State law requires that a noise element be prepared as part of all city and county general plans. Noise elements are required to identify noise problems in the community and to work toward their resolution. The Marin County Noise Element has been prepared to meet the requirements of State law.

The first Countywide Plan Noise Element was adopted in 1975. It addressed noise generated by automobile traffic on highways. The updated Noise Element incorporates new information and concerns related to community noise exposure levels in the county. The purpose of the Element is to identify current and projected future noise levels from major sources, including Highway 101, the heliport adjacent to Richardson Bay, and the County airport at Gnoss Field (north of Novato). Based on the levels of noise from these sources and from construction activity and other sources, the Element identifies programs to help mitigate significant noise problems in the community.

The Element includes objectives, policies, and implementation programs which fall in one of two categories: (1) locating and designing new development to minimize exposure of residents and workers to excessive noise levels, and (2) maintaining acceptable noise levels in existing developed areas. Policies in the first category include guidelines for noise levels for residential, commercial, and industrial development. These guidelines establish the following threshold outdoor noise levels at which an acoustical analysis must be performed: 60 decibels (dbA) LDN for residential developments, 65 dbA LDN for office and commercial developments, and 70 dbA LDN for industrial developments. Policies in the second category include standards for maintaining acceptable noise levels in areas with existing residential, commercial, industrial, and institutional uses. New developments will be analyzed for their impacts on these existing uses.