Definition of loud pipes: Often, but not limited to Harley riders, who like to rev their bikes in a bid to let everyone know around them that they are riding a bike with a loud (excessive), exhaust pipe - look at me!
I believe that there is a difference between a loud and excessive pipe sound. I once had a Yamaha 1000 with an aftermarket exhaust that was definitely louder than the stock, but under no circumstances was excessive. Hence, there was still a sweet sounding note emitted from the rear, but didn't catch the attention of bystanders in a two kilometre radius.
I personally don't like the excessive noise made from big, unfriendly road bikes, and yes there are some adventure bikes that have a similar (baffle free), sound that frightens off any wildlife or human inhabitant in the near vicinity - noise pollution!
"Men do not stop playing because they grow old, they grow old because they stop playing."
O. W. H.