I found the following for Michigan:
Maximum Sound Level Maximum allowable A-weighed sound levels as measured from 50 feet (Sec. 257.707c): 86dBA at speed over 35mph; 82dBA at speed less than 35mph; 95dBA under stationary run-up test at 75 inches.
AFAIK, based on listening to bikes in certain towns on "bike night", cops don't do anything with that.
