DCMR Title 20 (Environment) - Present file contents:

Chapter 28 (Maximum Noise Levels) and Chapter 29 (Noise Measuring Test Procedures)

CHAPTER 28 MAXIMUM NOISE LEVELS
Secs.
2800 Musical Instruments, Loudspeakers Amplifiers, and Unamplified Voices
2801 Mechanical Equipment
2802 Construction
2803 Construction in Residential Zones
2804 Explosives
2805 Hawkers, Peddlers, and Vendors
2806 Trash Collection in and Adjacent to Residential Zones
2807 Vehicle-Mounted Loud Speakers
2808 Leaf Blowers
2809 [Reserved]
2810 New Motor Vehicles
2811 Operational Limits for Motor Vehicles
2812 Alteration of Motor Vehicle Exhaust System
2813 Motor Vehicle Inspection
2899 Definitions

2800 MUSICAL INSTRUMENTS, LOUDSPEAKERS, AMPLIFIERS, AND UNAMPLIFIED VOICES
2800.1Noise resulting from the musical instruments, loudspeakers, amplifiers, and unamplified voices shall not exceed the maximum noise levels contained in this section.
2800.2It shall be unlawful for any person to make, continue, or cause to be made or continued any noise disturbance by the operation, use, or playing of any musical instrument or device, loud speaker, sound amplifier, or other similar device, unamplified voice, for the production or reproduction of sound on private property or public space.
2800.3Parades and public gatherings conducted pursuant to a permit issued by the Metropolitan Police Department (as provided for in 24 DCMR, Chapter 7) shall be exempt from the noise disturbance limitation.
2800.4Sounds shall not project outside a place of business at a level that exceeds sixty (60) dB(A) at a distance of not less than one (1) meter from outside the business establishment. Nothing in the Act shall be construed to prohibit the use of musical instruments, amplifiers, or stereo equipment for the sole enjoyment of the listener; Provided, that the sound does not exceed sixty (60) dB(A) or the applicable noise level for the zone from which the sound emanates at a distance of one (1) meter from the source.
2800.5It shall be unlawful for any person to make, continue or cause to be made or continued any noise disturbance as that term is defined in 20 DCMR §2799 created by the operation or use of a loud speaker, sound amplifier. radio, Or musical instrument on public streets, alleys, or thoroughfares in the District of Columbia. Public assembly activities provided for in 20 DCMR §2500.3 and non-commercial public speaking are exempt from the limitations set forth in this section.
AUTHORITY: Unless otherwise noted. the authority for this chapters An Act approved January 26, 1887 24 Slat. 368, ch. 49. as amended: D.C. Code §1.315 11992 RepI. Vol.1: the §§422(6) and 422(11) of the District Columbia Self-Government and Governmental Reorganization Act; the District of Columbia Noise Control Act of 1977 D.C Law 2.53, as amended: Mayor's Order 79-28 dated February 5,1979.
EDITOR'S NOTE: Chapter 31 Maximum Noise Levels was renumbered Chapter 28.
SOURCE: Section 5 of the District of Columbia None Control Act of 1977 DC. Law 2-53, 24 DCR 5293, 5308 December 30, 1977) as amended by §4 of the D.C Noise Control Act of 1977 Amendment Act of 1986. D.C. Law 6-180, 33 DCR 7660, 7661 (December 21 1986) and by §2 of the Noise Control Amendment Act of 1996, DC. Law 11-161, 43 DCR 3727, 3729 (July 19, 1996).

2801 MECHANICAL EQUIPMENT
2801.1Noise resulting from mechanical equipment shall not exceed the maximum noise levels contained in this section.
2801.2Noise resulting from the use or operation of any air-conditioning, refrigerator, heat pump, fan, swimming pool equipment, or other mechanical equipment, regardless of location, shall be prohibited in excess of sixty (601 (IB(A) when measured at the property line or as close to the property line as practical if there is an obstruction.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977 DC Law 2-53, 24 DCR 6293, 5309 (December 30, 1977)

2802 CONSTRUCTION
2802.1From 7:00 am. to 7:00 p.m. on any weekday, noise levels resulting from construction or demolition (excluding pile driver devices) shall not exceed a Leq(1) of eighty (50) dB(A) unless granted a variance under §2705 of Chapter 27 of this subtitle.
2802.2From 7:00 p.m. to 7:00 am. the maximum noise levels prescribed in §2701 of Chapter 27 of this title shall apply.
2802.3In cases involving noise from construction or demolition, measurements shall be made twenty-five feet (25 ft.) from the outermost limits of the construction site.
2802.4No permit for building construction or demolition shall be issued until the permit applicant has assured in writing that the noise emanating from the planned construction will comply with the limitations established by this section.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977, D.C Law 2-53, 24 DCR 5293, 5308 (December 39, 1977).

2803 CONSTRUCTION IN RESIDENTIAL ZONES
2803.1Noise emanating from construction in residential zones shall be prohibited during the hours specified in this section irrespective of its compliance with §2701 of Chapter 27 of this subtitle.
2803.2No noise from construction, excluding minor home repairs, shall be permitted within a residential, special purpose, or waterfront zone on any Sunday or legal holiday, or after 7:00 p.m. and before 7:00 a.m. on any weekday.
2803.3The limitation of §2803.2 shall not apply to the following:
  1. Portable power tools used for minor improvement of real and personal residential property otherwise allowable under this section;
  2. Work performed by public utilities as defined in the Act approved March 4,1913 (37 Stat. 974; D.C. Code §43-103 (1990 RepI. Vol.));
  3. Work performed by the Washington Metropolitan Area Transit Authority as defined in D.C. Code §§1-1410 et seq. (i992 RepI. Vol.): or
  4. Work performed by the subcontractors of public utilities and the Washington Metropolitan Area Transit Authority as provided in §§2503.3(b) and 2803.3(c).
2803.4Noise emanating from the sources exempted in §2803.3 shall comply with the maximum noise levels prescribed in §2701 of Chapter 27 of this subtitle.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977, D.C. Law 2-53, 24 DCR 5293, 5209 December 30, 1977).

2804 EXPLOSIVES
2804.1Noise emanating from explosives shall be prohibited during the hours specified in this section irrespective of its compliance with §2701 of Chapter 27 of this subtitle.
2804.2No blasting with explosives shall be performed on any Sunday or legal holiday or at nighttime on weekdays, except by special permit as provided in §1301 of the Second Amendment to the 1972 Building Code of the District of Columbia (Title 12 DCMR).
EDITOR'S NOTE: The Building code referred to in this title has been superseded by DC. Law 6-216. Construction Codes Approval and Amendments Act of 1986, effective March 21, 1987. The construction regulations existing prior to March 21. 1987, remain in effect for projects having reached specified stages of completion. D.C. Law 6-216 adopted the 1984 National SOCA Codes, and the 1985 D.C. Supplement to the National BOCA Codes. Effective November27. 1992 139 DCR 86651, the 1984 BOCA Codes. and the 1985 D.C. Supplement to the National BOCA Codes were superseded by the adoption of the 1990 BOCA Codes, and the 1992 D.C. Supplement to the BOCA Codes.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977. D.C. Law 2-53. 24 DCR 5293. 5310 December 30. 1977).

2805 HAWKERS, PEDDLERS, AND VENDORS
2805.1The shouting and crying of hawkers, peddlers, and vendors shall be prohibited at nighttime on any day of the week, irrespective of its compliance with §2701 of Chapter 27 of this subtitle.
2805.2The limitation of §2805.1 shall not be construed to prohibit selling by outcry of merchandise, food, and beverages at licensed sporting events, parades, fairs, circuses, or other similar licensed entertainment events.
SOURCE: Section 5 of tie District of Columbia Noise Control Act of 1977, DC Law 2-53, 24 DCR 5293, 5309 (December 30, 1977).

2806 TRASH COLLECTION IN AND ADJACENT TO RESIDENTIAL ZONES
2806.1Noise emanating from trash collection in any residential, special purpose. or waterfront zone shall be prohibited luring the hours specified in this section irrespective of its compliance with §2701 of this subtitle.
2806.2No person shall operate or permit the operation of any refuse collection vehicle in or within three hundred feet (300 ft.) of any residential, special purpose, or waterfront zone at nighttime on any (lay of the week. This prohibition shall not apply to vehicles owned by the District government employed for emptying litter receptacles.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977, D.C. Law 2-53, 24 DCR 5293, 5311 (December 30. 1977) as amended by §2 of the Noise Control Amendment Regulation Act of 185, DC Law 6-93, 33 DCR 314 (January 17, 1986).

2807 VEHICLE-MOUNTED LOUD SPEAKERS
2807.1Noise emanating from vehicle-mounted sound amplifying equipment, instruments, and transmitting devices shall be prohibited during the hours specified in this section irrespective of its compliance with §2701 of Chapter 27 of this subtitle.
2807.2Vehicle-mounted sound amplifying equipment, instruments, and transmitting devices shall be prohibited in streets or on highways after 9:00 am., and between 4:00 p.m. and 6:30 p.m.
2807.3Vehicle-mounted sound amplifying equipment, instruments, and transmitting devices shall be prohibited in streets or on highways after 9:00 p.m. and before 9:30 am. During all other hours their use shall be subject to the limitations of the noise disturbance standards, and the following conditions:
  1. The vehicles are required, where traffic conditions permit, to move at least five miles per hour (5 mph);
  2. When the vehicles are stopped for any cause, no sound shall be amplified or transmitted for more than one (1) minute. so long as the vehicle remains stationary:
  3. Operators of the vehicles shall not hold sound amplifying equipment, instruments, or transmitting devices by hand while the vehicles are in operation; and
  4. When vehicles are parked in legal off-street locations, the conditions set forth in §2807 of this chapter shall not apply.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977 D.C. Law 2-53, 24 DCR 5293, 5311 (December 30, 1977), as amended by §2 of the Noise Control Amendment Act of 1998, D.C. Law 11-181, 42 DCR 3727, 3729 (July 19, 1996).

2808 LEAF BLOWERS
2808.1Except as provided under §2808.2, no person shall sell, offer for sale, or use, at any time, a leaf blower in the District of Columbia that has an average sound level exceeding seventy (70) dB(A) at a distance of fifty feet (50 ft.) from the leaf blower as measured in accordance with §2808.5 of this section. A leaf blower shall not be used at nighttime, between the hours of 8:30 p.m. and 8:00 am. in the District of Columbia.
2808.2Upon the effective date of the District of Columbia Noise Control Amendment Act of 1992 ("1992 Act"), a person who sells, at retail, a leaf blower in the District of Columbia that exceeds the maximum sound level established in §2808.1 of this section must provide conspicuous notice to the consumer that the leaf blower may not be used in the District.
2808.3A person who purchased a leaf blower prior to the effective date of the 1992 act. or who can demonstrate that the leaf blower was manufactured prior to the effective date of the 1992 Act, may use that leaf blower for the next five ~5) years. even though its average sound level exceeds the standard established in §2808.1 of this section, if its use is otherwise permitted by the Act.
2808.4In addition to any other enforcement measure authorized under this act, the Mayor may inspect and, upon request, require a person to produce any leaf blower that is sold, offered for sale, or used. in order to determine compliance with this act. The Mayor shall use, to the extent possible, a manufacturers written sound level representations, design and use specifications, and approximate manufacture date, as appropriate, as aids to determine compliance. A person who in good faith relies on a manufacturers written sound level representation is not subject to penalties under § 13 for violation of the Act.
2808.5Compliance with sound level requirements of this act shall be determined in accordance with a sound measurement testing standard for leaf blowers that has been deemed by the Mayor to be acceptable and adopted by regulation.
SOURCE: Section 2 of the District of Columbia Noise Control Amendment Act of 1992, D.C. Law 9-135, 39 DCR 4079 (June 12, 1992) 2809 [RESERVED]

2810 NEW MOTOR VEHICLES
2810.1No person shall either sell or offer for sale a new motor vehicle or motorcycle that is to be registered for use upon the public highway that exceeds the maximum noise limits designated in the table of §2810.2 when measured at a distance of fifty feet (50 ft.) from the center line of travel in accordance with test procedures (as may be appropriate for the vehicle being tested) as prescribed in this subsection:
  1. Those described by the Society of Automotive Engineers, Inc. (SAE), including SAE Standard J986(a) (for vehicles ten thousand (10,000) GVWR and under), SAE Standard J3 (for motorcycles), and SAE Standard J184 (for vehicles over ten thousand (10,000) GVWR);
  2. Those recommended by Practice J184 (for qualifying a sound data acquisition system), and subsequent revisions of the standard: or
  3. A nationally-recognized test procedure, such as those promulgated by the EPA, as the administering agency may prescribe in accordance with §§2700.7 through 2700.9 of Chapter 27 of this subtitle.
2810.2Each manufacturer, distributor, or importer, or his or her designated agent, shall certify in writing to the Mayor that all motor vehicles or motorcycles sold by him or her in the District comply with the provisions of the following table:
TYPE OF VEHICLE AND DATE OF MANUFACTUREMAXIMUM NOISE LEVEL
Any motorcycle, other than a motorized bicycle, manufactured after 197683 dB(A)
Any motor vehicle with a gross vehicle rating of more than ten thousand pounds (10.000 lbs.) manufactured on or after January 1. 197883 dB(A)
Any motor vehicle with a gross vehicle weight rating of more than ten thousand pounds (10.000 lbs.) manufactured on or after January 1. 1982 80 dB(A)
Any other motor vehicle weighing ten thousand pounds (10.000 lbs.) or less manufactured on or after January 1. 197683 dB(A)
Any other motor vehicle weighing ten thousand pounds (10,000 lbs.) or less manufactured after January 1,197880 dB(A)
SOURCE: Section 6 of the District of Columbia Noise Control Act of 1977, D.C. Law 2-53, 24 DCR 5293, 5312 (December 30, 1977).

2811 OPERATIONAL LIMITS FOR MOTOR VEHICLES
2811.1No person shall operate a motorcycle, motor vehicle, or combination of motor vehicles of a type subject to registration under D.C. Code §40-103 (1990 RepI. Vol.) at any time, or under any condition of grade, load, acceleration, or deceleration in a manner that exceeds the maximum noise limits designated in the table of this subsection for the specified speed limits, measured at a distance of fifty feet (50 ft.) from the center line of travel by a sound level meter switched to the A-weighting network, in accordance with such nationally recognized test procedures as the administering agency may prescribe in accordance with §§2700.7 through 2700.9 of Chapter 27 of this subtitle.
TYPE OF VEHICLENOISE LIMIT
35 MPH or lessOver 35 MPHStationary Run-up
Any motor vehicle with a manufacturer's gross vehicle weight rating of ten thousand pounds (10.000 lbs.) or more, and any combination of vehicles towed by that motor vehicle86 dB(A)90 dB(A)88 dB(a)
Any motorcycle82 dB(A)86 dB(A)-
Any other motor vehicle and any combination of vehicles towed by a motor vehicle with a manufactures gross weight rating of ten thousand pounds (10,000 lbs.) or more76 dB(A)82 dB(A)-
2811.2Where a test procedure is used for which the noise levels prescribed in the table in §2811.1 would not be appropriate, the administering agency may establish and publish a table with the appropriate levels which are substantially equivalent to those established in that table.
2811.3The public shall be provided with at least thirty (30) days to comment on all new standards and procedures before the standards are made final.
2811.4For the purposes of this section, a motor truck, truck tractor. or bus that is not equipped with an identification plate or marking that bears the manufacturer's gross vehicle weight shall be considered as having a rating of ten thousand pounds (10,000 lbs.) or more if the unladen weight is more than nine thousand pounds (9,000 lbs.).
2811.5No person shall operate a motor vehicle equipped with an engine speed governor that generates a sound level in excess of eighty-eight (88) dB(A) measured on an open site with a fast meter response at fifty feet (50 ft.) from the longitudinal center line of the vehicle when its engine is accelerated from idle to a wide-open throttle governed speed with the vehicle stationary, transmission in neutral, and clutch engaged.
2811.6The administering agency may by regulation prescribe correctional factors to the limits prescribed in the table of §2811.1 of this section when measurements are made at a site that contains large reflecting surfaces in close proximity to the vehicle or noise measuring microphone.
2811.7A violation of the adjusted levels as provided in §2811.6 shall constitute a violation l)f this section.
2811.8In the event that it is impractical to obtain a measurement fifty feet (50 ft.) from the center line of travel, the actual distance shall be measured and one (1) of correctional factors in the following table shall be applied to the maximum permissible sound levels prescribed in the table of §2811.1 of this section.
DISTANCECORRECTION
Soft siteHard site
35 - less than 39 ft. +3 dB(A)+5 dB(A)
39 - less than 43 ft.+2 dB(A)+4 dB(A)
43 - less than 48 ft.+1 dB(A)+3 dB(A)
48 - less than 58 ft.0 dB(A)+2 dB(A)
58 - less than 70 ft.-1 dB(A)+1 dB(A)
70 - less than 83 ft.-2 dB(A) 0 dB(A)
2811.9For the purposes of this section, "soft test site" shall mean any test site having the ground surface covered with grass, another ground cover, or a similar absorption material for one-half (1/2) or more of the distance between the microphone target point and the microphone location point.
2811.10For the purposes of this section, "hard test site" means any test site having the ground surface covered with concrete, asphalt, packed dirt, gravel, or similar reflective material for more than one-half (1/2) the distance between the microphone target point and the microphone location point.
SOURCE: Section 5 of the District of Columbia Noise Control Act of 1977, D.C Law 2-53, 24 DCR 5293, 5313 (December 30, 1977).

2812 ALTERATION OF MOTOR VEHICLE EXHAUST SYSTEM
2812.2No person shall use or operate a motor vehicle or a motorcycle having an exhaust system that has been modified or altered in a manner that will amplify or increase the noise emitted by the vehicle above the level permitted under §2811 of this chapter.
2832.1No person shall modify or alter the exhaust system of a motor vehicle or motorcycle in a manner that will amplify or increase the noise emitted by the vehicle above the level permitted under §2811 of this chapter.
SOURCE: Section 6 of the District of Columbia Noise Control Act of 1977, D.C. Law 2-53, 24 DCR 5293, 5317 (December 3D, 1977(.

2813 MOTOR VEHICLE INSPECTION
2813.1The Mayor shall conduct a study to determine the advantages and feasibility of requiring a noise inspection as a part of the annual motor vehicle inspection program.
2813.2The study required by §2813.1 shall be submitted to the Council of the District of Columbia not later than six months (6 mos.) after May 15. 1978, and shall include the following:
  1. An estimate of the cost to the District of requiring a motor vehicle inspection program for noise (computing separately the cost for District-owned motor vehicles in contrast to the cost of all vehicles):
  2. An estimate of the length of time that would be required per vehicle for the test, and the impact this would have on the total inspection program:
  3. The test procedures that would be used:
  4. An estimate of the number of cars that would fail the test, and the appropriate cost to each registrant to bring a car into compliance:
  5. The impact of the program on the repair stations in the District: and
  6. The impact of the program on noise levels in the District.
SOURCE: Section 6 of the District of Columbia Noise Control Act of 1977, DC. Law 2-53. 24 DCR 5293, 5316 (December 30. 1977(

2899 DEFINITIONS
2899.1The meanings ascribed to the definitions appearing in §2799.1 of Chapter 27 of this subtitle shall apply to the terms in this chapter.

CHAPTER 29 NOISE MEASURING TEST PROCEDURES
Secs.
2900General Provisions
2901Equipment
2902Sound Level Meter Calibration
2903Equipment Settings
2904Measurement Locations
2905Measurement Procedures
2906Data and Reports
2999Definitions

2900 GENERAL PROVISIONS
2900.1The purpose of this chapter is to establish standard testing procedures for measuring noise levels as prescribed under the provisions of Chapters 27 an(l 28 of this subtitle, the D.C. Noise Control Act of 1977 (D.C. Law 2-53, March 23,1978).
2900.2The intent of this chapter shall be to do the following:
  1. Specify straight-forward procedures that are applicable to the large majority of expected situations; and
  2. Specify the limits of applicability of those procedures such as situations in which acoustical specialists or specialized equipment may be required to supplement the procedures.
2900.3The measurement procedures provided in this chapter shall be reviewed periodically with reference to changes in the practice of noise measurement, instrumentation, District code, and legal precedent.
2900.4The measurement of noise produced by motor vehicles in transit shall be prescribed by District and federal laws. Enforcement by police officers shall be provided by District law.
2900.5Any situation in which the noise source cannot be demonstrated to increase the total noise at the measurement point by at least four (4) dB(A) over the ambient level shall be considered unmeasurable by the techniques described in this chapter.
2900.6Any situation in which readings exceed the statutory limits, but are less than the statutory limit plus the grace limit, the noise shall be measured with more specialized or more accurate equipment prior to deciding whether the source is in compliance with the Act.
2900.7When readings exceed the statutory limits, hut are less than the statutory limit plus the grace limit, consultation with qualified professional personnel shall be required.
AUTHORITY: Unless otherwise noted, the authority for this chapter is An Act approved January 28. 1887 24 Stat 368, ch. 49. as amended: DC. Code §1-315 1962 Repl. Vol.): the §§422(6) and 422(11) of the District of Columbia Self Government and Governmental Reorganization Act: the District of Columbia Noise control Act of 1977. DC Law 2-53: as amended: Mayors Order 79-28 dated February 6. 1979.
EDITOR'S NOTE: Chapter 32, Noise Measuring Test Procedures was renumbered Chapter 29.
SOURCE: Final Rulemaking published at 28 OCR 1499, 1501 1505 (September28 1979).

2901 EQUIPMENT
2901.1Sound-level meters and microphones shall meet Type II specifications per ANSI S 1.4-1971.
2901.2Each sound-level meter shall be qualified annually.
2901.3Each sound-level meter and microphone device shall meet the following specifications:
  1. External calibration devices with a known sound pressure level output at a single known frequency between two hundred (200) Hz and one thousand (1,000) Hz. as specified by the manufacturer:
  2. Windscreen with insertion loss less than five tenths (0.5) dB(A) below eight (8) kHz:
  3. Stopwatch, capable of cumulative operation and accurate to two percent (2%) or better:
  4. Wind speed indicator with at least twenty percent (20%) accuracy at twelve miles per hour (12 mph): and
  5. Earphones with impedance meeting the sound level meter manufacturer's specifications.
SOURCE: Final Rulemaking published at 26 DCR 1499, 1501 (September 28, 1979).

2902 SOUND LEVEL METER CALIBRATION
2902.1A battery check shall be performed immediately before and after a series of measurements at each test site.
2902.2An external calibration shall be made immediately before a series of measurements at each test site and, if necessary, the meter shall be adjusted to read within two tenths (0.2) dB(A) of the level specified by the calibration unit.
2902.3Measurements may be assumed to be valid if a calibration check after a series of measurements agrees to within five tenths (0.5) dB(A), otherwise measurements shall not be used.
2902.4Calibration checks also may be made immediately after the series of measurements and at least one (I) time per hour during the measurement series to ensure continuing accuracy of the equipment.
SOURCE: Final Rulemaking published at 26 DCR 1499,1501 (September 28, 1979).

2903 EQUIPMENT SETTINGS
2903.1In measuring impulsive or rapidly fluctuating noise, the following procedures shall be followed:
  1. A windscreen shall be used for all outdoor measurements;
  2. The "C" scale shall be used on the sound level meter;
  3. The attenuator shall be set so that the measured levels fall between the zero mark and the full scale mark on the meter scale; and
  4. The fast meter response shall be used on the sound level meter.
2903.2In measuring steady (including intermittent, slowly fluctuating, or quasi-steady) noise, the following procedures shall be followed:
  1. A windscreen shall be used for all outdoor measurements;
  2. The "A" scale shall be used on the sound level meter;
  3. The attenuator shall be set so that the measured levels fall between the zero mark and the full scale mark on the meter scale. At least five (5) seconds shall elapse after the attenuator is changed before measurements are taken; and
  4. The slow meter response shall be used on the sound level meter.
SOURCE: Final Rulemaking published at 26 OCR 1499. 1502 (September 28, 1979).

2904 MEASUREMENT LOCATIONS
2904.1Measurements shall be taken at the following locations:
  1. At the property line of the property on which the noise source is located. or as close as practicable if there is an obstruction:
  2. At a distance of one (1) meter from any musical instrument or device, or loud speaker, sound amplifier, or other similar machine or device for the production or reproduction of sound, with exceptions as designated in the Act:
  3. At a distance of twenty five feet (25 ft.) from the outermost limits of a construction site: and
  4. At a distance of fifty feet (50 ft.) from the center line of traffic for motor vehicles.
2904.2The microphone shall be at least three feet (3 ft.) above the surface while measurements are being taken. except for motor vehicle stationary tests which shall be determined.
2904.3The microphone orientation shall be as specified by the manufacturer.
2904.4Measurements conducted on private property shall be taken with the permission of the owner or the owners representative, or under the authority of a search warrant or a court order.
2904.5Outdoor measurements shall not be conducted in the presence of wind speeds greater than twelve miles per hour ~12 mph), nor in the presence of precipitation or fog.
SOURCE: Final Rulemaking published at 26 CCR 1499, 1502 (September 28, 1979)

2905 MEASUREMENT PROCEDURES
2905.1Unless impracticable. earphones shall be used occasionally while noise measurements are being taken as a periodic check to ensure that the meter is responding properly to the noise source being monitored.
2905.2In the case of steady (including intermittent, slowly fluctuating, or quasi-steady) noise, a measurement of the ambient noise level shall be required.
2905.3If the ambient noise level of steady noise is within ten I 10) OBA) of the source sound level, the corrections specified in the table of §2905.7 of this section shall be applied to determine the noise level due solely to the source being investigated. and the source shall be interpolated as necessary.
2905.4If the ambient level of steady noise is less than three (3) dB(A) from the noise source, no correction may be made and measurements cannot indicate true source noise level.
2905.5Before citing a violation of a noise limit which may not be exceeded regardless of duration, a two and five tenths (2.5) dB(A) grace shall be allowed to account for all possible meter inaccuracies.
2905.6Several measurements showing a violation shall be taken with at least twenty (20) seconds between each measurement.
2905.7The following table shall be used for making corrections to measured ambient sound pressure levels:
Difference (in decibels) between sound pressure level measured with sound source operating and ambient sound pressure level along dB(A) Correction (in decibels) to be subtracted from sound pressure level measures with sound source operating to obtain sound pressure level due to sound source along dB(A)
Less than 4Measurement can not be made
42.2
51.7
61.3
71.0
80.8
90.6
100.4
more than 100
SOURCE: Final Rulemaking published at26 DCR 1499. 1504 (September 28, 1979).

2906 DATA AND REPORTS
2906.1The operator shall be required to fill out all pertinent information on the noise data form for field measurements.
2906.2For each set of readings, the following information shall be required:
  1. Date, time, location, operator's name;
  2. Wind speed and direction;
  3. All instrumentation models and identifying numbers;
  4. A sketch of the site, including measurements points, noise sources, buildings, etc.;
  5. Measurement of noise peaks and steady levels to the nearest decibel, and duration;
  6. A description of special techniques employed;
  7. A description of the noise, noting especially if there is an apparent pure tone or impulsive content;
  8. The meter damping used (fast or slow); and
  9. Measurement of ambient and description of ambient if obvious (highway, dogs. etc.).
2906.3If the ambient level is four to ten (4-10) dB(A) below the level found with the source operating, corrections shall be made to obtain the source noise level. The corrections shall be shown.
SOURCE: Final Rulemaking published at 26 DCR 1099. 1504 (September 28, 1979).

2999 DEFINITIONS
2999.1The meanings ascribed to the definitions appearing in §2799.1 of Chapter 27 of this subtitle shall apply to the terms in this chapter.
2999.2In addition to the definitions cited in Chapter 27, the following words shall have the meaning ascribed:
Ambient - the noise remaining when the source being measured is turned off.
Calibration, external - the testing under controlled conditions of the sound level monitoring system, by use of a calibration device, whose input sound pressure level and frequency are accurately known, for the purpose of ascertaining the accuracy of the system at the input level and frequency within the meaning of the Act. The system includes a microphone. microphone cable, and sound level meter and its internal components.
Descriptors, acoustical - the following descriptors are often used:
dB(A) - A-weighted sound level measured in decibels;
Ld - daytime equivalent A-weighted sound level between the hours of 0700 and 2100;
Lin - day-night average sound level; the twenty-four hour (24) weighted equivalent sound level, with a ten (10) decibel penalty applied to nighttime levels;
Leq - equivalent A-weighted sound level over a given period of time;
Leq(1) - the Leq(1) is used in measuring construction noise and is the value of a steady state sound which has the same A-weighted average sound energy as that contained in a time varying sound. In this case, it is the equivalent sound level measured over a one (1) hour period. It is measured best with a statistical noise analyzer:
Ln - nighttime equivalent A-weighted sound level between the hours of 0700 and 2100:
Lmax - maximum A-weighted sound level for a given time interval or event: and
Lx - x percent sound level, the A-weighted sound level equaled or exceeded x% of time. For example: L10: sound level exceeded ten (10%) percent of time (usually the loudest level): L50: sound level exceeded fifty percent (50%) of time; and L90: sound level exceeded ninety percent (90%) of the time (usually the quietest level).
External Calibration - the testing under controlled conditions of the sound level monitoring system, by use of a calibration device, whose input sound pressure level and frequency are accurately known for the purpose of ascertaining the accuracy of the system at the input level and frequency within the meaning of the Act. The system includes a microphone. microphone cable, sound level meter and its internal Components).
Intermittent noise - a noise that goes on and off but that is steady while it is on.
Large reflecting surface - a surface that may cause an interference with the noise measurements being taken (a wall, for example).
Pure tone - a single frequency that predominates to the extent that it is audible. Pure tones are characterized by the following: a hum, moan, howl, whine, or whistle. depending on their frequency.
Qualified - calibrated by an authorized acoustical standards laboratory or an authorized factory representative.
Quasi-steady noise - a rapid series of impulses that has the same effect on the sound level meter as a steady noise.
Qualification - a comprehensive series of tests (including calibration using the full frequency response of a microphone, plus meter, plus A-weighted network) demonstrating compliance with ANSI specifications in addition to, but not required, calibration within the meaning of the Act.
Rapidly fluctuating - continuous noise whose level varies rapidly over a range greater than three (3) dB(A) read on the fast scale during the course of the measurements.
Slowly fluctuating - continuous noise whose level varies slowly over a range greater than three (3) dB(A) read on the slow scale during the course of the measurements.
Steady noise - a noise whose level varies less than three (3) dB(A) read on the slow scale during the course of the measurements.
Source of violation - consists of a single source, or of several distinct sources if all are being operated on the property from which the noise originates.
SOURCE: Final Rulemaking published at 26 DCR 1499 (September 28, 1979).