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Drone noise - what to do?
2430 16 2018-5-7
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Bekaru MP UAV
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Hi all,

Drones make a terrible sound.  
Not only is the noise too loud but it is also a horrible and fear invoking noise that sounds most like a swarm of bees or hornets which makes people fearful.

DJI obviously recognises that the prop noise is an issue, hense the 'quiet' new props.
Great idea - but do they work - what works about them - what is uncertain - why even bother - is there a way to  improve?

Why bother? because the noise that drones make annoys people and or frightens/scares people and this is a PR problem for DJI and DJI pilots.
Every one would benefit from less noisy drones.

What is uncertain? i have watched many videos of DB measurements of the differance between the two style props. The best improvement reading is saw showed about 5% db improvement - most though showed very little / negligable improvement.

What works about them? it seems to me that the noticable differance lies in the tone of sound the improved props make.

I believe that the sound improvement comes with a 'better tone' rather than an improved /lower db value. .

Is there a way to improve? I believe that first off the noise 'scares' people because of inherent human fears about swarms of bees or hornets - i think that is the part of the noise problem that DJI could mostly likely and most easily be able to do something about.
Already DJI has changed the pitch/ tone of the prop sound and universally that is something everyone seems to agree upon 'that it sounds better'.
Shortened Mavic pro Props.GIF
Why does it sound better? It is not that much quieter but it sounds a lot less like angry bees - thats why it sounds better.

As a personal experiment i cut 25% of the tips of my props and compared my drone sound to my mate (also with a mavic pro).
We did not use instruments, only our ears.
We agreed that the sound volume appeared about the same.
We agreed also that the shorter blades have a different tone (a slightly higher pitch).
We also agreed that the sound produced by the short props sounded better or at least less offensive or less scary.

I would request that DJI continue their pursuit to produce more pleasant sounding drone noise.
This would be great for Dji and awesome for dji pilots.


In closing i will add that i flew 2 batteries with my shortened an damaged props and i liked it.
My drone felt nippier, or slightly more quicker/sharper on response to stick comands.
Stability was great. Video footage did not show and issues.
I flew it around low level in sport at full stick - no problems - handled perfectly.
Me and my friend raced our mavics 200m up and down the park (he has the same mavic pro) - again it was not accurately measured (ready steady go) but after a few runs we had the feeeling that my speed performance was about the same as his.
My sport mode decent was quicker and smoother than with normal props.
I got about 3min less flight time per battery.


2018-5-7
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hallmark007
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Not to sure if the noise would be the biggest fear of drones, my neighbour cuts his grass twice a week in the summer his ride on is old and makes quite a bit of noise constant for about an hour, my drones take off from the back of my House noisy yes but only when landing and taking off, so neighbors don’t mind, if I fly around my neighbors for 1 hour then sure they would be more worried about the privacy issue but 1 hour well that’s taking the pi#s, and if anyone continually flys drones encroaching on others peace for long periods then, I call this ignorance.

These drones are not for the purpose of flying around people constantly they are annoying if your going to try do this, likewise taking it to the park on a Sunday ruining people’s afternoon is not on , it just takes a bit of Savvy to not be intrusive with these drones, yes if they can make them a little quieter fine, but don’t go annoying people just because you have the right to fly, have a bit of respect for others who will in turn respect your hobby.

Fly safe with respect for others.
2018-5-7
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forbsie
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hallmark007 Posted at 2018-5-7 16:13
Not to sure if the noise would be the biggest fear of drones, my neighbour cuts his grass twice a week in the summer his ride on is old and makes quite a bit of noise constant for about an hour, my drones take off from the back of my House noisy yes but only when landing and taking off, so neighbors don’t mind, if I fly around my neighbors for 1 hour then sure they would be more worried about the privacy issue but 1 hour well that’s taking the pi#s, and if anyone continually flys drones encroaching on others peace for long periods then, I call this ignorance.

These drones are not for the purpose of flying around people constantly they are annoying if your going to try do this, likewise taking it to the park on a Sunday ruining people’s afternoon is not on , it just takes a bit of Savvy to not be intrusive with these drones, yes if they can make them a little quieter fine, but don’t go annoying people just because you have the right to fly, have a bit of respect for others who will in turn respect your hobby.

Agreed! Whilst both my drones make quite a bit of noise on takeoff/landing, once they are in the air (and not all that high) the noise level almost disappears. Further, in my experience, the general populace are becoming more aware of drones and have shown an interest rather than fear of them.
2018-5-7
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DJI Diana
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hallmark007 Posted at 2018-5-7 16:13
Not to sure if the noise would be the biggest fear of drones, my neighbour cuts his grass twice a week in the summer his ride on is old and makes quite a bit of noise constant for about an hour, my drones take off from the back of my House noisy yes but only when landing and taking off, so neighbors don’t mind, if I fly around my neighbors for 1 hour then sure they would be more worried about the privacy issue but 1 hour well that’s taking the pi#s, and if anyone continually flys drones encroaching on others peace for long periods then, I call this ignorance.

These drones are not for the purpose of flying around people constantly they are annoying if your going to try do this, likewise taking it to the park on a Sunday ruining people’s afternoon is not on , it just takes a bit of Savvy to not be intrusive with these drones, yes if they can make them a little quieter fine, but don’t go annoying people just because you have the right to fly, have a bit of respect for others who will in turn respect your hobby.

Yes, agree with your opinion.
2018-5-7
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Bekaru MP UAV
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hallmark007 Posted at 2018-5-7 16:13
Not to sure if the noise would be the biggest fear of drones, my neighbour cuts his grass twice a week in the summer his ride on is old and makes quite a bit of noise constant for about an hour, my drones take off from the back of my House noisy yes but only when landing and taking off, so neighbors don’t mind, if I fly around my neighbors for 1 hour then sure they would be more worried about the privacy issue but 1 hour well that’s taking the pi#s, and if anyone continually flys drones encroaching on others peace for long periods then, I call this ignorance.

These drones are not for the purpose of flying around people constantly they are annoying if your going to try do this, likewise taking it to the park on a Sunday ruining people’s afternoon is not on , it just takes a bit of Savvy to not be intrusive with these drones, yes if they can make them a little quieter fine, but don’t go annoying people just because you have the right to fly, have a bit of respect for others who will in turn respect your hobby.

i agree with your views in your post entirely.

My post was an attempt to raise a particular point of interest which i am apparently not getting across well enough to be understood correctly.

My interest in improved props is not so much for the volume of the noise but for the pitch of the tone or the sound it makes.
My suggestion does not go to how to make the noise quieter - (as far as i am concerned the noise level can remain the same) the idea i am trying to introduce is that if the noise tone could be altered to sound less like a sound that invokes fear (not because it is a drone noise but because it is a sound that is associated with swarming bees or hornets which invokes fear in people).

I understand what you say about not flying close to people so the noise can be heard - the drone can still be heard 100m over my head but the aspect of being too close to people is not relevant to why i introduced this post.

By designing and producing new 'quieter props' is an obvious acknowledgement by dji that such an improvement is desirable.
i am simply adding my voice to that desire and taking it a step further by making suggestions as to what aspect of that noise is so offensive.
I am trying to bring about the point that the props are apparently not that much quieter but people still like them because of something - it seems they like it because the tone is different.
I am thinking what is it about the new tone that people prefer - then i thought what is it about the old tone that makes people prefer the new tone better.
Then i realised that it is because of what the original tone sounds like - it sounds like swarming bees and the new sound does not.
So i thought - well this seems to be really the area where improvement was made and so by my post i am adding my views on the subject.
2018-5-8
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Bekaru MP UAV
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forbsie Posted at 2018-5-7 16:54
Agreed! Whilst both my drones make quite a bit of noise on takeoff/landing, once they are in the air (and not all that high) the noise level almost disappears. Further, in my experience, the general populace are becoming more aware of drones and have shown an interest rather than fear of them.

in my year of flying i have had many encounters with general public. I feel confident to say at 50 but probably closer to 100 maybe even more.

In total i have a 1 negative encounter.

My post is about 'what aspect of the drone sound' could be improved and what makes me think so.

i am not making a point for quieter props - i am making a point for less angry sounding tone.
I can easily hear my mavic pro 100m up - maybe the other mavics are quieter or maybe you do not hear them so much because their pitch (the sound they make) is not the same as the mavic sound.
Dji has conceptualized and produced quieter props so my idea is in line with their idealism - and if my post is read and understood correctly then i think it offers an interesting contribution.

2018-5-8
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Bekaru MP UAV
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DJI Diana Posted at 2018-5-7 19:31
Yes, agree with your opinion.

please feel free to review posts 5 and 6.

I also agree with the other posts opinion - however they miss the point of the post and are therefore irrelevant in respect of this post.

This post is about something that dji itself is keenly interested in - therefore they conceptualised and produced 'quieter' props.
My post concentrates only on this 'quieter' aspect and what it is about this new sound that i think dji has achieved.

Dji sells the new props as 'quieter' - my post simply tries to explore this concept.
Is the prop actually quieter or is it really just the sound that is different. It seems to be the latter.

The misconception i am exploring in my post is the difference between quieter and different sound.
Dji is in pursuit of quieter props - this is obvious.

My post tries to introduce the idea that rather than worrying about trying to improve the volume to be less, i think a possible way to a sound improvement would be to continue if possible to adjust the tone of the out put sound.
This has already been achieved in the new props - my suggestion is that by playing more with this design aspect perhaps more improvements to final sound out put can be achieved.

This is simply an idea which i think either dji already knows about or if they do'nt that someone in the propeller development team might be interested to think about.

It is MP drone related and inline with dji direction of progress.

I think that if my post is understood correctly that it raises and interesting idea.
Perhaps dji is already onto this.
Perhaps it is not a good idea?

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forbsie
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Bekaru MP UAV Posted at 2018-5-8 01:04
in my year of flying i have had many encounters with general public. I feel confident to say at 50 but probably closer to 100 maybe even more.

In total i have a 1 negative encounter.

I absolutely agree that any improvement in propellor noise would be a worthwhile enhancement. Have you tried the new Mavic Pro Platinum propellors? They are available as a separate purchase and are apparently a lot quieter.  
2018-5-8
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Bekaru MP UAV
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forbsie Posted at 2018-5-8 01:51
I absolutely agree that any improvement in propellor noise would be a worthwhile enhancement. Have you tried the new Mavic Pro Platinum propellors? They are available as a separate purchase and are apparently a lot quieter.

a friend is going to USA next month and will bring me back a set but i watched many you tube videos about tests between the two.

I will get them because the sound they make is nicer.
It is not that i think it is a nice sound just that i think it is a less offensive sound (harmonics wise) than the original props.

From one generation prop design to the next dji successfully made a sound (harmonics) improvement.
They sell them as quieter props so i think they are thinking that the props are quieter (when in fact they are not) so how can we improve on that quietness (which they did not) - so they are looking in the wrong direction.
What they did improve on is the tonal sound. If they recognise that this is in fact the area of improvement and perhaps worked on that aspect some more (rather than focusing on the db loudness value) - then perhaps more improvements could be made.
It may still be as loud but it may sound nicer or less 'angry' (in a harmonics sense)



2018-5-8
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R&L Aerial photography
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Lower kv motors with props of greater pitch produce much less noise but that’s not the route DJI chose hopefully the will offer low nois models in the future...
2018-5-8
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Bob Brown
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hallmark007 Posted at 2018-5-7 16:13
Not to sure if the noise would be the biggest fear of drones, my neighbour cuts his grass twice a week in the summer his ride on is old and makes quite a bit of noise constant for about an hour, my drones take off from the back of my House noisy yes but only when landing and taking off, so neighbors don’t mind, if I fly around my neighbors for 1 hour then sure they would be more worried about the privacy issue but 1 hour well that’s taking the pi#s, and if anyone continually flys drones encroaching on others peace for long periods then, I call this ignorance.

These drones are not for the purpose of flying around people constantly they are annoying if your going to try do this, likewise taking it to the park on a Sunday ruining people’s afternoon is not on , it just takes a bit of Savvy to not be intrusive with these drones, yes if they can make them a little quieter fine, but don’t go annoying people just because you have the right to fly, have a bit of respect for others who will in turn respect your hobby.

I fly the neighborhood quite often... I use a neighborhood facebook page to communicate my intentions and also post pics and videos there of flights. Seems to get good feedback and allows people to communicate directly with any concerns. The sound of the drone is what makes it more awesome and "alerts" people to it's presence. Without the sound people may think of it more as a spy machine/too stealthy. A swarm of bees... probably does not insite fear in my area since that never happens. People here are not conditioned to fear bees or swarms. Just not a concern.
2018-5-8
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Landbo
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Bekaru MP UAV Posted at 2018-5-8 02:36
a friend is going to USA next month and will bring me back a set but i watched many you tube videos about tests between the two.

I will get them because the sound they make is nicer.

The new low noise props reduce the noise by lowering the engine's RPM. Furthermore, the new design also has a certain ability to lower the noise. In my experience, they work really well.

And yes, DJI should work hard to reduce noise from props.

Regards Leif.
2018-5-8
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Lamplighter55
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Its a pitch thing - DJI have created the 'lower noise' props so that the sound/frequency envelop has a reduced amplitude around the mid-tone range that the majority of human ears are a-tuned to. In theory you'd have to lower the rev and broaden the surface area of the props to reduce the prop wash sound further. Some folk are less sensitive to high frequency sounds so find it hard to tell the difference.
2018-5-8
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Bekaru MP UAV
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Lamplighter55 Posted at 2018-5-8 05:01
Its a pitch thing - DJI have created the 'lower noise' props so that the sound/frequency envelop has a reduced amplitude around the mid-tone range that the majority of human ears are a-tuned to. In theory you'd have to lower the rev and broaden the surface area of the props to reduce the prop wash sound further. Some folk are less sensitive to high frequency sounds so find it hard to tell the difference.

thanks for an interesting contribution. yep - it really does seem to be a pitch thing.

I wonder how a double prop system will influence the sound.
Theoretically the revs could be reduced so that could help on that aspect of the sound - would be interesting to know how that could sound.
These are just curious thoughts and thinking out aloud on the forum.


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Bulldog
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Even with the best tech, our best military choppers make noise. It's the nature of the beast, until anti gravity technology takes over.
2018-5-8
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Mangofly
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Interesting video how you can reduce the wing noise. Could it be applicable on our blades?

2018-5-8
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Bekaru MP UAV
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Mangofly Posted at 2018-5-8 12:45
Interesting video how you can reduce the wing noise. Could it be applicable on our blades?

https://youtu.be/1qZnB6Ifueo

thanks magofly - i turned my volume right up but still heard no sound from the video - must work very well:-)
Anyway looks like an interesting way they set about reducing the sound by making serrated edges.
I will see if there is some way i can give it a try.
2018-5-8
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