Noise, where does it come from?

Tom-D

Tom-D

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Tom-D
When you are close to the aircraft, and it is turning at full power, how much of the noise is the prop and how much is the engine?
 
I feel like turbo prop engines are loud as heck and the noise is mostly the whine of the engine.

I believe in most cases the engine is what makes up most of the noise.
Planes don't seem to have the noise reduction (mufflers) that cars do as far as I can tell.
I am only speculating though.
 
Depends on the plane.

Garretts are quite loud if your infront of them, quiet if you're not.

If your prop goes supersonic that'll make some noise.

All depends IMO.
 
Most of the noise comes from the prop. At least that is what I have always been told. I guess one way to look at it and this is pure anecdotal type of evidence is to consider a VW engine that is in a VW car versus one that has been put into a homebuilt aircraft with a prop. What is the difference in noise level of the two? Relevant? You tell me.
 
Many airplanes allow changing throttle and prop independently. Prop noise will depend only on RPM.

It seems to matter quite a lot with small reductions in RPM from top of the green in the 177 and 182, which suggests it's mostly prop noise up there. Probably much less so at lower RPM.

Some airplanes DO have mufflers. It's mentioned in the 172 and 182 POHs at least.

Comparing to a car doesn't work due to the very different exhaust system.
 
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There is a computer program that analyses aircraft sound and provides RPM (a tachometer). In the set up, it asks how many blades the prop has, not how many cylinders the engine has.

That doesn't answer your question but it might provide an indication.
 
SkyDog58 said:
Most of the noise comes from the prop. At least that is what I have always been told. I guess one way to look at it and this is pure anecdotal type of evidence is to consider a VW engine that is in a VW car versus one that has been put into a homebuilt aircraft with a prop. What is the difference in noise level of the two? Relevant? You tell me.
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VWs in cars have mufflers, VWs in airplanes generally don't.

I was flying formation with another Fly Baby once, when the plane banked away. Even with ear plugs in, I could hear the engine noise for just a moment as his A65's exhaust pipe pointed in my direction. So my vote is that it's that what we hear is mostly engine noise. Of course, if you let the prop tips go supersonic....

Ron Wanttaja
 
Three blade prop was noticeably quieter than the two blades when changed out on same aircraft. Maybe revalant to topic?
 
Skip Miller said:
And PA-28's and -32's. -Skip
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Yep...just got mine reworked from Dawley and reinstalled yesterday. They are more like glass packs though.

That's funny this came up because I had a buddy just yesterday ask if my plane will be quieter now that the mufflers are fixed. I told him nope as I beleive most of the noise is prop noise.
 
I have a muffler on my O-320... but it's just not a terribly effective muffler!
 
Greenhead said:
Three blade prop was noticeably quieter than the two blades when changed out on same aircraft. Maybe revalant to topic?
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For sure!

I get away with my three blade, but even living in the country, if I did a early morning take off with a 88" 2 blade, I think I'd get a few phone calls lol
 
Tom-D said:
When you are close to the aircraft, and it is turning at full power, how much of the noise is the prop and how much is the engine?
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Mostly the prop, because the tips are moving much faster than anything going up, down, or around in the guts of the engine.
 
Most GA planes, I'd say the prop all the time. With an airliner, I'd say the turbines on takeoff and the airframe on landing.
 
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