That would end up being defined by local legislation. Each municipality deciding what it didn't accept so long as the local standard didn't step on a state or Federal standard.
Anyone who considered the continuing march of tech had to know that tools like this were possible. There just needed to be a match to the proverbial kindling to make it happen. The article also explains what that match was:
"Electrical engineer Mark Nesdoly invented the snare after a loud motorcycle awoke his sleeping daughter one night"
So someone in a neighborhood who may have thought it was just oh so fun to set off car alarms or hear the crack of his own exhaust set the wheels in motion. And to that fellow rider all who shall enjoy the fruits of his effort can say.... bite me.
Do it yourself, or have it legislated...right or wrong (depending on which end you're on)...it's gonna' happen. The prudent thing to do is be reasonable, on both sides, but all those "it's my freedom of choice, and don't f with that" are gonna' lose. If it's perceived as too loud, by whomever is "in charge" you're gonna' get screwed if you do otherwise. Period.
Edited: Don't EVER forget...we, as bike riders, are in the MINORITY. What happens to minorities, in general? If they don't police themselves?