People in the off road world are finally coming around to the noise issues, but I think it will be a long time before the street (*cough*Harley*cough*) crowd breaks tradition to accept it.
I'm part of an off road racing organization where we must pass sound check for every race. 96 dB is the current limit, because that's what Arizona law currently is. 4 strokes are DEFINETELY harder to pass than the 2 strokes. Most 4 strokes can barely squeek by, and any of the 4 stroke MX bikes need a quite silencer/tip to pass. We've had guys show up throwing 105-110 dB range. I am still amazed at the difference sound-wise between our races and going to the local MX. Some of those bikes are painfully loud there, because no one cares! Noise = power to most people!
Quite bikes can be done, but it's going to be hard to get the consumer to accept that. Yamaha made a big leap going to a mechanical muffler on the YZ450F, cutting sound a large amount. Guess what everyone does? Ditches that silencer for an aftermarket one, because you can get 3-4 hp that way. Never mind that test riders and guys in the know actually say you can pull faster lap times with the smoother, more linear power of the stock silencer. I at one time set my old KX125 up to be ubber quiet. Quiet silencer, airbox baffle, lots of foam everywhere (around airbox, above lid/baffle, under engine, etc). It actually blew only 78dB on the race mic. There was still a lot of sound coming from the expansion chamber, but it was a big impovement, and still had plenty of power for a B level off road racer.
Anyway, in 10 years we won't have to worry about this because either
A) All forms of recreational fun will be shut down
or
B) Electric bikes will catch on. KTM has one in the works, and I'm ready for it.
