We have a 91 dB limit for one of our courses. My Flowmaster is pretty loud, so I thought I'd better do something to be a good citizen.

I have round tailpipes. I got 2 stainless steel sink strainers, and with washers bolted them to a threaded rod. I made one of these for each tail pipe, slipped them in, and held them there with piece of coathanger wire going through a couple holes I drilled.

Not sure how much lower a decibel meter would read, but sure sounds alot quieter.

One last caveat: The first sink strainer I used was flimsy and bent from the exhaust. My new ones are much stronger and are holding up great (plus they are easy to remove). They rattle a bit, so I still need to shim them in tighter somehow, maybe wrap some wire around the perimeter.