Montgomery County, MD Noise Ordinances: Decibel Limits (2026)

MoCo Code Chapter 31B establishes maximum permissible sound levels measured at the receiving property boundary. Residential receiving properties have the lowest thresholds, while commercial and industrial areas permit higher decibel levels. Nighttime limits (9 PM to 7 AM) are approximately 5-10 dB lower than daytime standards to account for lower ambient noise. Measurements are taken using A-weighted decibel scale (dBA) by trained Department of Environmental Protection staff or Montgomery County Police. Short-duration impulse sounds such as car doors and trash collection may be evaluated differently from continuous noise sources. The county considers both the measured decibel level and the character of the sound (tonal, impulsive, or broadband) when evaluating complaints. Maryland Environment Article provides supplementary state noise authority. Background ambient levels are considered when evaluating whether a source exceeds standards, particularly in quieter suburban and rural areas like Poolesville and Damascus versus denser areas like Silver Spring and Bethesda.