10 rules for unincorporated Yellowstone County, Montana.
Verified from official government sources
Unincorporated Yellowstone County sets no numeric quiet-hours ordinance; your city governs. In Billings (the county seat), maximum noise levels drop to nighttime limits between 8:00 p.m. and 7:00 a.m. As a rule, avoid noise likely to draw a complaint during those hours.
Yellowstone County sets no county-wide construction-hours noise rule. In Billings, noise from home or building repair, construction, or grounds maintenance is fully exempt from decibel limits between 7:00 a.m. and 8:00 p.m. Outside that window, construction must meet standard limits or obtain a waiver.
In Billings, keeping any animal that unreasonably annoys people by continuous and habitual barking, howling, yelping, or whining is a public nuisance and a misdemeanor. Unincorporated Yellowstone County handles habitual barking through county animal control and Montana's public-nuisance law.
Billings City Code Sec. 4-404
Every person who keeps, feeds, harbors or allows to stay about any premises... any animal which unreasonably annoys or disturbs any person by continuous and habitual barking, howling, yelping, whining or other noise is guilty of maintaining a public nuisance.
Billings sets no leaf-blower ban. Grounds-maintenance noise, including leaf blowers and mowers, is exempt from decibel limits between 7:00 a.m. and 8:00 p.m. Motorized lawnmowers fitted with equipment-type mufflers are specifically exempt in those hours. No separate county leaf-blower rule exists.
Billings has no separate amplified-music curfew, but loud amplified sound that disturbs a neighborhood is unlawful under the general prohibition, and radiating sound above the district decibel limits is prima facie a public nuisance. Special events over the limit require a city waiver.
Aircraft noise is regulated by the FAA, not by Yellowstone County or Billings. Billings Logan International Airport (KBIL), city-owned and located in Yellowstone County atop the Rims, follows FAA-established noise-abatement procedures. Neither the county nor city sets an enforceable aircraft decibel limit.
Billings caps industrial-district noise at 90 dB(A), heavy commercial at 85 dB(A), and light commercial at 80 dB(A), measured at 25 feet or the lot line. Noise from production, processing, servicing, testing, and repair counts. At zone boundaries the lower limit applies.
Billings measures noise at 25 feet from the source (or the lot line) and sets maximum dB(A) by district: residential 65 day / 55 night, light commercial 80, heavy commercial 85, industrial 90. Exceeding the limit is prima facie a public nuisance. Unincorporated county land has no numeric limit.
Outdoor music in Billings must stay within the district decibel limits and the general noise prohibition. Permitted events in stadiums or parks, and special events, are exempt only if a city waiver has been granted. Unincorporated Yellowstone County sets no outdoor-music ordinance.
In Billings, a car sound system may not be operated so it is plainly audible 50 feet or more from the vehicle (Sec. 24-352). Statewide, Montana requires every motor vehicle to have a working muffler and bars exhaust noise over 95 decibels (MCA 61-9-403, 61-9-435).
Billings City Code Sec. 24-352
No driver or occupant of a motor vehicle... shall operate or permit the operation of a sound amplification system from within a motor vehicle so that the sound is plainly audible (heard) at a distance of fifty (50) feet or more from the motor vehicle.
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