Code of Maryland Regulations › Title 11 - DEPARTMENT OF TRANSPORTATION › Subtitle 03 - MARYLAND AVIATION ADMINISTRATION › Chapter 11.03.03 - Airport Noise Control Program › Section 11.03.03.01 - Definitions

Current through Register Vol. 51, No. 14, July 12, 2024
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).