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STEALTH FLYING, is it possible?

Discussion in 'Off Topic' started by PhantomFanatic, Jan 11, 2015.

  1. PhantomFanatic

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    What makes people notice our drones? The loud rotor sound.

    We, at a hobby level, can't reduce the rotors cutting through the air, sound. But, noise canceling technology has been 'out' for quite awhile now. It works best if you are wearing headphones.

    Here is how it works: Sound is a Sine wave as is our household current. Think of a straight line, with a line shaped like a perfectly round hill. Then, under the line, is an upside down hill, the same size and height of the right side up hill, then imagine that pattern continuing. You just learned what a sine wave is, somewhat!

    These noise canceling headphones use a microphone to 'listen' to the sound around the user. The electronic circuit, then produces another sine wave at the same height as the 'hills' in the other one, with one difference. The electronically produced sound is out of phase with the surrounding sound.

    Imagine the first sine wave, a straight line with an upright hill, an inverted hill, an upright hill, etc. This is the outside, of the headphone, sound or the ambient sound. Imagine another horizontal line below the first. This one has the same hill pattern, BUT when the ambient sound has an upright hill, or produced sounds to the headphones has an inverted hill. It is like adding -5 with +5. The result is 0.

    For sound waves, this means the ambient sound has been cancelled out by the generated sound, so you hear absolutely nothing! You could be operating a jackhammer and YOU would hear nothing. This isn't like putting in ear plugs, that reduces the sound. There is NO sound going to your ear drums!

    These headphones are used around loud equipment. They are also available with a built in radio or an audio input. Say you are in a subway car, you won't hear the sound of the car, nor the passengers talking. You will only hear your music or turn that off an you hear nothing. You could nap surrounded by jackhammers. But, if you wanted to do that, go to a doctor as something is very wrong with you!

    This is easy to do with headphones. It is harder to do with a speaker. This is just us brainstorming, but say you put a speaker and audio amplifier on your phantom. You produce sound at the same volume level and inverted from the rotor noise.

    There are many complications as people will be in different locations. But, I guarantee you that our military has worked out the bugs where their/our stealth helicopters make very little sound compared to without this technology. They do more than just that, they design the rotors for reduced sound.

    Maybe I'm nuts, but there is a very strong anti-drone movement. If the public can't hear our multi-rotors, they won't know to look up. Even if you don't understand how it works, what do you think about reducing your bird's noise? Any other thoughts on how to minimize the sound, besides height? Or, a way that we can see our bird, but others can't? I think that may be possible.
     
  2. kitari

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    Correct me if I'm wrong as I'm still a student, but with noise canceling headphones, you're ears are either covered or you have earbuds in your ears, which listens for external noise via a small mic on the outside of the headphones and then cancels it out using the noise canceling technology which is like you said, when it responds with an out of phase wavelength that cancels out any external noise via the outside mic. So with that said, isn't the insulation of the headphones and the external speaker the main reason the noise cancelation works? If you put a mic below each prop, and 4 small but very powerful speakers, along with the noise canceling programing, it still wouldn't work unless you could isolate the props themselves right? Just my thoughts anyways, also, I'm sure if we did manage to make our quadcopters silent, it would only give people more of an excuse to say we're spying on them. :roll:
     
  3. PhantomFanatic

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    You are absolutely correct! And, I thought I stated that in my post.

    But, this is an exercise in thought! There are so many factors, including the Doppler effect. But, I tend to think it could be helped to some degree.

    Our military has radar invisible helicopters and when they went to murder an unarmed man, they must have silenced the rotors, to some degree. I'm sure that rotor design is one part. Another is a long tube that ejects hot gasses, which via the tube, reduced the exit temperature, so heat seeking missiles will not be as effective, plus the radar deflecting technology.

    Very low flight also reduces the radar signature. BUT, I believe our military has a noise canceling system. Yes, it is much harder to noise cancel without headphones. I was thinking along the line of if you can't hear it, it won't bother you.

    Lastly, why are people offended by drones, when Google satellites and military satellites can and do see actions of citizens? Because the satellites make no noise and they aren't visable.

    However, when one sees a vapor trail in the sky, why don't they feel invaded? What about video cameras everywhere? After 911, our government no longer need a judges' signature to get a phone tap, even cell phones. Back in the operator days, that connected you to long distance numbers, well they listened in to pass the time. Yes, this is a fact as I was hooked in by a friend, one time as I didn't like snooping. She said they all did it to pass the time.

    I was thinking along the lines of reducing our impact. Sadly, I doubt any Phantom could lift the needed equipment to accomplish this. If it was possible, would you buy it? And, if I accomplished it, I would disappear forever!
     
  4. kitari

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    Well, I did a little research and I think I have a few recommendations for stealth flight. 1. increase blade pitch but slow down motor speed (probably best to start with a collective pitch quadcopter unless you know how to custom make props), 2. more blades on each prop, maybe extend/widen them to get more lift with less rotor spin, and 3. Use military paint (Actually don't do that, it'll block radar, but would probably block all signals including your tx and especially gps.) All my info is based on a few of the ways stealth helicopters reduce noise, but you probably already knew about these things since I'm sure you've been doing this type of thing for a while now. lol

    So anyways, with that said, I think it would be an interesting project. Also, our school has been trying to get a drone program together for about 2 years now, and I'm the ONLY person in my school that really plays around with them. Maybe I'll be able to figure these things out and start up a new program for my class. There's only 2 people in my group, so this isn't going to be easy, but either way I think it'll be interesting to try. I'll be sure to update you if I find out anything.

    Oh, and as for why people are offended by drones, I think it's just because it's a new technology that people don't understand yet. Plus you have the media constantly talking about all the people trying to spy on people or how these evil drones can just flyaway or fall from the sky and kill people yada yada yada, and then there's the group of people who think the illuminati's about to take over and robots are about to wipe out humanity or something like that. I think that if I did somehow manage to figure out how to make drones, a class on them would be a wonderful idea. I could show people how to make them as well as inform them about all the rules/regulations, safety tips, and so on with the help of the people here at phantom pilots of course!

    One last thing, if you ever figure the stealth quadcopter thing out, I'd buy one. (if the wife lets me) :lol:
     
  5. SteveMann

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    Luxury cars have been for a few years using active noise reduction (ANR) to make the inside of their cars sound quieter.
    To generate an ANR field around your drone would require significant audio power that would require a system that outweighs your Phantom by a wide margin.
    My 3DR hex has ten-inch props and the motors are slower than the Phantom (I would need to look up the kv ratings) and it can lift three pounds, but is significantly quieter than the Phantom.
     
  6. rexster314

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    Exception taken to the statement "Our military has radar invisible helicopters and when they went to murder an unarmed man," and hoping those helicopters get sent out on more missions to do the same thing
     
  7. PhantomFanatic

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    Yep Steve, I forgot to mention that. But, again, it is a sealed system.
     
  8. PhantomFanatic

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    The statement is correct. He did not have a gun in his hand, according to our military. Our country uses propaganda too. They didn't want a court trial. Did he really do all that we were told? We will never know, now.

    Did Iraq really have weapons of mass destruction? No. Were all of the murdered citizens trying to escape, on that road, responsible for 911? Our country wanted someone to blame for 911 and our government gave us Iraq and Afganistan and anywhere else they desire, in the future.

    Watch "911, Loose Change" on Netflix. I watched because there wasn't much on that night. At the very least, it is an exercise in thought.
     
  9. PhantomFanatic

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    You make some good points. Before I started this thread, I knew it would be impractical to carry all the required equipment on a Phantom. One way our military works around noticeable sound is to increase altitude. That works for us too. I'll abide by our 400' rule, but higher photography really would appeal to me. Maybe I just need a government surplus weather balloon. But, you are supposed to go through the channels, to even do that.

    I'm far from an expert on the paint that the military uses, but I think it only helps absorb radar along with angular structures that won't reflect radar back to the point it is transmitted from. But, I doubt that it would affect RF signals and GPS.
     
  10. kitari

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    I have another idea for the stealth flying project! what about those bladeless fans? If you could create enough lift with those things, you could use those to replace props and that could make it very quiet since you won't have props chopping though the wind making all that noise. I could also be completely wrong, but it sounds good at least. :) (I think this has went beyond things you can do to the phantom, and went to ideas for a scratch build lol)
     
  11. crash1sttime

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    Dont go giving James Dyson anymore bloody ideas :lol:
     
  12. PhantomFanatic

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    Very little air flow = no lift! :)
     
  13. LGM30G

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    Ishould not have done this search(stealth phantom) took all the fun out of the thought,lol OSI in the house.
     
  14. IflyinWY

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    There is a great deal that can be done with the shape of the blades on the Phantom to reduce noise. ;) It would be more of a hum with wide blades. Efficiency would go downhill pretty quick.

    And we are just brainstorming here, right?
    There's no reason for the trolls to stop by and turn this into a crap thread, right?
     
  15. Fplvert

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    Sorry, IflyinWY,

    We have new mods to take care of that.

    image.jpg
    Just had to.
     
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  16. dirkclod

    dirkclod Moderator
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    :eek:
     
  17. Fplvert

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    Not better?:rolleyes:

    I don't get these new emoticons!:confused:
     
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  18. dirkclod

    dirkclod Moderator
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    Which one's ...where .. crazy_frog_looking_animated_avatar_100x100_92893.gif
     
  19. IflyinWY

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    They are pretty lame.
    I like Dirks... Ya Got Em Good.gif
     
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  20. Fplvert

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    image.jpg
    Sorry, I interrupted a serious discussion. I'll go to the back off the class.:oops:
     
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