Sun Prairie, WI Noise Ordinances: Decibel Limits (2026)

030 sets maximum permissible sound pressure levels for stationary noise sources, measured at the property line of the affected lot. The table splits the city into three zones: residential lots may not exceed 65 decibels in daytime hours and 50 decibels at night, commercial zones are capped at 70 decibels day and night, and every other zoning district tops out at 75 decibels regardless of the hour. The section also treats ambient noise as a factor: if the measured sound exceeds the surrounding ambient noise by 5 decibels in any octave band, it is designated excessive even if it falls under the table limit, and pure tones or impulsive noises get five rating numbers subtracted before comparison.

In residential districts, the person responsible for a violation is ordered by the city's monitoring officer to reduce the sound pressure to acceptable levels immediately. Noise measurement is standardized: readings are taken with a sound level meter at the nearest lot line to the complaint, held at least three feet above the ground and at least three feet from any wall or reflective surface. Property owners are not without recourse: the common council may grant an exemption on a showing of substantial hardship, and evidence of reasonable technological fixes counts toward an exemption for existing industries. 040).