The Program can only provide sound insulation improvements to properties located inside the Noise Remedy Boundary that exists when installation of the improvements begins. The Noise Remedy Boundary is established under FAA guidelines using noise modelling and the FAA’s required noise metric known as Day-Night average sound Level or “DNL”. DNL is calculated as a 24- hour average (measured in decibels) with nighttime noise weighted at a level 10 times that of daytime noise.
The FAA has determined that a property must be located within an approved boundary area with a DNL level of at least 65 dB DNL to be potentially eligible for sound insulation. A DNL noise contour is produced using sophisticated noise modelling software using the FAA-required method, and this contour forms the basis for the Noise Remedy Boundary.
