I have 6" miter cuts on my dually and it is pretty loud with the windows down, and especially with the back window open. With the windows up though its not too ridiculous. Put a muffler on it, stack it and never look back. I'll never be without stacks again. H*ll, I put stacks on my smoker/grill and my go-kart. HEHE, they're good.
-R. J.