Noise

greeny

Senior Member
Joined
Jul 20, 2004
Messages
178
Location
Mollis
Aircraft
Gyro DF-02 HB-YPS
Total Flight Time
600
Only a short time ago, our authorities made it possible to legally build and fly experimentals here. And gyrocopters are among the types of aircraft one might build. But up to this very moment, there is no one of them in the whole country. Trying to gather some information, I turn to the experts on this forum for help.
One of my questions is about noise: In certain threads, I found gyros referred to as "screamers". Which leads to the conclusion that they are far from quiet.
Obviously, when you use a two stroke, air cooled engine with high revs, this setup would produce more noise than a liquid cooled with reduction drive. And a four blade propeller is likely to be less noisy than a two blader.
Are there propellers which are less noisy than others?
Does the construction of the rotor influence the noise it makes?
Would a puller design be less noisy than a pusher?
Is it possible to quantify from what part how much noise is coming?

Thanks for sharing your wisdom.

Peter

www.berge.gl
 
Noise

Peter,
The more propeller blades you use, the more noise you create. The actual decibel level increases. The faster you turn your propeller no matter how many blades, the more noise you make. An autorotating rotor does not make much more sound than a gentle swish in flight until you "yank and bank" causing the rotor to momentarily speed up, pound the air, and then return to normal flight RPM. The efficiency of the rotor airfoil does have some effect of the level of rotor noise, but again this would be minimal. A tractor configuration will almost always be more quiet because the propeller is "seeing" clean air, you can generally turn a larger diameter propeller slower, and the engine exhaust will not be flowing through the propeller.
 
Peter, these is the quietest and best performing props I have experimented with for the production of my Firebird gyroplane.

Aussie Paul.
 

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Great performing and extremelly quiet props

Great performing and extremelly quiet props

I can use my hand held cell phone just like in a car. :cool:

Mike is the guy who makes these fine products. Mike is an aeronautical engineer by trade. He enjoys building props, and is always asked to design specialty historic props for rebuilds of WW1 planes. :D

Aussie Paul. :)
 

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Matt, AUD$ 1200 plus freight. Since the pics were taken we now have composite protection on the leading edge. I hope this helps.

Hqave a look on the Oz forum under props. www.asra.org.au
under the forum section. Geez I have to hit the sack!!!!

Aussie Paul.
 
Matt, Thats about $874.92 U.S at the current conversion rate.
 
Prince props are also quieter and go for about $900 U.S., I believe. At least that's what I paid for mine a few years ago. The local airport-rats thought I got some kind of new exhaust system when I switched from the Warp.
 
I have to say Ken that I found my prince quite ok, but the Oz timber prop is equal to if not a little better, and does not have that resonance problem that I was trying to work out with Lonnie when I smashed it.

Aussie Paul.
 
Paul, I only had a little resonance with the RAF tail. There is none with the Sparrowhawk tail.
 
Well Ken we need a head on head test then!!!!!!!! LOL

Aussie Paul.
 
How about someone getting a Radio Shack dB meter and getting some data other than "sounds a little quieter"? Come up with some kind of common criteria for comparison, like how loud is a machine at about 100 feet away when the gyro has just left the ground at takeoff.

It would be nice if someone at Mentone could get the data and compile it along with engine/prop combinations.
 
I expect to be at El Mirage with the same laptop I use for audio editing. It wouldn't be too tough to record some passes and measure them very precisely. I'll archive the audio files in digital form to allow any future analysis requiring re-weighting of the frequency response, etc.
 
Well,hell must have frozen over coz me and Paul B. agree on somthing. :D

I had an identical prop on my RAF[back when I had the ej22] and the difference in performance,efficiancy and sound was amasing.The volume was only a fraction of that of the Warp Drive,and the tone was much lower,[2 blades].Sounded more like a Cessna.

The 912 on my mustering machine has a streight through [no muffler]exhaust setup,and I still can't hear the engine noise over the warp drive. :mad:

I reckon with the high production typs of props,[3 or more blades and narrow chords]the prop produces 80% of flight noise ,if not more.
The wide chord Ivo Magnum[60"] on the 914 is much quieter than the narrow warp drive[68"] on the 912, both have 3 blades. :)
 
Birdy, you don't have the cockpit adjustable IVO prop, do you? I'd sure like to get some feedback on that thing.

Alright, who's the smart-ass? I'll have you know that cartoon is now B.S. I'm finishing up a 2 year program of Lamisil, and my nails are almost perfect. Want me to show proof?
 
Naw Ken,just a regular ground job..

Them toes! :eek: !Man,I thought mine were crook. :)

How do you put pix on the posts like that??

BTW,I reckon I sent you an E mail thingy last night,wunder'n if it worked??
 
Oops. I did get a message from you in my Hotmail account, but when I answered you it said it failed. Use kensandyeggo@(*****)san.rr.com. Take out the (*****), just in case some shmuck somewhere is harvesting e-mail addresses from the Forum.
 
Decibels and sound frequency!!!!!!!!!!!!!

Decibels and sound frequency!!!!!!!!!!!!!

Gary, the problem that manufacturers have is the sole reliance on db readings by the authorities. When I was still a Raf golden haired boy I approached Peter at Raf to explain that I thought we needed a redrive ratio greater than the 2.1. My figures showed at that time something like 2.4, to reduce the prop tip speed.

Peter told me that they had produced a 2.37, and would I be interested in trying it for evaluation purposes? I told him I would love to, so he sent it out. The 2.37 lowers the tip speed 12%. The staqndard Raf 3 blade 68" warp drive had to be 17 degrees to keep the engine rpm acceptable!!!!! I had a Raf supplied 68" WD 4 blade so I put that on at 14 degrees and wow!! that was pretty good.

Remember this was back in 1999 when I knew less that I know now.

I came back from flying dual and all the "airport rats" :D as ken J calls them came over to see what I had done to reduce the noise much.

Reporting back to Raf I told them the story. Don said that I was wrong, and that their db meter had said that there was no change in the readings and testing showed that the performance was less with the 2.37 with the 4 blade. I told Don that I did not notice any change in perfomance.

I spoke via email to the guy who did the flight testing when Raf did the measurements and he told me that Don was in a shitty :mad: mood with everyone that day!!!! He said that he did not really notice any performance difference except that maybe the acceleration when full power was applied on take off may have been slightly less.

I told Don that I felt sorry for the manufactures, :( becaus it is not only the dbs that are problem it is the frequency as well, and that the governing bodies should take into account the frequency of the sound as well as the dbs.

I would rather have the neighbourhod friendly sound :D and a slight decrease in take off performance, if it really was!!!!

You can have 2 sounds at the same db. One will make people unhappy and the other people won't notice.

The "airport rats" and people who live close to the flight path are the best guide for sound.

When I went to the Prince Ptip and then to the Oz prop it got better and better.

Well!!! that is a page of trivea. :eek:

Aussie Paul. :)
 
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