Montgomery County Noise Ordinance: Decibel Limits, Hours, and Fines

The Montgomery County noise ordinance, set out in Chapter 31B of the county code, caps how loud sound can be at a neighbor’s property line and gives residents a formal way to complain when someone exceeds those limits. Residential areas are held to 65 dBA during the day and 55 dBA at night, with separate rules for construction sites, a full ban on gas-powered leaf blowers, and a broader “noise disturbance” standard that can reach annoying sounds even when a meter reads under the cap.¹

Decibel Limits by Zone and Time

Section 31B-5 measures sound on the A-weighted scale (dBA), which reflects how the human ear hears sound. The county splits receiving properties into just two categories:¹

Residential: 65 dBA daytime, 55 dBA nighttime.
Non-residential: 67 dBA daytime, 62 dBA nighttime.

There is no separate industrial category. Commercially or industrially zoned properties fall under the non-residential limits. Enforcement officers take the reading at the property line of whoever is receiving the noise, and when sound crosses between zones, the limit of the receiving property controls.²

When Daytime and Nighttime Start

The clock matters. Daytime runs from 7:00 a.m. to 9:00 p.m. on weekdays and from 9:00 a.m. to 9:00 p.m. on weekends and holidays. Everything outside those windows is nighttime, and the stricter limits apply.²

That two-hour weekend delay is easy to miss. A landscaping crew that legally starts at 7:00 a.m. on a Tuesday is bound by the nighttime limit if it starts the same equipment at 7:00 a.m. on a Saturday. In a residential area, the nighttime cap drops a full 10 dBA below the daytime cap, roughly a halving of perceived loudness.¹

Construction Noise Rules

Construction gets its own section because heavy equipment routinely exceeds standard limits. Under Section 31B-6:

Weekdays, 7:00 a.m. to 5:00 p.m.: 75 dBA without an approved noise-suppression plan, or 85 dBA if the Department of Environmental Protection has approved a plan for the project.
All other times: the regular Section 31B-5 limits apply.

Construction noise is measured at least 50 feet from the source, on the receiving property where the sound is loudest.³

The real pressure on contractors comes from stop-work orders. A second construction noise violation within 30 days can shut the site down for three working days, a third within 60 days brings a five-day shutdown, and a fourth or subsequent violation within 120 days triggers a seven-day shutdown per violation.⁴ Both the person directly causing the noise and the person managing or supervising the site are jointly liable, so a general contractor cannot push responsibility entirely onto a subcontractor.

Gas-Powered Leaf Blower Ban

All leaf blowers, regardless of power source, are limited to 70 dBA measured at 50 feet. The larger change is a full ban on gas-powered models. Sales became illegal on July 1, 2024, and use became illegal on July 1, 2025.⁵

Agricultural producers are exempt. For everyone else, including commercial landscapers, enforcement runs on a witness-complaint model: the Department of Environmental Protection must receive a complaint from at least one witness within seven days of the alleged violation before an officer can issue a citation.⁵

Sounds That Break the Rules Without a Meter

Not every noise problem shows up on a decibel reading. The ordinance also prohibits “noise disturbances,” defined as sound that is:

Unpleasant, annoying, offensive, loud, or obnoxious;
Unusual for the time of day or location where it occurs; or
Harmful to health, comfort, safety, the reasonable enjoyment of property, or the conduct of business, based on its loudness, duration, or character.

A persistently barking dog, a blaring television audible across a property line, or a late-night engine repair can qualify even if a meter never crosses the numerical cap. The Department of Environmental Protection describes this standard as “more subjective” and grounded in “the observations and testimony of witnesses.”⁶ That subjectivity works both ways: it reaches annoying sounds that slip under the cap, and it also means outcomes depend heavily on how clearly a complainant can describe what happened.

What the Ordinance Does Not Cover

Section 31B-10 exempts several categories entirely:

Emergency operations by fire and rescue, police, public utilities, and their contractors.
Agricultural machinery used and maintained per manufacturer specifications.
Unamplified sound from sports, entertainment, parades, carnivals, and public celebrations between 7:00 a.m. and 11:00 p.m., provided the event has the required permit or license.
Any noise already governed by a stricter state or federal regulation.

⁴

The County Executive can also exempt routine daytime residential activity, such as home workshops, power tools, and lawn equipment used per manufacturer specifications. That carve-out does not cover working on a vehicle that is not registered for road use.⁴

Motor vehicle noise sits outside Chapter 31B. Motorcycles, dirt bikes, ATVs, and modified exhausts are handled under the state motor vehicle code and enforced by police, not the county noise ordinance.⁶

Waivers for Events and Projects

When something legitimately cannot fit within the limits, Section 31B-11 allows two waivers from the Director of the Department of Environmental Protection:

Temporary waiver, for a specific event where public benefit outweighs the noise impact. The Director must give public notice to affected households and cannot approve the waiver until at least 10 days after that notice. Temporary waivers last a maximum of 30 days and can be renewed no more than twice.
General waiver, for situations where compliance is impractical and would create undue hardship. The Director schedules a public hearing within 60 days, and the applicant must advertise the hearing in a local newspaper and post a sign at the site at least 30 days beforehand.

⁷

Both waivers require the applicant to use the best reasonably available technology and strategy to reduce noise. Filing a waiver request does not suspend the rules while the application is pending, so allow time before the event.⁷

How To Report a Violation

Where you report depends on when the noise is happening. During regular business hours, file a complaint with MC311 online or by phone, or submit a service request through the Department of Environmental Protection’s website.⁸ After business hours, call the police non-emergency line at 301-279-8000.⁶

For sporadic noise or incidents no officer witnesses in person, the county offers a “two-party noise complaint form” that lets a resident file a formal complaint based on their own observations, serving as the witness. The form is on the DEP website.⁶ Log the dates, times, duration, and nature of the sound. Vague complaints are harder for officers to act on.

Penalties

A violation of Chapter 31B is classified as a Class A civil violation, and each day the violation continues counts as a separate offense.⁴ Class A violations in Montgomery County typically carry fines starting at $500 for a first offense and increasing for repeat violations. Construction violations under Section 31B-6 are treated as a separate offense on top of any other Chapter 31B violation arising from the same incident, so a noisy construction site can accumulate multiple penalties from one event, on top of the stop-work exposure described above.

1
American Legal Publishing Corporation. Montgomery County Code – Sec. 31B-5 Noise Level and Noise Disturbance Violations
2
American Legal Publishing Corporation. Montgomery County Code – Sec. 31B-2 Definitions
3
American Legal Publishing Corporation. Montgomery County Code – Sec. 31B-6 Noise Level and Noise Disturbance Standards for Construction
4
Montgomery County, MD Noise Ordinance. Montgomery County Code Chapter 31B – Noise Control
5
American Legal Publishing Corporation. Montgomery County Code – Sec. 31B-9 Leaf Removal Equipment
6
Montgomery County Department of Environmental Protection. Noise Control
7
American Legal Publishing Corporation. Montgomery County Code – Sec. 31B-11 Waivers
8
Montgomery County Government. Noise Control Ordinance Information