The good thing about Harleys is that they don’t run half the time so in actuality you get 50% noise attenuation.
Here is a classic! He actually admits he likes loud pipes so he can push cars around!
“Based upon my own first hand experiences riding motorcycles, I can say without a doubt that Loud Pipes do save lives! I have been in many situations, particularly when I am splitting lanes, where revving my engine and making noise got cagers to notice me and make way.”
http://www.bikerlawblog.com/index.php/biker_laws/2006/11/29/do_loud_pipes_on_motorcycles_save_lives_