Why isn’t noise abatement designed to reduce noise levels below the NAC?
The noise abatement criteria (NAC) identifies the noise level at which noise abatement should be evaluated. It is not a noise abatement goal. The objective of noise abatement is to achieve a noise reduction that will result in a noticeable difference from the unabated traffic noise levels and can be implemented in a cost effective way. In typical noise abatement evaluations, a substantial noise reduction is considered to be an 8-dBA traffic noise reduction. The following table demonstrates this noise reduction goal for two sites.
