California Air Tools suggestions are good, a 1750rpm motor spinning around 700-800rpm pump will always be more quiet then those typical "5hp" big box store compressors.
Champion is a great choice, but Emax Compressors have been impressing me lately. Check them out- Silent Series, made in USA, lots of nice features:
Emax Silent 5hp 1ph 80 gallon - ESP05V080I1
Read more about air compressors in this review!