Mark Steitle wrote:

Mike,
 My first line of defense against the noise is an ANR headset.  That's a given.
 I purchased some black foam from ACS that I installed on the interior walls and floor.  From what I've read a lot of the noise comes in through the firewall and windows.  Not much you can do about the windows, but it seems that a generous amount of soundproofing on the firewall will help the most. Lastly, you can turn the exhaust down so that it is directed away from the occupants?  Or, run it back behind the pax, and fly faster than the speed of sound so it can't catch up to you. Mark S.

On Sat, Sep 12, 2009 at 10:15 AM, Mike Wills <rv-4mike@cox.net <mailto:rv-4mike@cox.net>> wrote:

    I asked a few days ago and got no replies. Since things are a bit
    slow on the list now I'll try again. Anyone have any
    recommendations for a decent soundproofing material that I can add
    to my firewall and floorboards to tame this racket? Maybe the rest
    of the world will have to deal with the noise, but at least I can
    try to make it a little more pleasant for me.
     Mike Wills
    RV-4 N144MW

Running it back past the occupants can actually be effective. Turning it down adds drag.

I've often wondered why no one has tried carrying the pipes down several inches below the fuselage before turning them aft, and installing streamline inserts aft of the downpipes & between the fuselage bottom & the horizontal run of pipe, to get smooth air between the fuselage & the now-parallel exhaust stream.

Charlie

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