Noise ordinances are among the most frequently enforced and most frequently challenged local regulations.

Objective standards measured in decibels at a defined location — the property line, or a specified distance — with limits varying by district and time of day, and a defined measurement methodology and equipment standard. These are far more defensible than subjective standards.

Plainly audible standards measured at a stated distance are permissible in many jurisdictions and are more vulnerable, since they depend on the officer’s perception.

Subjective standards. Prohibitions on unreasonable, annoying or disturbing noise are challenged for vagueness, and survive only where narrowed by objective criteria or by a reasonable person qualifier tied to specific factors.

Content neutrality. Amplified speech may be regulated for volume, hours and location, and not by reference to the message. Exemptions for particular events or speakers create content discrimination problems.

Exemptions. Emergency vehicles, construction within stated hours, permitted events, agricultural operations, and religious bells, each of which should be justified by something other than the identity of the speaker.

Enforcement. Trained officers, calibrated meters, and recorded readings. Prosecutions failing for lack of calibration records are common.