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I'm worried about the noise. The blades spin many times faster than a regular windmill. I imagine it will sound similar to a small plane flying very close to the ground. Of course a plane flies over once and it's gone; this thing will produce a constant droning noise that fluctuates in pitch and volume every few seconds as the kite goes up and down. If you put them far offshore this wouldn't be a problem, but I wouldn't want one of these near my house.

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The majority of noise you hear from a small prop plane flying above is from the engine.

Also, the advanced height they're trying to achieve limits the amount of noise relative to what you would hear from a small drone overhead.

I'm sceptical that that's true. We can put mufflers on gas engines to make them quieter. The prop, though, is moving a lot of air, and there's no way to get around that and have it still work.

I found an old JPL document detailing "Aerodynamic Noise from Rotors, Propellers, and Lift Fans" (http://cafefoundation.org/v2/pdf_tech/Noise.Technologies/NAS...) which has some interesting details.

A 300hp hub, spinning a 9ft diameter propeller at 1584 RPM should be roughly 72dB as measured from 1,000 feet. From a mile away, it will be more like 57dB or about TV volume from 6 feet away. -- Then again, these are spinning far faster than you'd expect from a wind turbine.

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