Denver, Colorado

as of 2001
Chapter 36  NOISE CONTROL*
*Cross reference(s)--Barking dogs, § 8-46; health and sanitation, Ch. 24; nuisances generally, Ch. 37; mufflers and prevention of noise on motor vehicles, § 54-74; loud sirens, whistles, etc., prohibited on bicycles, § 54-579.
State law reference(s)--Noise abatement, C.R.S. 1973, 25-12-101 et seq.
Sec. 36-1.  Purpose.

This chapter is enacted to protect, preserve and promote the health, safety, welfare, peace and quiet for the citizens of the city through the reduction, control and prevention of noise. It is the intent of this chapter to establish standards that will eliminate and reduce unnecessary and excessive motor vehicle and community noise, which are physically harmful and otherwise detrimental to individuals and the community in the enjoyment of life, property and conduct of business.

(Code 1950, § 717.1; Ord. No. 237-99, § 1, 3-29-99)
Sec. 36-2.  Definitions.

The following words and phrases, when used in this chapter, shall have the meanings respectively ascribed to them:

(1)     Ambient sound level shall mean the A-weighted sound level of all sound associated with a given environment, exceeded ninety (90) percent of the time (L90) measured and being a composite of sounds from many sources during the period of observation while the sound from the noise source of interest is not present.

(2)     A-weighted sound pressure level shall mean the sound pressure level as measured with a sound level meter using the A-weighting network. The standard notation is dB(A).

(3)     Commercial power equipment shall mean any equipment or device rated at more than five (5) horsepower and used for building repairs or property maintenance excluding snow removal equipment.

(4)     Commercial premises shall mean any land parcel with buildings where the use of less than fifty (50) percent of the gross floor area meets the definition of residential premises as contained in subsection (21).

(5)     Construction equipment shall mean any device or mechanical apparatus operated by fuel, electric, or pneumatic power in the excavation, construction, repair, or demolition of any building, structure, land parcel, street, alley, waterway, or appurtenance thereto.

(6)     Decibel shall mean a logarithmic unit of measure often used in measuring magnitudes of sound. The symbol is dB.

(7)     Domestic power equipment shall mean any equipment or device rated at five (5) horsepower or less and used for building repairs or grounds maintenance excluding snow removal equipment.

(8)     Emergency vehicle shall mean an authorized motor vehicle that has sound warning devices such as whistles, sirens and bells which can lawfully be used when responding to an emergency, or during a police activity or which is required by state or federal regulations (i.e., reverse alarms).

(9)     Emergency work is an activity made necessary to restore property to a safe condition following a public calamity or work required to protect persons or property from exposure to imminent danger. It includes work by private or public entities for providing or restoring immediately necessary service as well as all situations deemed necessary by the city.

(10)     Emergency power generator shall mean the equipment used to generate electrical power in the event of an interruption, malfunction or failure of the electrical power supplied by the service provider.

(11)     Gross floor area: The sum of the horizontal floor areas of a building or unit of a building, including interior balconies and mezzanines, but excluding exterior balconies. All horizontal dimensions of all floors are to be measured by the exterior faces of walls of each such floor. The gross floor area computation shall exclude the following:

a.     Any floor area devoted to mechanical equipment serving the building;

b.     Any floor area used exclusively as parking space for motor vehicles; and

c.     Floor area serving as a pedestrian mall or public access way to shops and stores.

(12)     Industrial premises shall mean any premise where manufacturing, processing or fabrication of goods or products takes place.

(13)     Motor vehicle shall mean any vehicle which is self-propelled, used primarily for transporting persons or property upon public roadways and required to be licensed according to motor vehicle registration laws. The term motor vehicle shall not include: aircraft, watercraft, motor vehicles operated on private property for recreational or amusement purposes, vehicles used exclusively on stationary rails, or specialized utility vehicles normally used only on private property in the daily course of business such as forklifts, and pallet movers.

(14)     Muffler-approved type shall mean an apparatus consisting of a series of chambers, baffle plates or other mechanical devices designed for the purpose of receiving and transmitting exhaust gases and which reduce sound emanating from such an apparatus by at least twenty (20) decibels in the A-weighting network dB(A), from the nonmuffled condition.

(15)     Noise shall mean sound that is unwanted and which causes or tends to cause adverse psychological or physiological effects on human beings.

(16)     Person shall mean any person, firm, association, organization, partnership, business, trust, corporation, company, contractor, supplier, installer, user or owner, and shall include any municipal corporation, state or federal governmental agency, district, or any officer or employee thereof.

(17)     Premises shall mean any building, structure, land, utility or portion thereof, including all appurtenances, and shall also include yards, lots, courts, inner yards and real properties without buildings or improvements, owned or controlled by a person.

(18)     Property line shall mean that real or imaginary line and its vertical extension which separates real property owned or controlled by any person from contiguous real property owned or controlled by another person. The vertical and horizontal boundaries of a dwelling unit in a multi-dwelling-unit building, condominium, or townhouse complex shall not be considered property lines separating one (1) premises from another.

(19)     Public premises shall mean all real property including appurtenances thereon which is owned or controlled by any governmental entity and shall include streets, alleys, parks and waterways.

(20)     Receptor premises shall mean the premises (residential, commercial, industrial, or public) as listed in Table A which is receiving noise emitted from the source premises after crossing one (1) or more property lines.

(21)     Residential premises shall mean any premises where single or multiple dwelling units exist and shall include primary schools, churches, nursing homes and similar institutional facilities including any commercial premises where the use of more than fifty (50) percent of the gross floor area meets this definition of residential premise.

(22)     Sound shall mean an oscillation in pressure, stress, particle displacement and particle velocity which induces auditory sensation.

(23)     Sound level meter shall mean an apparatus or instrument including a microphone, amplifier, attenuator, output meter and frequency weighting networks for the measurement of sound levels. The sound level meter shall be of a design and have the characteristics of a Type 2 or better instrument as established by the American National Standards Institute, publication S1.4-1971 entitled Specification for Sound Level Meters.

(24)     Sound pressure level shall mean twenty (20) times the logarithm to the base ten (10) of the ratio of the pressure of a sound to the reference pressure of twenty (20) micronewtons per square meter (20  X  106 Newtons/meter2), and is expressed in decibels (dB).

(25)     Source premises shall mean the premises (residential, commercial, industrial, or public) as listed in Table A that is emitting noise that is crossing one (1) or more property lines and impacting the receptor premises.

(26)     Snow removal equipment shall mean any equipment used for removing snow from land or building surfaces and shall include snow plows, snow blowers, snow sweepers, and snow shovels.

(27)     Tree maintenance equipment shall mean any equipment used in trimming or removing trees only and shall not be limited to chainsaws, chippers and stump removers.

(Code 1950, § 717.2; Ord. No. 400-86, §§ 1--3, 6-30-86; Ord. No. 237-99, § 2, 3-29-99)
Cross reference(s)--Definitions and rules of construction generally, § 1-2.
Sec. 36-3.  Noise sound pressure level measurement instrumentation.

The instrumentation for determining noise sound pressure levels shall be with a sound level meter of standard design. Sound pressure level measurements shall be made with the A-weighting network.

(Code 1950, § 717.3; Ord. No. 237-99, § 3, 3-29-99)
Sec. 36-4.  Inspections.

(a)     For the purpose of determining compliance with the provisions of this chapter, the manager of environmental health and the chief of police or their authorized representatives are hereby authorized to make inspections of all noise sources and to take measurements and tests whenever necessary to determine the quantity and character of noise. If any person refuses or restricts entry and free access to any part of a premise, or refuses inspection, testing or noise measurement of any activity, device, facility, motor vehicle, or process where inspection is sought, the manager or the chief of police or their authorized representatives may seek from the county court a warrant for inspection requiring that such person permit entry and free access without interference, restriction or obstruction, at a reasonable time, for the purpose of inspecting, testing or measuring noise. The county court shall have power, jurisdiction and authority to enforce all orders issued under the provisions of this chapter.

(b)     It shall be unlawful for any person to refuse to allow or permit the manager of environmental health or the chief of police free access to any premise when they or their authorized representative is acting in compliance with a warrant for inspection and order issued by the county court.

(c)     It shall be unlawful for any person to violate the provisions of any warrant or court order requiring inspection, testing or measurement of noise or noise services.

(d)     No person shall hinder, obstruct, delay, resist, prevent in any way, interfere, or attempt to interfere with any authorized person while in the performance of their duties under this chapter.

(Code 1950, § 717.4; Ord. No. 1110-96, § 1, 12-16-96)
Sec. 36-5.  Misrepresentation to avoid compliance.

It shall be unlawful for any person to misrepresent or give any false or inaccurate information or in any way attempt to deceive the manager of environmental health or the chief of police in order to avoid compliance with the provisions of this chapter.

(Code 1950, § 717.5-2; Ord. No. 1110-96, § 1, 12-16-96)
Sec. 36-6.  Restrictions and measurements of noise between source and receiving premises (Table A).

(a)     It shall be unlawful for any person to emit or cause to be emitted any noise which leaves the premises on which it originates, crosses a property line, and enters onto any other premises in excess of the sound pressure levels during the time periods as specified in Table A. It is further unlawful for any person to emit or cause to be emitted any noise within the public premises in excess of the limits defined in Table A.

(1)     The noise source shall be measured at any point along the property line or within the property line of the receiving premises to determine compliance with this chapter.

(2)     When it is determined that the ambient sound level at the receiving premises equals or exceeds the maximum allowable sound pressure level specified in Table A, then the ambient sound level is the standard which cannot be exceeded by the source.

Table A: Allowable Noise Levels (in dBA) with Time of Day Allowance
Receptor Premises
Residential Commercial Industrial Public
Source Premises 7am-10pm 10pm-7am 7am-10pm 10pm-7am 7am-10pm 10pm-7am 7am-10pm 10pm-7am
Residential 55 50 65 60 80 75 75 70
Commercial 55 50 65 60 80 75 75 70
- [60] [60] - - - - - -
Industrial 55 50 65 60 80 75 75 70
- [65] [65] - - - - - -
Public 55 50 65 60 80 75 75 70
- [60] [60] - - - - - -
[60] The numbers in brackets are the allowable limits that comply with exemption 14.

(12)     Any power generator providing emergency electrical power at any hospital, health clinic, nursing home or similar facilities where the loss of electrical power poses an immediate risk to the health, safety or welfare of any person, or at any premises where such equipment is required by the Denver Fire Department. Additionally, the noise emitted during the routine testing of emergency electrical power generators shall not exceed eighty-eight (88) dB(A) at a distance of twenty-five (25) feet. Routine testing shall not exceed one (1) hour in any one-week period, or two (2) hours in any six-week period and shall be confined to the hours of 10:00 a.m. to 4:00 p.m. or as otherwise approved.

(13)     Any industrial, commercial, or public premises exceeding the standards of Table A at a receiving residential premises when the zoning of the receiving residential premises does not allow residential use (residential use is nonconforming). However, in such a situation, the noise emitted by the industrial, commercial, or public premises shall not exceed the standards for receiving industrial premises.

(14)     Any industrial, commercial, or public premises exceeding the standards of Table A at a receiving residential premises when such industrial, commercial, or public premises and their emitted noise level were in existence prior to the existence of the residential premises, provided however that the existing industrial premises does not exceed sixty-five (65) dB(A) and the commercial premises do not exceed sixty (60) dB(A) when measured at the receiving residential premises.

(15)     Any noise source in existence prior to the effective date of this ordinance revision that had previously been determined to be in violation of the noise standards of Table A of Chapter 36 and has since complied and remains in compliance.

(Code 1950, § 717.6; Ord. No. 15-90, § 1, 1-8-90; Ord. No. 237-99, § 4, 3-29-99)
Sec. 36-7.  Prohibited noise activities.

The following activities are prohibited notwithstanding the sound pressure levels permitted pursuant to sections 36-6 and 36-8:

(1)     Vehicle horns. No person shall, at any time, sound any horn or other audible signal device of a motor vehicle unless it is necessary as a warning to prevent or avoid a traffic accident or reasonably inform or warn of a vehicle presence.

(2)     Trash compacting and collection. No person shall operate any trash compacting mechanism on any motor vehicle or on any premises, nor shall any person engage in any trash, rubbish or garbage collection activity between the hours of 10:00 p.m. and 7:00 a.m., when such compacting or collection activity takes place on any premises adjacent to, or across the street or alley from a residential premises.

(3)     Construction equipment and activities. No person shall operate any construction equipment nor conduct any construction activities between the hours of 9:00 p.m. and 7:00 a.m. that exceeds the noise limits of Table A; provided, however, that the board of environmental health may grant variances from the construction restrictions if it can be demonstrated that a construction project will interfere with traffic if completed during daytime hours.

(Code 1950, § 717.7; Ord. No. 237-99, § 5, 3-29-99)
Sec. 36-8.  Motor vehicle noise.

(a)     No person shall operate nor shall the owner permit the operation of any motor vehicle or combination of motor vehicles at any time or place when such operation exceeds the following noise sound pressure levels for the category of motor vehicle and for the designated time period as specified in Table B. The standards in Table B shall apply to all noise emitted from motor vehicles including any and all equipment thereon, under any condition of acceleration, deceleration, idle, grade or load and whether or not in motion.

Maximum Allowable Noise Sound Pressure Levels for Motor Vehicles
Type of Vehicle Time Period Maximum Allowable Sound Pressure Level Measurement Distance from Motor Vehicle
Motor vehicles weighing less than 10,000 pounds, manufacturers gross vehicle weight At any time 80 dB(A) 25 feet


(b)     It shall be unlawful for any person to drive or move, or for the owner of any motor vehicle to permit to be driven or moved any motor vehicle or combination of motor vehicles at any time, which is not equipped with any exhaust muffler approved by this chapter.

(c)     It shall be unlawful for any person or for the owner of a motor vehicle to modify or change the exhaust muffler, air intake muffler or any other sound reducing device in such a manner that the noise emitted from the motor vehicle exceeds the sound pressure levels as established in Table B of this section or, is increased above the sound pressure level of the vehicle as originally manufactured. Muffler cut-outs, by-passes or other devices which increase sound pressure levels, or change the original manufactured exhaust system of any motor vehicle shall be considered a violation of this chapter.

(Code 1950, § 717.8; Ord. No. 237-99, § 6, 3-29-99)
Cross reference(s)--Traffic regulation, Ch. 54.
State law reference(s)--Noise restrictions on the sale of new vehicles, C.R.S. 1973, 25-12-106.
Sec. 36-9.  City contracts to require chapter compliance.

Any written agreement, purchase order or contract whereby the city is committed to an expenditure of funds in return for work, labor, services, supplies, equipment, materials or any combination thereof, shall not be entered into unless such agreement, purchase order or instrument contains provisions that any equipment or activities which are subject to the provisions of this chapter will be operated, constructed, conducted or manufactured without violating the provisions of this chapter.

(Code 1950, § 717.9)
Cross reference(s)--Contracts, purchases and conveyances generally, § 20-51 et seq.
Sec. 36-10.  Other applicable provisions.

(a)     Loud, persistent, or habitual dog barking, howling or yelping shall be controlled and enforced as provided in Chapter 8, Article II, Division 3, provided however that dog barking noise emitted from licensed commercial dog kennels shall also be subject to the provisions of section 36-6.

(b)     Loud or disturbing noise emitted by human voices shall be enforced pursuant to the provisions of Chapter 38, Article IV of this Code.

(Code 1950, § 717.10; Ord. No. 237-99, § 7, 3-29-99)