OLR Research Report

October 6, 2003




By: Paul Frisman, Associate Analyst

You asked if motorcycle noise standards are different than those for cars and if so, why. You wanted to know how the standards are enforced, and whether the federal government also regulates motorcycle noise.


By state regulation, motorcycles manufactured in or after 1979 cannot exceed a noise level of 84 decibels (dB) when traveling more than 35 mph on a paved street or highway. This is noisier than the maximum noise levels allowed for cars, but less noisy than the permissible noise levels for buses and other vehicles weighing more than 10,000 pounds. We could not determine from the Department of Motor Vehicles (DMV) or from the regulation’s history why DMV chose this particular standard. However, DMV may have used reasoning similar to that later used by the U. S. Environmental Protection Agency (EPA) when it set federal standards for motorcycle noise. EPA weighed the public benefit of less noise against the cost to motorcycle manufacturers of reducing motorcycle noise levels.

State and local law enforcement officers enforce state noise laws and municipal noise ordinances. Enforcement is difficult, however, because of demands on police personnel, the need to use sophisticated testing equipment, and the transitory nature of the offense. (By the time police respond to a complaint, the offender — and the noise — are usually long

gone. ) During FY 2002-03, just over 2,100 motor vehicle noise-related cases were disposed of. More than one-third of these cases were dismissed or resulted in not guilty verdicts. Please see OLR Report 94-R-0827 for more information.

The EPA has enacted limits on motorcycle noise that apply to motorcycle manufacturers and makers of aftermarket parts and equipment, whose products are installed after purchase.


State law requires the DMV commissioner to adopt regulations, with the advice of the Department of Environmental Protection, that establish maximum permissible noise levels for all motor vehicles, including motorcycles. The law prohibits anyone from operating any vehicle at any time or under any condition in a manner that exceeds the maximum decibel level established for the vehicle. It also prohibits an owner from allowing his vehicle to be operated in violation of these maximum noise levels. Additionally, no one may sell or offer a new vehicle for sale if it produces a maximum noise level that exceeds the level established in the regulations (CGS 14-80a(a) and 80a(b)).

The law also authorizes the DMV commissioner to establish a procedure for checking maximum noise levels of vehicles. The noise level must be measured 50 feet from the centerline of the vehicle. If the test procedure provides for measuring the noise from closer than 50 feet from the vehicle, the measuring devices must be calibrated in a way that creates an equivalency to measuring the sound at a distance of 50 feet.

The DMV regulations establish a specific maximum permissible decibel level for motorcycles for several types of operating conditions (see Table 1, below).

Defective/Improper Mufflers

State law also requires all motor vehicles to be "operated, equipped, constructed and adjusted to prevent unnecessary or unusual noise. " It requires that vehicles with internal combustion engines be equipped with a muffler designed to prevent excessive, unusual, or unnecessary noise. The muffler must be "maintained by the owner in good working order and shall be in use whenever the motor vehicle is operated. " The law prohibits anyone, including a motorcycle dealer, from installing, and prohibits anyone from using, a muffler that lacks interior baffle plates or other effective muffling devices, a gutted muffler, a muffler cutout, or a straight exhaust, except in permitted racing events or exhibitions. Also, the law prohibits the use of any mechanical device that amplifies vehicle noise. The law prohibits anyone, including a repairer or motorcycle dealer, from removing all or part of a muffler except to repair or replace it to more effectively prevent noise. Finally, it prohibits anyone from using any extension or device on the exhaust system or tail pipe that will cause excessive or unusual noise (CGS 14-80(a) and 80(b)).

Change in Penalty

The fine for violating the law on maximum noise levels for motor vehicles or the use of defective or improper mufflers is $ 150 (PA 03-180).


A decibel (dB) is the basic measurement unit for sound. Decibel measurements are made on a logarithmic scale, which means that an increase of 10 decibels approximates a perceived doubling of the noise level. A noise source measuring 70 dB is therefore 10 times louder than a source measuring 60 dB and 100 times louder than a source reading 50 dB. The average background noise in a typical home is between 40 and 50 dB. State and federal motor vehicle regulations use the “dBA” scale of measurement, which is the scale that most closely approximates the sensitivity of the human ear.


The maximum permissible noise level for a motorcycle manufactured on or after January 1, 1979 ranges from 78 dB to 84 dB, depending on the motorcycle’s speed and the road surface on which it travels. This is louder than the maximum permissible noise level for passenger cars manufactured during the same period (72 dB to 81 dB), but quieter than the maximum permissible noise levels for buses (83 to 90 dB), and vehicles weighing more than 10,000 pounds (86 to 92 dB) (Conn. Agencies Regs. 14-80-1 et seq. ). (Note: these levels refer to highway operation. Different levels apply to vehicles manufactured before January 1, 1979, and to stationary vehicles. ) Table 1 lists the noise levels for different highway and road surfaces and for stationary operation.

Table 1: Maximum Permissible Noise Levels for Certain Motor Vehicles manufactured after January 1, 1979


Highway Operation, soft site,*

35 mph or less

Highway Operation, soft site, above 35 mph

Highway Operation, hard site,*

35 mph or less

Highway Operation, hard site, above 35 mph

Stationary Operation,

soft site

Stationary Operation, hard site


78 dB

82 dB

80 dB

84 dB

78 dB

80 dB

Passenger Cars, less than 10,000 pounds

72 dB

79 dB

74 dB

81 dB

72 dB

74 dB


83 dB

88 dB

86 dB

90 dB

83 dB

85 dB

Vehicles more than 10,000 pounds

86 dB

90 dB

88 dB

92 dB

86 dB

88 dB

Source: Conn. Agencies Regs. 14-80a-4a

* Soft site includes surfaces covered with grass or other ground cover; hard site includes concrete, asphalt, packed dirt, and gravel surfaces.

Reasons for Different Standards

The standards took effect June 1, 1978. We could not find a record of DMV’s reasons for adopting the standard. However, a review of federal proceedings concerning motorcycle noise may prove helpful.

EPA initially proposed a graduated reduction in maximum permissible noise level for street motorcycles from 83 to 80 to 78 dB, for the 1980, 1982, and 1985 model years, respectively. Final EPA regulations called for maximum levels of 83 dB for motorcycles manufactured in model year 1983 and 80 dB for motorcycles manufactured in model year 1986 or later.

EPA heard testimony from motorcycle manufacturers and others on the optimum noise level for street motorcycles. Manufacturers favored a limit of 83 dB, saying it would be too costly to meet the lower standards. (Suzuki testified that its manufacturing costs would triple if EPA required it to meet the 78 dB standard. )

EPA argued an 83 dB limit would not produce sufficient benefit to the public. EPA eventually chose the 80 dB standard instead of the 78 dB standard, concluding it would benefit the public while involving less costly changes for the manufacturers (Environmental Impact Statement for the Noise Emission Regulations for Motorcycles and Motorcycle Exhaust Systems, EPA Office of Noise Abatement and Control, December 1980).

These regulations apply to most motorcycles produced in 1986 and later (40 CFR 205. 152). Manufacturers of after-market motorcycle exhaust systems must meet the noise limits for the model year for which they were manufactured (40 CFR 205. 166). Different EPA standards apply to motorcycles manufactured before that date, and to mopeds and off-street motorcycles (dirt bikes).


Table 2, below, shows the total number of all motor vehicle noise violation cases during FY 02-03, broken down by disposition. Most of these cases were for improper or defective mufflers.

Table 2: Disposition of Motor Vehicle Related Noise Violations,

FY 02-03


Causing Unnecessary Noise (14-80a)

Improper/Defective Muffler


Exceeding Decibel Limit


Total Dispositions








Paid through Infraction Bureau




Bond Forfeiture




Failure to Appear




Nolle, Dismissal, or Not Guilty




Source: Judicial Branch

PF: ro