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

The limits apply at the receiving property, meaning enforcement officers measure sound at the line of the neighboring parcel, not at its source, so the applicable ceiling is whichever land use is actually receiving the noise. Readings are taken with a sound level meter meeting American National Standards Institute S1-4-1971 Type 2 specifications, using A-weighting unless another network is specified, and § 260-3(D) lets the county rely on measurement techniques recommended by the Maryland Department of the Environment, which may reference ANSI, ASTM, SAE, or EPA standards.

Decibel itself is defined in § 260-2 as ten times the logarithm of the ratio of a sound pressure to a standard reference pressure of 20 micropascals. The four-tier structure, industrial at a flat 75 dBA around the clock, commercial dropping from 67 to 62 dBA, and residential dropping from 60 to 50 dBA overnight, was set when the chapter was adopted March 7, 2005 by Bill No. 2004-01 and last amended September 7, 2010 by Bill No. 2010-11, which also added the RECEIVING PROPERTY definition covering apartments, condominiums, and cooperative units.