NOISE CONTOURS

DNL Noise Contours

A Noise Contour is a line on a map that represents equal levels of noise exposure. Nantucket uses the FAA computer model, the Integrated Noise Model (INM), to calculate annual noise contours. The number of annual flights, aircraft types, flight tracks, runway use and time of day are critical inputs to the noise contour model.

The following maps present the modeled day/night noise level (DNL) contours for 2004 actual operations shown in 5-decibel increments for DNL values of 60, 65, 70, 75 and 80.

The FAA defines significant noise exposure as and area within the annual 65 DNL noise contour. Federal guidelines, adopted for appropiate land use planning, identify incompatible residential land use within an annual average noise exposure of 65 DNL or higher.

As airport operations increase toward a peak during the summer months, so does airport noise. In order to visualize how the increased summer activity affects the noise contours, we have prepared two cases:

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1). 2004 Annual Average Noise Contours

2). 2004 Summer Peak Noise Contours

These noise contour cases were prepared using the Town of Nantucket Geographic Information System (GIS) 2003 aerial photo base map. Noise contours have been overlaid and color coded for ease of use.