If you look up 'hofer gurglebuster' you'll come across another method of quieting your drain. I believe it's actually a variation of the Stockman. I don't have personal experience with either of these and did read that it may be more prone to clogging, but you may want to investigate nevertheless. Here's a link to get you started.
http://home.everestkc.net/jrobertson...struction.html