Noise Free America: A Coalition to Promote Quiet

For immediate release
May 4, 2021

Ted Rueter
[email protected]

Larry Deal
[email protected]

Chapel Hill: Larry Deal, co-author of Guide to Modified Exhaust Systems: A Reference for Law Enforcement Officers and Motor Vehicle Inspectors, offers the following guidelines for dealing with motor vehicle noise.

1. In one word: Complain.
Noise ordinances are not typically enforced proactively. It usually takes public complaints to trigger enforcement.
Complain intelligently and not from a position of ignorance.
a. Look up the applicable laws. Do not rely on the authorities to know the laws.
b. Look up the state motor vehicle noise and muffler laws.
c. Look up and carefully read your local noise ordinance and see if and how it addresses motor vehicle noise.
d. Explain the laws to the authorities.
e. Ask questions and get answers.
Submit a FOIA request to your police department requesting enforcement statistics of the part of the noise ordinance you are interested in. Have your police ever witnessed excessively loud motorcycles and other vehicles on the city’s public streets and taken enforcement action? How many such actions have been taken over the past two or three years and thus far this year?
f. Inform the authorities of the laws and pressure them to enforce the laws.
g. General complaints are the weakest and easiest to dismiss and ignore.
Be specific. Identify specific vehicles. Get vehicle descriptions. Get registration plate numbers. Observe days of week and time of day and location the vehicle is most likely to be observed. Supply that information to the police.
2. Exhaust noise
The root cause of excessive exhaust noise in most cases is vehicles equipped with modified exhaust systems that are not factory-equivalent. Excessive and unnecessary revving of the engine is a secondary cause.
State muffler laws often require vehicles to be “equipped with a muffler” that is “effective in preventing excessive or unusual noise,” which refers to that underlying equipment violation. A similar term used in various state muffler laws and local noise ordinances is “ineffective muffler,” “altered muffler,” or “improper muffler.”
Dealing with excessively loud vehicles is best served by enforcing a local ordinance utilizing the “plainly audible” at a distance criterion as a civil infraction and not by an impractical motor vehicle noise law that specifies maximum noise levels for vehicles in motion or stationary. It should be obvious why that is cumbersome and not practical to enforce.
The further advantage of enforcing a local ordinance as a civil case is that the burden of proof is by the “preponderance of evidence,” which is much easier to meet than by the “beyond a reasonable doubt” standard required in some misdemeanor and felonies and that some states require in prosecuting state motor vehicle infractions.
3. Automotive sound system noise

a. Employ the simple-to-enforce “plainly audible” standard.

An objective enforcement criterion based on the “plainly audible” standard requires that the “plainly audible” sound be assessed at a specified distance from the source or perhaps under other specified conditions.
For example: In their testimony in court, some police officers who have issued citations to operators of vehicles exhibiting loud exhaust emissions testify that they objectively take enforcement action when they can hear the exhaust noise emissions of vehicles while in their patrol cars with the windows rolled up and with the suspect vehicle located at a specified distance from their patrol car. The particular distance is up the police or may be specified in a local ordinance. The distance should be a reasonable one and chosen to be easy for the police to estimate.
That provides a reasonable and objective criterion for assessing the “excessive or unusual noise” exhibited by excessively loud vehicles and for justifying stopping those vehicles and issuing their operators the appropriate citations. Police officers should testify to what they observed and to what objective criterion they used to make that assessment. That does not necessarily require the use of decibel meters and the police should not be limited to that cumbersome enforcement method specified by state laws or local noise ordinances.
4. Burden of Proof: The advantage of enforcing local noise ordinances.
Check what burden of proof standard your state employs for motor vehicle infractions that address excessive noise and their mufflers.
Some states require those violations to be proven by the “beyond a reasonable doubt” standard, which is the highest burden of proof and the most difficult to prove. That can discourage the enforcement and prosecution of state laws.
Some states employ the “preponderance of evidence” burden of proof standard for some motor vehicle infractions.
There is very important advantage of enforcing a local noise ordinance instead of a state noise-related law. Local noise ordinances are civil cases where the burden of proof is by the much easier to prove by the “preponderance of evidence” standard. That is a very important point to remember.
If your state has a very good motor vehicle noise law, lobby your municipality or county to mirror the state law in its noise ordinance.
If your state has a poor motor vehicle noise law and permits its political subdivisions to address motor vehicle noise as they choose, lobby your municipality or county to establish and enforce a local motor vehicle noise ordinance adopting the approach suggested in parts two and three.
For additional information, see