How is a Noise Exposure Map - Phoenix Sky Harbor International ...

Frequently Asked Questions
What are Noise Exposure Maps (NEMs)?
Noise Exposure Maps (NEMs) identify the noise exposure of the current operating conditions,
and projected future conditions. Included within this analysis is the operating conditions at the
airport including departure and arrival procedures, daytime and nighttime activity, touch and go
operations and helicopter activity. Aircraft noise is depicted on the NEMs as noise contours,
which show the average noise levels around the airport.
What is a Noise Exposure Map Update?
A Noise Exposure Map Update is designed to identify noise sensitive land uses surrounding an
airport for existing conditions and for five years in the future. For the purposes of Map Updates,
noise sensitive land uses are generally defined as residences or public use facilities (libraries,
places of worship, schools, nursing homes and hospitals) within the 65 Day-Night Average
Sound Level (DNL) noise contour, the area the FAA defines as impacted by aircraft noise.
How is a Noise Exposure Map Update Different from a Part 150 Study?
Like Noise Exposure Map Updates, Part 150 Studies identify noise sensitive land uses
surrounding an airport. However a Part 150 Study also recommends measures to both correct
existing incompatibilities and to prevent future incompatibilities. Both a Noise Exposure Map
Update and a Part 150 Study are guided by Federal Aviation Administration regulations found
in14 CFR Part 150.
What is the Integrated Noise Model?
The FAA has developed the Integrated Noise Model (INM) for evaluating aircraft noise impacts
in the vicinity of airports. The INM has been the FAA's standard tool since 1978 for determining
the predicted noise exposure in the vicinity of airports. The INM has been updated many times
since 1978 to include improved metrics and current aircraft databases. The FAA requires the use
of INM to develop noise exposure contours in Noise Exposure Map Updates. The INM utilizes
flight track information, types of aircraft using the airport, aircraft flight profiles, runway use and
terrain as inputs. The INM produces noise exposure contours measured in DNLs that are used for
land use compatibility maps.
What is the purpose of noise monitoring in a Noise Exposure Map Update?
Field measurements from the airport's permanent monitoring system and the temporary monitors
established as part of the Map Update were collected. The measurements were compared with
pre-existing database information related to aircraft noise level and performance characteristics
in the FAA's Integrated Noise Model. The information collected during the measurement
program included acoustical output as well as flight track data (the aircraft's three-dimensional
location) relative to the noise measurement site. This information was used to ensure that the
input data into the Integrated Noise Model was as accurate as possible.

What is DNL?
The Day-Night Average Sound Level metric describes the total noise exposure during a given
period. DNL is a metric used for predicting the average long term noise exposure on a
population. In computing DNL, an extra weight of 10 decibels (dB) is assigned to any sound
levels occurring between the hours of 10:00 p.m. and 7:00 a.m. This is intended to account for
the greater annoyance that nighttime noise is presumed to cause for most people. This extra
weight treats one nighttime noise event as equivalent to 10 daytime events of the same
magnitude.
Can the City of Phoenix restrict operations at Phoenix Sky Harbor International Airport?
No. The FAA is the only entity that can manage aircraft runway operations or aircraft in flight at
Phoenix Sky Harbor International Airport. Furthermore, as a recipient of grant funds from the
FAA, the City of Phoenix, operator of the Airport, must abide by specific FAA-imposed
obligations and conditions. One of these is that the City of Phoenix will not restrict or limit
airfield access based on noise.