Compared to an open exhaust, it's more quiet. lol. I can't think of any way to really answer your question properly. There are lots of YouTube videos of R77s on Fz8. Watch and listen. I have the R77-D and I am very happy with it, because it's not overly loud - especially while cruising at highway speeds where excessive noise could get HORRIBLY ANNOYING! lol.
The R77 is louder, and I'd say would be a pretty could tone and noise level. I am sure there are louder exhausts, but I can only think those people generally just bum about their towns and make noise as a statement.
Take a look at the Vance & Hines CS-1 Blackout too.