Many of todays vehicles are coming from the factory with high performance stereos and many of those that do not are outfitted with after market systems with lots of power.
Wisconsin State Statute 346.94(16) addresses loud, amplified noises including music, coming from a motor vehicle. This Statute like all traffic Statutes is adopted by Wauwatosa Ordinance 11.04.010. 346.94(16)/11.04.010 states that any amplified sound coming from a motor vehicle that can be heard from a distance of 75 feet or greater is a violation. The first offense carries a forfeiture of $96.40; second offense in a twelve month period carries a forfeiture of $172.00.
Of special note to parents and others who may loan their vehicles out, owners of a vehicle can be cited for this violation even if they are not in the vehicle at the time of the offense. So as a registered owner who may even be out of town while your vehicle is be driven by someone with the music too loud can receive a ticket for $96.40.