Noise Ordinances in Boulder, CO

If you live in Boulder or are thinking about moving there, noise ordinances are one of those things you probably won't think about until they affect you directly. Boulder has 8 specific rules on the books covering different aspects of noise ordinances, and some of them might surprise you.

Quiet Hours

Boulder's nighttime noise curfew runs 11 p.m. to 7 a.m. Under Boulder Revised Code § 5-9-6(b), anyone on public property in a residential district during those hours is barred from yelling, screaming, shouting, cheering, or singing louder than normal conversational speech. A related law, § 5-9-5, lets residents get an official warning issued against a repeat noisy neighbor at any hour.

Key details: Curfew hours: 11 p.m. to 7 a.m.. Where it applies: Public property in a residential district. Standard: Louder than normal conversational speech. Related home rule: §5-9-5 requires a prior warning first. Penalty: Up to $2,650 fine, 90 days jail.

A § 5-9-6(b) violation is a municipal offense under the citywide general penalty, Boulder Revised Code § 5-2-4: a fine of up to $2,650 and up to ninety days in jail per violation, or both. Boulder Police respond to nighttime noise complaints and may issue a citation on the spot for public-property shouting or singing that exceeds normal conversational volume during curfew hours.

Aircraft Noise

Boulder controls aircraft noise and hazards through an Airport Influence Overlay Zone rather than a decibel ordinance. New construction near Boulder Municipal Airport may require a recorded avigation easement, and Zone One bars most new construction outright under Section 9-3-10.

Key details: Governing tool: Airport Influence Overlay Zone, four zones. Zone Four requirement: Recorded avigation easement on new construction. Zone One limit: No new construction except airport uses. Federal overlay: FAR Part 77 clear area, 500 ft wide, 7:1 slope. No variances: Section 9-3-10(g) bars any variance from this section.

Section 9-3-10(g) states no person shall violate any avigation easement or any zone prohibition, and specifically bars any variance from the section's requirements; violations are enforced through the quasi-judicial hearing procedure in Chapter 1-3 and are subject to the Section 5-2-4 general penalty of up to $2,650 per violation.

This is not one of those rules that cities tend to ignore. Boulder actively enforces its aircraft noise requirements.

Construction Hours

Boulder bars audible construction power tools in a residential zone between 9 p.m. and 7 a.m. under Boulder Revised Code § 5-9-7(b): if the tool can be heard off the property where it is being used, and the work needs or has a building permit, running it during that overnight window is a violation regardless of decibel level.

Key details: Curfew hours: 9 p.m. to 7 a.m.. Applies to: Power tools audible off-property, residential zone. Requires: Work under a required or issued building permit. Daytime treatment: Deemed industrial zone 7am-5pm (§5-9-3). Penalty: Up to $2,650 fine, 90 days jail.

A § 5-9-7(b) violation carries the citywide general penalty, Boulder Revised Code § 5-2-4: up to $2,650 and up to ninety days in jail per violation, or both. Boulder's code enforcement and police respond to after-hours construction noise complaints, and a contractor can be cited even if the same work would have been lawful during the day.

Decibel Limits

Boulder Revised Code § 5-9-3 sets fixed decibel ceilings by the zoning district where sound lands: 55 dBA by day and 50 dBA at night on residential property, 65/60 dBA on mixed-use and commercial land, and 80/75 dBA on industrial land. The night limit runs 11 p.m. to 7 a.m.; the day limit covers 7 a.m. to 11 p.m.

Key details: Residential limit: 55 dBA day, 50 dBA night. Mixed-use/commercial limit: 65 dBA day, 60 dBA night. Industrial limit: 80 dBA day, 75 dBA night. Night hours: 11 p.m. to 7 a.m.. Meter standard: ANSI S1.4-1974 Type I or II.

Boulder Revised Code Chapter 5-9 carries no standalone fine schedule, so a decibel violation defaults to the citywide general penalty in Section 5-2-4: up to $2,650 per violation and up to ninety days in jail, or both, with each day of a continuing violation charged separately. Boulder Police and the city manager's noise team investigate complaints and take sound-meter readings to document exceedances before issuing a summons.

Vehicle Noise

Boulder caps the noise a motor vehicle makes in the public right-of-way at 80 dBA (88 dBA for trucks rated 10,000 pounds or more), measured 25 feet from the vehicle, under Boulder Revised Code § 5-9-4. A separate rule, § 5-9-8, bans car stereos and amplifiers audible 25 feet away or that make vibrations people outside the vehicle can feel, at any hour, anywhere in the city.

Key details: Vehicle decibel cap: 80 dBA (88 dBA for 10,000+ lb vehicles). Measurement distance: 25 feet from the vehicle. Stereo/amplifier limit: Audible or felt 25 feet away, banned anytime. Muffler requirement: Must match factory noise output (§7-3-4). Muffler cutouts: Bypass or cutout devices prohibited.

A § 5-9-4 or § 5-9-8 citation carries the citywide general penalty of Boulder Revised Code § 5-2-4: up to $2,650 and up to ninety days in jail per violation, or both. Affirmative defenses exist for emergency vehicles, warning horns, alarms that self-silence within five minutes, and sound covered by a city manager street-closure or parade permit. Boulder Police issue the citations, typically after a 25-foot sound-meter or vibration check.

Leaf Blower Rules

Boulder bans lawn mowers, leaf blowers, and other power lawn or garden tools between 9 p.m. and 7 a.m. on private property within, or within 100 feet of, a residential district. Boulder Revised Code § 5-9-7(a) sets the curfew; a separate defense in § 5-9-3 otherwise shields lawn equipment used with a good muffler between 7 a.m. and 9 p.m.

Key details: Curfew hours: 9 p.m. to 7 a.m.. Covered area: Residential district plus 100-foot buffer. Covered tools: Lawn mowers, leaf blowers, power garden tools. Daytime protection: 7 a.m.-9 p.m. use shielded under §5-9-3. Penalty: Up to $2,650 fine, 90 days jail.

A § 5-9-7(a) violation is punished under the citywide general penalty, Boulder Revised Code § 5-2-4: up to $2,650 and up to ninety days in jail per violation, or both, with jail available only where the city proves the person acted intentionally, knowingly, or recklessly. Boulder Police and code enforcement respond to nighttime lawn-equipment complaints and can cite the operator directly.

Amplified Music & Outdoor Sound

Boulder limits how far amplified sound may carry from the property where it originates. Under Boulder Revised Code § 5-9-6(a), amplified sound in a residential district may not be audible 100 feet beyond the property line between 11 p.m. and 7 a.m., or 200 feet beyond it during the day; in a commercial or industrial district the nighttime distance limit rises to 150 feet.

Key details: Nighttime residential distance: 100+ feet beyond property line bars it. Nighttime commercial/industrial distance: 150+ feet beyond property line bars it. Daytime residential distance: 200+ feet beyond property line bars it. Night hours: 11 p.m. to 7 a.m.. Who is liable: Resident present or property owner/manager.

An amplified-noise violation under § 5-9-6(a) carries the general municipal penalty in Boulder Revised Code § 5-2-4: up to $2,650 and up to ninety days in jail per violation, or both. Because each resident present or each property controller can be charged, a single loud event, such as a party or outdoor concert, can produce multiple citations. Boulder Police confirm violations with a distance check from the property line.

Barking Dogs

Boulder Revised Code § 6-1-19 bars any animal guardian from letting a pet disturb the peace with loud, persistent or habitual barking, howling, yelping or similar noise, on or off the owner's property. Before anyone can be charged, the city must have already given a written warning about that specific animal within the prior twelve months.

Key details: Governing section: BRC § 6-1-19. Prior warning required: Yes, within 12 months. Trial proof standard: Two witnesses or corroboration. Cat exception: Applies if cat off premises. Maximum penalty: $2,650 fine or 90 days jail.

Before a citation can be issued, the city must first have sent a written warning about the same animal within the previous twelve months, and a conviction at trial needs two corroborating witnesses to the noise under Section 6-1-19(c). A conviction is punished under the general penalty in Section 5-2-4: up to $2,650 in fines, up to ninety days in jail, or both.

The Bottom Line

Boulder's noise ordinances rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Boulder is broadly strict or permissive.

Keep in mind that Boulder can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.