I don’t think Hollywood stereotypes of biker gangs was a predominant motivator for the Noise Control Act of ‘72.

This is a regulation that generally regulates noise for all kinds of things, from appliances to airplanes.

Their stated rationale is: https://www.law.cornell.edu/uscode/text/42/4901

I think Hollywood wasn't motivating anti-biker attitudes, just the opposite. Hollywood made these movies because the subject was of interest to the public. Motorcyclists were already notoriously antisocial by 1972, and that public sentiment probably informed the Noise Control Act of '72.