce noise in such a way that it tends to cancel out the loudest contributions to the signature. Buuuut... that’s not really viable for anything civilian or even commercial.
      - odorousrex 8y ago
        Like the Stealth Black Hawk helicopters that were used in the Osama Bin Laden raid! (There existence is still not officially acknowledged of course, but many pictures exist.) I was very curious about the technology they used to reduce the noise, as black hawks are very loud.
    - icebraining 8y ago
      I believe I read that fan noise is chaotic, and hence impossible to cancel. Don't quote me on that, though.
- objektif 8y ago
  This right here sounds like overengineering.
- usrusr 8y ago
  Active noise canceling is equivalent to beam shaping. It can work in headphones because you can aim the minima at the ear and the maxima away from it, but the best you could achieve by adding speakers to a drone would be selecting where the energy hits. Directing everything to the upper hemisphere would be nice, but that's not how beam shaping works.
hoaw 8y ago
Elon Musk had a similar argument against, I think, flying cars on Joe Rogans show. I guess it is one of those things were imagination is greater than reality. Like a lot of space stuff (mostly in regards to distance). Though I guess high and light applications would disturbe less.
deleted 8y ago
[deleted]
mikeash 8y ago
What makes a propellor different from a wing in this respect? Is it just because you have several of them next to each other and interfering with each other?
- mediaman 8y ago
  Both propellers and wings are fundamentally the same thing: airfoils. However, air passes over a propeller much, much faster than over a wing, and creates shock waves in a way that wings don't.
  - mikeash 8y ago
    Does it? The same airfoil needs the same speed to provide a given amount of lift, regardless of whether it’s a wing or a propellor.
    - alexis_fr 8y ago
      The speed of a propeller is low close to the rotor, and sometimes faster than sound at the extremity of the blades. Can’t reduce sound on that.
      - sokoloff 8y ago
        Propeller efficiency takes a nose dive when the tips go supersonic. Most props therefore do not operate in this range.
  - Gibbon1 8y ago
    Wings don't rotate and thus don't efficiently produce sound waves.
- toufiqbarhamov 8y ago
  It’s a combination of factors, one of which is that a prop is just out there, unshielded like the fans inside a jet engine (which still make a ton of noise in the case I’d high bypass models). Then there’s cortex shedding, which is mostly occurring along edges and tips. Airplanes also tend to fly at much higher altitudes except on takeoff and landing, or their noise would be an issue too. Finally you’re right that the number and arrangement of blades matters, because each blade produces some turbulence, vortices, etc which then interact with the next blade in sequence. All told the issue is just s high degree of aerodynamic noise. You get that with a wing and any aerodynamic body, and really if you’ve ever seen model jets fly you’ve heard the racket they make. The major issue is that until drones came around, you didn’t have to worry very often about large number of high performance aircraft operating throughout civilian airspace, at very low altitudes in crowded areas.

bigmattystyles 8y ago

Tangent: I don’t think I’ve ever been more incensed than when I learned Harley Davidsons are quiet out of the factory and people make them loud. And while I can get a ticket for something trivial, I’ve never heard of someone getting a ticket for riding a motorcycle or car that’s obnoxiously loud and can be heard a mile away. My point, I guess, cities, townships, what have you, don’t care about noise.

reaperducer 8y ago
My point, I guess, cities, townships, what have you, don’t care about noise. Cities, townships, what have you, will care about whatever their active constituents tell them to. It took a few years, but a neighborhood organization managed to get a crackdown on motorcycle noise in Chicago. I don't know if it worked because I moved away before it went into effect. But there was a ton of press coverage for a very long time, so there's no way the offending riders could know that people don't like them. Loud Motorcycles In Alderman's Crosshairs As LSD Noise Monitoring Starts: https://www.dnainfo.com/chicago/20170824/lincoln-park/loud-motorcycles-aldermans-crosshairs-as-lsd-noise-monitoring-starts/ https://www.dnainfo.com/chicago/20170824/lincoln-park/loud-m...
- mbrumlow 8y ago
  > My point, I guess, cities, townships, what have you, don’t care about noise. I think the poster was referring to active constituents. But I think you are wrong. I don't know of anybody who wants a loud car or bike trekking by their house. But yet it still happens over and over. It is unclear if enough "active constituents" are not complaining or they are ignored.
  - cm2187 8y ago
    I don't but I know some people are delighted at the sound of some sport cars.
    - reaperducer 8y ago

clay_the_ripper 8y ago

Yes! My biggest single complaint about drones is the noise. I also own and fly a drone (for professional photography and video work) but I am LOATHE to fly that thing when anyone else is around. It’s just so dang annoying. As a drone owner, it drives me bananas when I see people just flying them all over the place with no account for how irritating the noise is. If drones could be made substantially quieter, everyone’s quality of life would go up and we could be saved from inconsiderate people with no regard for others.

deleted 8y ago
[deleted]
brokenmachine 8y ago
I honestly wish all drone owners were as considerate as you sound. Unfortunately, anecdotally I'd have to say that the majority are not considerate.
- clay_the_ripper 8y ago
  Yeah that’s the dream alright. So many of them are so incredibly inconsiderate that it gives the rest of us a bad name. I’m legitimately too embarrassed to fly it around anyone because of how incredibly inconsiderate your average hobbyist is. Even though I actually have a reason to fly it (I get paid).

sierdolij 8y ago

This doesn't really need another law. If something can be heard X m/ft away after night-time N (i.e., car stereo bass blasting at 3 am), or louder than Y anytime (i.e., concert without a permit), then it's creating a nuisance under existing legislation. It needs enforcement of what's already on the books if there's a complaint. And the permit requirement to operate a small R/C toy is ridiculous: this information you don't want the government to have because it will be misused similarly to how social media was abused in the Gatwick Airport (non-)incident. The sensible thing would be classes (Class 1, 2, 3, etc.) of unmanned flying devices, as with model rockets. https://www.nar.org/find-a-local-club/section-guidebook/laws-regulations/ https://www.nar.org/find-a-local-club/section-guidebook/laws...

michaelt 8y ago
It needs enforcement of what's already on the books if there's a complaint. Do the cops in your area respond to a noise complaint in less than the ~15 minutes it takes for a drone battery to run out?

fourTimes 8y ago

helicopters with 4x the number of blades I mean, what’s the difference between a helicopter with four blades, versus the same helicopter by with only one blade, but four times the size? Except a full scale helicopter blade is easily 100 times larger. So they are helicopters, but 100 times smaller, but with four blades.

amelius 8y ago

I guess army drones are silent.

michaelt 8y ago
Army drones are usually fixed-wing - in the civilian market they'd be called "RC planes". RC planes are less popular than quadcopters for hobby use, as it takes a lot more skill to avoid crashing them.

aedron 8y ago

Maybe if they fly them high enough? Or maybe wind would become a problem. Also, dedicated drone corridors that are over roads or uninhabited areas, so at least only cars would be hit in case one of them drops out of the sky.

darkpuma 8y ago

The solution is fixed wing "drones". The props on a fixed wing RC 'drone' are still loud, but for an equivalent mass in the air they are a LOT quieter than quads. They're also more efficient, you get more flight time with fixed wings. There are just three problems: 1) Landing space (not a hard problem to solve with durable designs that have very low stall speeds.) 2) For some photography purposes, hovering is the only way to get the shot. 3) They're just not as sexy. People like quads because they seem a lot more sci-fi.

iambateman 8y ago

When I flew a Phantom 4 to 150 feet, it was basically invisible and totally silent. I’m guessing you’re thinking of much larger drones?