Hi all

Plenty of videos on YouTube comparing the new props, but none seemed to be carried out in a controlled manner that accurately compared the same flight conditions whilst accurately measuring sound levels.
So I cleared the studio and did 2 identical flights to compare side-by-side, then another two flights outside.  
I'm left wondering if these really make a genuine difference....

Cheers,
Ian

  

By that they don’t seem worth worrying about

Thanks Ian, good demo!

Was flying the new props yesterday, didn’t notice any difference at all. Guess I was taken in by the hype.

Don't know why, but I think it makes a world of difference. I live out in the middle of nowhere, and the ambient noise is really low. For me, it was night and day. The pitch was softer, and the sound was less. Clear difference for me, but I don't have equipment to quantify, Thanks for making the video.

The pitch (frequency) of the new props is supposedly lower than the originals.  The plethora of videos of people pointing a camera at a sound meter (just like the many that came before this one) don't really take that into account.

Say you had two musical instruments both playing the same volume as measured by a sound meter.  The tenor saxophone has a mellow meaty sound, whereas the clarinet sounds like a canary getting its head twisted off.  You'd say the clarinet is louder even though it's not.

That may explain why many claim there's a difference even though it hasn't really shown up in numbers.  Also keep in mind that not all people's ears react the same across the frequency spectrum, especially given age differences.

Next up...side by side MP vs MPP. ready Go.

Thanks for this!

Flew with mine this morning, same observation slight pitch difference (which I prefer) but not much quieter. Thanks for sharing

Irate Retro Posted at 2017-10-21 05:05
The pitch (frequency) of the new props is supposedly lower than the originals.  The plethora of videos of people pointing a camera at a sound meter (just like the many that came before this one) don't really take that into account.

Say you had two musical instruments both playing the same volume as measured by a sound meter.  The tenor saxophone has a mellow meaty sound, whereas the clarinet sounds like a canary getting its head twisted off.  You'd say the clarinet is louder even though it's not.

This is true.  That's why I edited the video to flip between the sound of the new and old repeatedly.  The pitch is indeed key here, as the actual reduction in perceived sound is due to a reduction in upper mid-range frequencies that so often 'annoy' us.  
Some people that are more sensitive to these frequency ranges will indeed perceive them to be quieter.  So yes, could be argued I was being a bit too focused on the overall dB level without taking the finer frequency analysis into consideration.
Cheers,

Ian

http://www.youtube.com/IaninLondon

I recently equipped my Mavic with those propellers, and Subjectevley they are much quieter than original ones. I have sound meter but did not bother to use it as I had flights to do
Thanks for Your review.

Good review and far more of a sensible test than most of the other youtube videos.  Its fit into the official explanation of frequency and harmonics being different whereas actual sound levels aren't.
On a new drone with new ESCs the new props have a modest effect.  It stands to reason the same props on older generation ESCs wont be as effective and your tests seem to back this up nicely.
Nearly all the other tests done are just "i think therefore it is" and a perfect example of placebo effect and confirmation bias.

Obvious a properly controlled, repeated series of blind tests would be great but thats hard to do without a lot more organisation.

GrahamG Posted at 2017-10-21 04:31
Was flying the new props yesterday, didn’t notice any difference at all. Guess I was taken in by the hype.

Yup same here, I think DJI succeeded in their promotional campaign, create the hype buy introducing a "Quieter" prop, put out FW update to compensate adding new props to old Mavic, everyone gets caught up in it (like me) and the end result, hundreds of thousands of props sold at an inflated price and no one with a little wax in their ears will be able to tell the difference. Brilliant marketing !!!

DJI not once promoted reduced noise on a standard mavic.  That was just people on the internet reading it and guessing.
DJIs *ONLY* claim was the props change the frequency response and up to a max 4db noise reduction on the new mavic platinum with the upgraded ESCs.
Their only claim for the mavic pro was the props will work on it, which they do.  They've made no noise claims what-so-ever.

The entire "MUST HAVE PLATINUM PROPS" fad was created by users on the internet desperate for the newest shiny shiny (and after buying, most convince themselves it makes a difference.  Confirmation bias in action).

GrahamG Posted at 2017-10-21 04:31
Was flying the new props yesterday, didn’t notice any difference at all. Guess I was taken in by the hype.

As Wellsi and several other pointed out, the lower pitch is the key here. Even at the same amplitude, the lower pitch in the upper-mid range will be perceived and "quieter" or "more pleasing".

I am still waiting for my set to arrive, but from what I've seen of the various side-by-side comparisons, the new ones are drawing less audible attention to them.

EDIT: A review in the following thread dives into the distinction between pitch and amplitude:
https://forum.dji.com/thread-116837-1-3.html

gnirtS Posted at 2017-10-22 03:22
DJI not once promoted reduced noise on a standard mavic.  That was just people on the internet reading it and guessing.
DJIs *ONLY* claim was the props change the frequency response and up to a max 4db noise reduction on the new mavic platinum with the upgraded ESCs.
Their only claim for the mavic pro was the props will work on it, which they do.  They've made no noise claims what-so-ever.

I definitely remember the latest update to include the ESC calibration to facilitate the new props being installed on the Mavic Pro. Yes I agree no direct promotion, but I'm pretty sure they knew the frenzy it would cause. The Chinese didn't get to the top of the economic ladder buy not being market savvy.

https://forum.dji.com/thread-113562-1-1.html

Its not DJIs fault people are stupid though.  They havent made any claims.  The clueless fan base did without understanding anything about the technology or physics.
The props work on the standard mavic and there maybe a slightly, laboratory measurable decrease in sound output compared to the other props.  Thats about it.  Real world difference likely to be none.

Again i'd like to see someone to a proper blind test with non-drone users (so they dont associate any potentially different sound with different props) to see if there is any practical difference at all in the real world.

Pitch, amplitude, dB all very impressive. I went thru 4 batteries and I picked up the sound of my returning mavic at roughly the same distance as with the old props. All I would say is ..if you want to buy these new props for a quieter flight, don’t bother.

gnirtS Posted at 2017-10-22 03:22
DJI not once promoted reduced noise on a standard mavic.  That was just people on the internet reading it and guessing.
DJIs *ONLY* claim was the props change the frequency response and up to a max 4db noise reduction on the new mavic platinum with the upgraded ESCs.
Their only claim for the mavic pro was the props will work on it, which they do.  They've made no noise claims what-so-ever.

Not quite....
DJI do make the lower noise claim on the Propellers' web page and specifically mention the noise reduction will also apply to the standard Mavic:

https://store.dji.com/product/mavic-low-noise-quick-release-props-platinum

"Noise reduction and flight time are also enhanced when used with the Mavic Pro, but not as much."

Wellsi Posted at 2017-10-22 04:57
Not quite....
DJI do make the lower noise claim on the Propellers' web page and specifically mention the noise reduction will also apply to the standard Mavic:

Lower pitch propellers sound quieter when they become louder.
This is a paradoxical effect.

From the Dept. of Physic and Anatomy, Georgia State University

Effect of Loudness Changes on Perceived Pitch

A high pitch (>2kHz) will be perceived to be getting higher if its loudness is increased, whereas a low pitch (<2kHz) will be perceived to be going lower with increased loudness. Sometimes called "Stevens's rule" after an early investigator, this psychoacoustic effect has been extensively investigated.

With an increase of sound intensity from 60 to 90 decibels, Terhardt found that the pitch of a 6kHz pure tone was perceived to rise over 30 cents. A 200 Hz tone was found to drop about 20 cents in perceived pitch over the same intensity change.

Studies with the sounds of musical instruments show less perceived pitch change with increasing intensity. Rossing reports a perceived pitch change of around 17 cents for a change from 65 dB to 95 dB. This perceived change can be upward or downward, depending upon which harmonics are predominant. For example, if the majority of the intensity comes from harmonics which are above 2 kHz, the perceived pitch shift will be upward.
http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html

Wellsi Posted at 2017-10-22 04:57
Not quite....
DJI do make the lower noise claim on the Propellers' web page and specifically mention the noise reduction will also apply to the standard Mavic:

Which is 100% accurate.  People are measuring 1-2db.  They've been 100% honest with these things.  Internet hype did the rest.  People always want shiny shiny and convince themselves its amazing then tryo to convince others the same.

thanks ian - good review, appreciate it.

I love the new propellers. The 3-4 db difference is not that much but the new propellers are less annoying than the original ones. The original ones had this high pitch lawn mower noise to it. The new ones had a lower pitch sound to it and is less annoying.

My opinion, way better than the originals, the high pitch has gone and the drone seems more Relaxed overall.

Have to say, when I was out flying over a forest the other day, I could still hear the high pitched buzzing same as usual...  I really do think you only notice the difference when you do a side-by-side comparison... Once they're fitted and you're flying, it's pretty much the same old buzz in my opinion.  But as people have mentioned, different people have different sensitivities to different frequencies....

Cheers,
Ian

Mate, your level of dedication is amazing!  However, THAT is the furthest thing from an acoustically correct studio & measuring equipment.  I still really enjoy your videos.  

Irate Retro Posted at 2017-10-21 05:05
The pitch (frequency) of the new props is supposedly lower than the originals.  The plethora of videos of people pointing a camera at a sound meter (just like the many that came before this one) don't really take that into account.

Say you had two musical instruments both playing the same volume as measured by a sound meter.  The tenor saxophone has a mellow meaty sound, whereas the clarinet sounds like a canary getting its head twisted off.  You'd say the clarinet is louder even though it's not.

Exactly, what would be meaningful is what a spectrum analyzer hears for each prop type.

DRONE-flies-YOU Posted at 2017-10-25 22:22
Mate, your level of dedication is amazing!  However, THAT is the furthest thing from an acoustically correct studio & measuring equipment.  I still really enjoy your videos.

lol... Yes, it's a photography studio, not an acoustic studio.  But it did allow me to record 2 identical flights with no exterior factors like wind, at precisely the same height and distance from a sound meter....  And confirmed to me what my ears were already telling me... Lower pitch but just as loud....
Glad you like the vids; they're all for fun!  
Cheers
Ian

https://www.youtube.com/IaninLondon

I just received my set of blades today and did an idle-run comparison. Started Mavic's engines. Let them run idle without taking off. Pushed the left stick left, then idle, then right. Then pushed right stick left - idle - right - idle - up - down.
Mavic would apply differential to the engine output in the idle mode, so it's possible to hear how the old and the new blades performed in these modes.

Overall - the amplitude (loudness) was the same, but the pitch was different, lower on the new ones. Noting the RPM readings, the new blades resulted in 10-15 lower RPM (readings x10):

Idle old: 190
Idle new: 175

Yaw left old: 219
Yaw left new: 207

Yaw right old: 219
Yaw left new: 207

Bank left old: 195
Bank left new: 180

Bank right old: 195
Bank right new: 180

Pitch forward old: 200
Pitch forward new: 189

Pitch backward old: 180
Pitch backward new: 165

Backward differential resulted by far the quietest operation.

If weather allows, will be taking the bird for a flight this week-end.

Wish my Mavic had the wings of an Owl !! This is the test to really see what's happening with the 8331's