If you can hear them moving, your mufflers are no good,lol
Ok seriously, I have never heard mine.
But sometimes the flyweights don't all seem to return to the same resting point, and then I notice a small vibration. This occasionally happens at cruising speed, 2200rpm/64mph. I just clutch it and blip the throttle, then it's all better.
But if you take either of them out and shake them, then you can hear stuff rattling around.