Phil: This is just a thought and can be a "Black Art" kind of thing. Have you ever considered the fact that a simple change of exhaust stack length could fix the problem. Sometimes the noise can be positively reinforced if your pipes length are close to multiples of the natural resonating frequency of the the engine and a change of length away drom the engines natural wave length may dampen it. Contact someone that understands harmonics and maybe take some readings with a frequency meter if you can find one.
Pick my brain from recollections out of Physics class. maybe something to look at but don't try it with out checking out the therory with someone that really knows acoustics. Remember the "Muscle Cars" of the 60's that had Tuned exhaust sytems to enhance performance. Don ------------------------------------------------------------------------ Frank Ross wrote: > Phil, > There are a lot of issues with noise sources that can complicate your > solution. Secondary vibration from the fuselage plywood and the plexiglass > canopy and even the fiberglass turtle-deck can combine to make considerable > noise. While you might not be able to address many of the causes, the use of > soft, noise-cancelling foam covered with light-weight cloth might help a lot. > Using the stiffer foams covered with thicker upholstery-type material might > look prettier, but is less effective when it comes to deadening the sound > that vibration causes in the cockpit. Also, you are faced with the problem of > not adding too much weight or anything that might come loose and get tangled > in the controls. > A lot of folk just think the noise is all part of the fun of flying. > Good luck, > Frank > > phil brookman <p...@ntlworld.com> wrote: > has anyone done anything to limit cockpit noise > my kr is realy quiet to peopole on the outside but in there i need it > quieter > at the moment i am thinking insultaion on the firewall > its only yhe lower notes that seem to get through - > my exhausts route under the plane > phil > > Frank Ross, > EAA Chapter 35, > San Geronimo, TX > RAF Lakenheath, Suffolk, England, UK > Visit my photo album at: > http://photos.yahoo.com/alamokr2 > > --------------------------------- > Blab-away for as little as 1ยข/min. Make PC-to-Phone Calls using Yahoo! > Messenger with Voice. > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > please see other KRnet info at http://www.krnet.org/info.html
