Better muffler for small engine?

[Sherwood Botsford]

I have a 9 hp subaru engine that operates a soil mixer. I find it obnoxiously loud. From other reading the 'mufflers' on many small engines are little more than spark arresters. The location of the engine (about 6 feet off the ground, and the exhaust (on top) make me think that it should be possible to direct most of the sound energy upward with an appropriate bell.

Suggestions as to the actual structure appreciated. Do I want massive? light weight? exponential curve vs stepped?

 

[Baluncore]

How many cylinders ?
2 or 4 stroke ?
Does it run at a fixed RPM ?

 

[Sherwood Botsford]

1 cylinder (who makes a multi-cylinder 9 hp utility engine?)
4 stroke.
Constant RPM

Think big lawnmower engine.

 

[Nidum]

Chimney stack silencer - use pipe a bit bigger than one fitted to engine and arrange outlet well above your working level .

Similar but go horizontally and have the outlet some distance away from you and ideally behind a hedge or a wall .

Feed engine exhaust into a large oil drum or similar fitted with alternate baffles .

Always allow for very generous free flow area in exhaust system extensions . Make provision for condensation to drain away when engine is not in use .

 

[Nidum]

I once came across a saw mill engine where the normal engine exhaust was being fed into a large and very rusty truck silencer with the exit end poking out through the equally rusty shed roof .

This set up worked well and there was very little exhaust noise to be heard .