Md. Code Regs. 11.03.03.01 - Definitions
A. Acoustic
Terminology.
(1) "Annual day-night (average)
sound level (Ldn)" means for locations in the neighborhood of an airport, the
day-night (average) sound level, in decibels, resulting from the effective
annual average daily traffic and the utilization of runways and flight paths
that affect the noise exposure at the location in question.
(2) "Average sound (noise) level (Leq)" means
the constant sound level, in decibels, which, in a given situation and time
period, would convey the same sound energy as does the actual time-varying
sound during the same period. A-weighting is understood. Unless otherwise
qualified, the average is reckoned over a 24-hour day, from midnight to
midnight. The mathematical formulation of average sound level is as follows: If
LA(t) represents the value of instantaneous A-weighted sound pressure level
fluctuating with time, (See Formula Table below) where t1 and t2 are,
respectively, the times marking the beginning and end of the observation period
over which the average is reckoned.
(3) "Contours of equal noise exposure" means
the locus of points on the ground with a given noise exposure.
(4) "Data range" means for a set of 24-hour
measurements of Ldn, the difference between the highest
value and the lowest value of Ldn in decibels.
(5) "Day-night (average) sound level
(Ldn)" means the average sound level, in decibels,
reckoned over a 24-hour day with a 10 decibel weighting applied to the noise
occurring during the nighttime period; that is, noise levels occurring at night
are treated as though they were 10 dB higher than they actually are. The
mathematical formulation of day-night sound level is as follows:
See Formula Table below.
(6) "Daytime (average sound level
(Ld)" means the average sound level, in decibels, for
the 15 hour time period between 0700 and 2200 (7a.m. to 10p.m.). The
mathematical formulation for daytime sound level is as follows:
See Formula Table below.
(7) "Decibel (dB)" means a division of the
logarithmic scale customarily used to express the ratio of two like quantities
proportional to power or energy.
(8) "Decibel scale" means a logarithmic scale
used to express the ratio of two like quantities proportional to power or
energy. The ratio is expressed on the decibel scale by multiplying its common
logarithm by ten.
(9) "Hourly
(average) sound level, (Lh)" means the average sound level, in decibels, for a
1-hour period, usually reckoned between integral hours. There would be 24 such
values per day. The mathematical formulation of hourly sound level is, for
example:
See Formula Table below.
(10) "Level (L)" means the ratio, expressed
on the decibel scale, of two like quantities, the second of which is a standard
reference quantity.
(11) "Nighttime
(average) sound level (Lp)" means the average sound level, in decibels for the
9 hour period from 2200 to 0700 the next morning (10 p.m. to 7 a.m.). The
mathematical formulation for nighttime sound level is as follows:
See Formula Table below.
(12) "Sound level (noise level) (LA)" means
the quantity in decibels measured by an instrument satisfying the requirements
of American National Standard Specifications for Sound Level Meters, S1.4-1971,
or its latest revision; that is, the frequency-weighted sound pressure level
obtained with the standardized "fast" dynamic characteristic and the "A"
frequency weighting of the sound level meter.
(13) "Sound pressure (p)" expressed in
micropascals, means a fluctuating pressure superimposed on the static
atmospheric pressure in the presence of sound. Unless qualified, the term means
root-mean-square sound pressure.
(14) "Sound pressure level (Lp)" means the
squared ratio, expressed the decibel scale, of the sound pressure under
consideration to the standard reference pressure of 20 micropascals (= 20
micronewtons/square meter or 0.0002 dynes/square centimeter).
B. Airport Terminology. The
following terms refer to physical and operational characteristics of airports:
(1) "Airport" means any airport licensed by
the Administration.
(2) "Airport
operator" means the licensee, or any person who is designated by the licensee
as airport operator and who is made responsible to the licensee for the
supervision and operation of the airport.
(3) "Effective annual average daily traffic
"EAADT" means the standard daily volume of air traffic typifying airport
operations, which is determined as follows:
(a) Calculate the average number of airport
operations for the 10 busiest days of the year:
See Formula Table below.
N1 through N10 being the number of operations on the 10 busiest days;
(b) Eliminate
from further consideration the number of days and the number of operations at
the airport which are less than N/2;
(c) The effective annual average daily
traffic is the average number of daily operations for all the remaining days of
the year.
(4) "Flight
operation" means a single take-off, landing or flyby. (A "touch-and-go" counts
as two operations.)
(5) "Licensee"
means the person, firm, agency, or political subdivision to whom the airport
license is issued by the Executive Director.
(6) "Start of takeoff roll" means the
position on a runway where an aircraft starts to accelerate in taking
off.
(7) "Threshold" means that
position on a runway, seen from the approach end, designated as the first point
where a landing is permitted. The first point does not necessarily coincide
with the start of paving.
(8)
"Utilization" means the percentage of the total number of a specific category
of operations, on an annual basis, that uses a particular runway or flight
track.
C. Other
Terminology. Other terms concerning airport noise regulation, but not
specifically related to airports or acoustics, are as follows:
(1) "Certified noise abatement plan" means a
noise abatement plan accepted by the Executive Director for implementation by
an airport operator.
(2) "Daytime"
means 0700 to 2200 hours (7 a.m. to 10 p.m.).
(3) "Nighttime" means 2200 to 0700 hours (10
p.m. to 7 a.m.).
(4) "Noise
abatement plan" means a detailed program of changes in airport operation which
has as its goal the reduction or elimination of impacted land use areas.
Notes
Regulation .01C amended effective October 16, 2000 (27:20 Md. R. 1840)
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