Ride a HD for 5yrs, I bet you find quite the opposite. Direction of sounds plays a huge role.
There is a little gray area here but I am no one to argue with science, so as it pertains to this thread, if the OP's exhaust volume level is under that measurable limit, is there are problem on public roads?
No, not at 3pm unless communication between people has occurred and no laws are broken, however some common neighborly courtesy/common sense should be observed at all times. Hence maybe that is why the OP's garage door was closed? And it doesn't address the "unknown" day sleepers as as a rider passes through the streets of non-neighbors. Maybe those residence should push for a city noise ordnance. Between trucks, ricers and other noisey road travelers, I don't see much difference.
And singling out bikes would be unfair. In the end, I feel that if one was to work a really late shift, increased noise levels is something that that person will just have to get used to it as there is no real solution to that specific problem that works for everyone everywhere.
I think you and I are on the same page that "Loud Pipes Saves Lives" smeared on everything is absurd. Very much of this subject is comparative to HIGH VIS gear. It don't matter if they don't look. If it increases my chances of being on someones radar, like playing the lotto, one stands a better chance of being a winner but certainly doesn't guarantee safety.