When I got Valk, it had 2bros 6x6 pipes on it. One of the first things I did was buy molded earplugs and a pair of BE 1C molded earbuds from Big Ear.
http://www.bigearinc.com/Products/BE-1C.aspx I could still hear sirens and horns, but the pipes were muffled to the point I could tell the engine was running, but there was no headache after a ride. With the earbuds, it was the same story, except that instead of engine noise, it sounded like I was at the symphony. I no longer have the loud pipes, but the earplugs work great while mowing the yard.