D.C. Mun. Regs. tit. 20 § 2799
When used in Chapters 27 through 29 of this subtitle, the following words or abbreviations shall have the meaning ascribed unless the context indicates a different meaning. Where technical words are not defined, or where questions of interpretation arise regarding acoustical terminology, the American National Standard Institute (ANSI) definitions shall be used as a guide.
ANSI - the American National Standard Institute or its successor bodies.
Construction - any site preparation, excavation, assembly, erection, substantial repair, alteration, or similar action (excluding demolition) of public or private rights-of-way, structures, utilities, or similar property.
Daytime - the hours from 7:00 a.m. to 9:00 p.m.
dB(A) - (A-weighted sound level) - a measure of sound pressure level, in decibels, obtained from a sound-level meter using the A-weighting network or filter as specified in ANSI S1.4-1971 or the latest approved revision of that standard.
Decibel - (1/10 of a bel) - a unit (abbreviated "dB") for measuring the magnitude of sound equal to twenty (20) times the logarithm, to the base ten (10), of the ratio of the sound pressure being measured to a reference sound pressure of twenty (20) micropascals.
Emergency Generator Equipment - Generators that supply back-up power to buildings such as hospitals, hotels, and office buildings.
Emergency work - the work necessary to restore property to a safe condition following a public calamity or act of God, or the work required to protect the health and safety of persons.
Leafblowers - any portable device or machine that is gasoline or electric powered and which is designed or intended, by generating a concentrated stream of air to blow, dispel, or make airborne, leaves, grass cuttings, paper, trash, or any other type of unattached debris or material. The term includes those devices or machines that accept vacuum attachments. (D.C. Law 9-135)
Leg - (Equivalent A-Weighted Sound Level) - the constant sound level that, in a given time period, would convey the same sound energy as the actual, time varying, A-weighted sound. The number in parenthesis immediately following the term "Leg" shall denote the time period in hours.
Maximum sound level - the highest level observed on a sound level meter.
Mayor - the Mayor of the District of Columbia or his or her designated agent.
Motorcycle - any motor vehicle other than a motorized bicycle having either a tandem arrangement of two (2) wheels or a tricycle arrangement of three (3) wheels, and having a seat or saddle for the use of the operator.
Motor vehicle - any vehicle propelled either by an internal combustion engine or by electricity or steam. This term does not include motor boats and traction engines used exclusively for drawing vehicles in fields, road rollers, and vehicles propelled only upon rails and tracks.
Motorized bicycle - any motor vehicle having the following:
Nighttime - the hours from 9:00 p.m. to 7:00 a.m.
Noise - this term shall have the same definition as "sound," in the Act.
Noise disturbance - any sound which is loud and raucous or loud and unseemly and unreasonably disturbs the peace and quiet of a reasonable person of ordinary sensibilities in the vicinity thereof, unless the making and continuing of the noise is necessary for the protection or preservation of the health, safety, life, or limb of some person. In making a determination of a noise disturbance, the Mayor shall consider the location, the time of day when the noise is occurring or will occur, the duration of the noise. In addition, the Mayor may consider the magnitude of the noise relative to the maximum sound levels permitted under this act, the possible obstruction or interference with vehicular or pedestrian traffic, the number of people that are or would be affected, and such other factors as are reasonably related to the impact of the noise on the health, safety, welfare, peace, and quiet of the community. A noise shall not be considered a noise disturbance if it is made during noncommercial public speaking during the daytime and does not exceed 80 decibels inside the nearest occupied residence in districts zoned R-1A, R-1B, R-2, R-3, or R-4. Except as it may otherwise conflict with provisions of this act, all measurements of noise levels shall be performed and verified by qualified inspectors of the Department of Consumer and Regulatory Affairs in accordance with the requirements specified in Chapter 29 of Title 20 of the District of Columbia Municipal Regulations. If the noise is made at night or does not involve noncommercial public speaking, the Mayor shall not be required to measure the decibel level of the noise to find a noise disturbance.
Noise level - this term shall have the same definition as "sound level."
Noise zones - shall be defined according to the following three (3) categories, as shown, defined, and bounded on the zoning map:
Person - an individual, partnership, corporation, trust, association, firm, organization, government, or other entity.
Pre-existing source - any noise source either established and in operation or under construction prior to May 15, 1978.
Real property boundary - an imaginary line along the ground surface and its vertical extension, which separates the real property owned by one (1) person from that owned by another.
Sound - an oscillation in pressure, particle displacement, particle velocity, or other physical parameter, in a medium with internal forces that causes compression and rarefaction of that medium. The description of sound may include any characteristic of the sound, including duration, intensity, and frequency.
Sound level - the weighted sound pressure level obtained by the use of a sound level meter and frequency weighing network, such as A, B, or C as specified in the ANSI specifications for sound level meters (ANSI S1.4-1971, or the latest approved revision of ANSI S1.4 standard). If the frequency weighing employed is not indicated, the A-weighing shall apply.
Sound-level meter - an instrument to measure the sound pressure level meeting at least either the Type II requirements of the ANSI S1.4-1971 standard or the latest approved version of the ANSI S1.4 standard.
Street or highway - any road, street, alley, or way in the District of Columbia, open to the use of the public, as a matter of right, for the purposes of vehicular traffic.
Weekday - any day except Sunday or a legal holiday.
Zoning regulations - the D.C. Zoning Regulations, effective May 12, 1958, as amended (DCMR Title 11).
D.C. Mun. Regs. Tit. 20, § 2799