Relative contributions of highway and neighborhood sources to outdoor and indoor residential sound levels

An unusually large and detailed database of simultaneous indoor and outdoor, A- and C-weighted traffic noise levels, sampled at half-second intervals, was assembled from continuous week-long measurements at more than 300 occupied suburban residences at distances as great as 2000 meters from a heavily traveled, limited access highway. Even at relatively short ranges from the highway, indoor sound levels when residents were home and awake were typically controlled by sounds of domestic activity rather than by those of highway traffic, local street traffic, or other outdoor neighborhood sources. Outdoor sound levels were poorly correlated with corresponding time series of indoor sound levels when residents were home and awake. The range at which highway noise predominates over other neighborhood noise sources - a “region of influence” of highway traffic noise on outdoor ambient levels - extended only about 300 meters from the highway. A straightforward statistical summation of independent highway and local street traffic noise processes accounts well for measured outdoor noise levels as functions of distance from the highway and of time of day.