Both the FAA and the U.S. Department of Housing and Urban Development consider exposure levels higher than DNL 65 to be incompatible with residential land use. DNL is the Day-Night average sound Level expressed (in decibels) as a 24-hour average. An annual average of DNLs is used by the FAA to describe airport noise exposure. Areas with noise impacts less than 65 DNL are considered "compatible" with residential use; areas at or above 65 DNL are designated "incompatible" with residential use.
Massport reports population counts by 5-decibel increments of exposure each year by community to track Logan Airport's noise environment changes over time from neighborhood to neighborhood. The counting methodology is updated over time to reflect changes in population using U.S. Census data.
Table for Noise Exposed Population by Community 1990, 2000, 2005 and 2011-2015