Okay so i recently bought a 1u server on ebay... its a P3, 866MHz etc etc.
anyway, its noisy as hell. i've been thinking about putting some of my left over sound deadener the inside of the case to stop some of the noise.. its flippin loud. think it'll work?
Your best bet would be to replace the fans with quieter versions of the same size. That's where the majority of your noise is coming from in a rack-mount server. Especially considering the fans used in the power supplies.
You can use a thin deadener, but I doubt it will make a large difference.