Boulder, CO Noise Ordinances: Decibel Limits (2026)

Section 5-9-3(b) of the Boulder Revised Code sets the decibel ceiling by the zoning district of the property where the sound is received, not where it starts. A residential receiver is protected to 55 dBA from 7 a.m. until 11 p.m. and 50 dBA from 11 p.m. until 7 a.m. the following day. Mixed use and other districts get 65 dBA and 60 dBA. Industrial districts get 80 dBA and 75 dBA. Section 5-9-2 defines residential as land zoned RE, RH-1 through RH-5, RL, MH, RM, RMX, RR-1 or RR-2, commercial as A, BCS, BMS, BC, MU, P, BT, BR or DT, and industrial as IG, IM, IS or IMS. A new district created without amending the chapter is governed as the existing district it most closely resembles, and a true tie goes to the category with the lower allowable decibel levels.

The rule reaches anyone who operates a vehicle, machine or device, carries on an activity, or promotes or facilitates an activity that makes sound over the limit. A moving vehicular source in the public right of way is carved out of this table and handled by section 5-9-4.

Where the reading is taken matters. Sound from a source on private property is measured at or inside the property line of property other than the one holding the source. Sound from a source on public property is measured on the receiving property so long as the reading is at least twenty-five feet from the source, or at or inside the line of receiving property other than the public property holding the source. A leasehold counts as the lessee's property, and its boundary is treated as a property line except against adjacent land the lessee also owns. Every measurement must come from a sound level meter meeting ANSI S1.4-1974 Type I or Type II, and the manufacturer's published statement of compliance is prima facie evidence that the meter qualifies.

Construction under a building permit gets a relaxed standard. From 7 a.m. to 5 p.m., sound from work of any type is deemed received in an industrial zoning district, so the industrial limits govern even beside homes. From 5 p.m. until 9 p.m., sound from light construction work received in a residential zone is deemed received in a commercial zoning district. Light construction means hand tools and power tools of no more than five horsepower, and it excludes power actuated fastening devices such as nail guns. Under no circumstances is amplified sound treated as construction work activity.