more than 3 violations of the limits contained
in this subparagraph in a 24-hour period.
(C) DAY-NIGHT AVERAGE SOUND LEVEL.—
If the day-night average sound level, with com-
bined aviation and nonaviation sources, exceeds
45 decibels, then aviation activity may not con-
tribute more than 3 decibels to such sound
level.
(3) PAST AIRSPACE TRAFFIC CHANGES.—The
Administrator shall review airspace traffic changes
made by the Administrator which continue to be
subject to significant complaint or controversy and
shall take such actions as may be necessary to en-
sure that such air traffic changes do not result in
increases in aviation noise which violate aviation
noise limits contained in paragraph (2).
(d) DETERMINATION OF VICINITY OF AIRPORT.—
(1) ALTERNATIVE BOUNDARIES.—In the event
that operations procedures of an airport result in a
ground noise distribution substantially different
from the geographic area defined in section 4(10),
an airport operator may, on or before the 180th day
following the date of the enactment of this Act,
transmit to the Secretary for approval alternative
boundaries of the vicinity of the airport which con-
form to the ground noise distribution of the airport;
except that the geographic area enclosed by such al-
ternative boundaries may not include an area with
a day-night average sound level of less than 60 deci-
bels for the 1-year period ending on the date of the
enactment of this Act.
(2) ACQUISITION OF PROPERTY.—In the event
that an airspace traffic change or other action
makes it unfeasible or impracticable to meet the
sound level limits contained in subsection (b) within
a residential area, then such area may be added to
the area considered to be in the vicinity of the air-
port upon acquisition of the property or by acquisi-
tion of easements to the property by the airport op-
erator or the Secretary of Transportation.
(e) REPORT.—Not later than 1 year after the date
of the enactment of this Act, the Secretary shall transmit
to Congress a report containing the plan to be developed
pursuant to subsection (a)(1), and a description of actions
taken with respect to airspace changes pursuant to sub-
section (b)(3), together with recommendations for appro-
priate administrative and legislative actions.
SEC. 4. RESPONSIBILITY OF SECRETARY OF TRANSPOR-
TATION.
In complying with this Act, the Secretary of Trans-
portation shall assume responsibility for all non-military
aviation activity, within and outside controlled airspace,
and shall regulate such activity to ensure compliance with
the requirements of this Act in normal circumstances.
SEC. 5. DEFINITIONS.
For the purposes of this Act, the following definitions
apply:
(1) ADMINISTRATOR.—The term ‘‘Adminis-
trator’’ means the Administrator of the Federal
Aviation Administration.
(2) AIRSPACE
TRAFFIC
CHANGE.—The term
‘‘airspace traffic change’’ means a change in aircraft
flight paths, operating procedures, nature of aircraft
traffic, and quantity of aircraft traffic which is ap-
plicable in normal circumstances.
(3) AVERAGE SOUND LEVEL.—The term ‘‘aver-
age sound level’’ means the level, in decibels, of the
mean-square, A-weighted sound pressure during a
specified period, with reference to the square of the
standard 
reference 
sound 
pressure 
of 
micropascals.
(4) BACKGROUND
SOUND
LEVEL.—The term
‘‘background sound level’’ means the hourly average
sound level, in decibels, measured at a site rep-
resentative of a relatively quiet residential location
within an area (with aircraft noise contributions ex-
cluded).
(5) DAY-NIGHT AVERAGE SOUND LEVEL.—The
term ‘‘day-night average sound level’’ means the 24-
hour average sound level, in decibels, for the period
from midnight to midnight, obtained after the addi-
tion of 10 decibels to sound levels during nighttime
hours.
(6) NIGHTTIME HOURS.—The term ‘‘nighttime
hours’’ means the periods between midnight and 7
a.m. and between 10 p.m. and midnight local time.
(7) NORMAL CIRCUMSTANCES.—The term ‘‘nor-
mal circumstances’’ means all circumstances other
than unusually adverse weather and emergency cir-
cumstances.
(8) SECRETARY.—The term ‘‘Secretary’’ means
the Secretary of Transportation.
(9) SINGLE EVENT MAXIMUM SOUND LEVEL.—
The term ‘‘single event maximum sound level’’
means the level, in decibels, of the maximum A-
weighted sound pressure during an aircraft over-
flight obtained using a standard sound level meter
under a slow response setting.
(10) VICINITY OF AN AIRPORT.—The term ‘‘vi-
cinity of an airport’’ means the geographic area sur-
rounding an airport established before the date of
the enactment of this Act described nominally as fol-
lows:
(A) The area extending in all directions a
distance of 1.5 miles from each runway estab-
lished before such date of the enactment.
(B) The rectangular area defined by draw-
ing a straight center line a distance of 4 miles
from the end of each runway established before
such date of the enactment in the direction of
heaviest traffic and extending 1.5 miles per-
pendicular from the center line on each side of
such runway.
Æ