My five inch is, hands down, my loudest quad. There is a lot of variation between props, but as a rule I have found it to be obnoxious no matter what. I have found the stiffer the props, the louder they tend to be as there is more bite at higher RPMs.

I tested my quad outside at a parking lot with trees and soft ground. Noise should be dampened, with my tinywoop there is near to non sound after 5m.
So i will take a close look at the props maybe i can find some problems with those. Can there be a problem if they are not tightened enough ?

If not tight enough the motor will spin faster than it should and flight will be goofy as that motor won't give the correct response that it should. Yes, sound won't be right either.

(10-Oct-2021, 06:17 PM)MrSolo Wrote: A 5" freestyle quad is heard from a long distance away(few hundred meters). They are heavy, and require a lot of thrust to lift.

If you want quiet, I would recommend a lighter quad (250g or less), on 3" / 3.5" / 4" props.

The lighter the quad, the less air you need to move, the quieter it is. I have a 60g 3" Crux3 that is barely hearable past 10m. And a 140g digital 3" that is silent past about 50m or so. A 250g 3.5" is a bit louder than that. And a 630g 5" that is hearable from 200m.

exactly this but also weight related to rotorsize, where kaity named the rpms as indicater. multiblade rotors provide more thrust on lower rpms and are also quieter therefor.

a 250g 4inch is quieter than a 250g 3inch.
todays sub250g 4inch quads or 3inch 1s quads have a good ratio between uaw and rotorsize, all kinds of "ultralights" are pretty silent on cruising.

LOUD = agressively pushing air

Very light 2", 5" or even 8" will have faint hum just hovering.

But higher pitch = more annoying. And tiny micro needs to spin props much faster.

4 or 6 plade prop beats air more smoothly = "quieter"

My quietest.

120g 5" using rcinpower1506 and 2g 5030 props. Held together with plastic screws and rubber band.

Best practical quiet quad

4" using Xing1404 on 14g Picklefork frame. 81g dry.. people walking dogs in park didnt even notice it.

So it's easy: low disk load = low noise, for any prop size. High disk load will be noisy.

Big prop - low RPM, low pitch noise. Small prop - high pitch noise.

6 in quad, 560g AUW, with new Gemfan Flash 6042-2 props - quiet and I don't hear 100 m away.
4 in quad, 330g AUW, with Gemfan 4024-2 props - very efficient, but maybe twice as loud as the 6-in.

Moblite7 is probably something in between.

My 5” is by far the one that makes the most noise. If your looking for stealth a smaller or larger one would be better. With 7” 3 blade  makes a fraction of the noise of the 5” 3 blade both are 6s setups so kva is close. In my experience the biblades are also noisier.

I do love the loud aggressive noise that a 5" quad makes, and I still continue to get a kick out of doing a punch out 500 metres away followed by the 1 second speed of sound delay it takes before I then hear the resulting prop noise  But I fly out in the fields with no-one around to upset by me flying my 5" noise monsters.

Yes I particularly like the noise the 7” biblades produce. It’s loud and has an odd whirly sound to them that adds a creep factor in.

i like the deep sound of a nine inch or an xclass, but i dont own one xD i dont like their flightperformance enogh to get one, just about sound
as bigger the blade as deeper the sound, the tiny ones are screamers. my experience is that peoples around gets most annoyed by small powerfull quads like a 1408 on 3inch.

(12-Oct-2021, 09:48 AM)SnowLeopardFPV Wrote: I do love the loud aggressive noise that a 5" quad makes, and I still continue to get a kick out of doing a punch out 500 metres away followed by the 1 second speed of sound delay it takes before I then hear the resulting prop noise  But I fly out in the fields with no-one around to upset by me flying my 5" noise monsters.

Yeah that really messed with my head one time flying at a school about that distance from the quad and went to do a small powerloop on the covered walkway. I was all the way around before the sound hit me and on top of it was the delayed echo. Add that to the things the sim doesn't replicate that audible feedback and how it wildly varies when in the real world. 

People in the not so distant vicinity are wondering what the hell that child keeps screaming about.

So.. what have we learned?
3" thats 50g = quiet
3" thats 250g = noisy squelling mosquito