A noise ordinance is a local law that prohibits noise that becomes a nuisance. Typically, a noise ordinance is codified in municipal code.
Noise ordinances give the police the power to request someone to not make so much noise and a city attorney the power to prosecute a resident for violating the noise ordinance.
A noise ordinance allows a citizen who is disturbed by noise to make an official complaint to the municipality where the citizen lives. However, before issuing a noise ordinance, law enforcement will usually simply ask that the person making the noise quiet down.
The penalty for violating a noise ordinance is usually a fine. In defending against the prosecution of a noise ordinance, defendants sometimes resort to free speech or other constitutional protections.