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Exhaust silencer

edmondthx1138

edmondthx1138

Member
Does anyone have experience or an opinion on modifying the muffler or exhaust pipe to reduce noise? My research indicates that a large amount of engine noise comes from the hot cases escaping and causing pulse waves.

The simplest solution I can think of is expanding the diameter of the exhaust pipe, and/or its length, and/or adding some kind of silencer baffles.

Any thoughts?
 
An RV-12 from the “outside” sounds like a sewing machine. If you want to tame cabin noise... the best solution is ANR headset. I have LightSpeed Zulu3 and 912ULS sounds like a small turbine running at partial power…
 
The ANR does a better job with the lower pitched Lycomings/Conts than Rotax.. wish they'd come out with a headset specific for the Rotaxes of the world.. I'd go with existing ANR above any other noise suppression method tho.
 
You can put a muffler on your plane. there is not a lot of room under the cowl so there is a design called a "swiss muffler". It is basically a glass pack your exhaust dumps into. It adds weight and drag but it will be more quite. We are running OPEN headers, so it is loud.

If you are talking about noise in cockpit yes the power pulse is pounding the floor boards. There sound deadening mat. That reduces the drumming. However it is an AIR COOLED engine, no water jackets around the jugs. You hear the valves, piston slap, combustion in a concoctony of mechanical music. You have a piece of sheet metal between you and the engine. Again people put sound proofing there.

However noise is coming out of the cowl (fiberglass) and your plexi windscreen is not that sound proof. Many super luxury cars use thicker glass. All sound reduction is at cost of weight, cost and may be drag. As was said above that is why we have hearing protection. My first flight lesson used a hand help mic and overhead speaker... ha ha. I got portable intercom and headset very fast.
 
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Yes, I think ANR headsets, while a great innovation, are limited. I just tried foam ear plugs combined with both my Bose A20 and Lightspeed.

The surprising result was, if you insert the plugs as directed (yes, there is a procedure) removing the headset at various cruise speeds, I could not sense any difference in sound.

The plugs were sufficient on their own. So, a quick solution for (my) sensitive ears are to use foam ear plugs AND the ANR headset. The plugs protect my hearing, and the headset lets me communicate.
 
And yes, I agree that most pilots get better success with their ANR headsets given their Lycoming, etc. engines. The Rotax's higher RPMs produce different frequencies, etc.
 
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