Ever wonder why some motorcycles are so quiet and others are so loud?

Contrary to popular belief, motorcycles are not manufactured to be loud. When motorcycles come from the factory, they are reasonably quiet–because they are factory- equipped with effective mufflers.

All highway and off-road motorcycles manufactured since 1983 are regulated by federal law under the authority of the Noise Control Act of 1972, which is still in effect. Federal regulation 40 CFR 205, parts D&E regulates their total noise emissions. It also regulates their mufflers and requires motorcycles to be equipped with EPA-approved mufflers, not just when leaving the factory, but at all times while they are in the United States. It is a violation of federal law to tamper with the emission control devices of motorcycles–even those devices that control their noise emissions (their mufflers).

Excessively loud motorcycles are the result of the deliberate action of their owners to alter their exhaust system–which is illegal. The most common form of illegal tampering is removing factory equipped EPA-approved mufflers and replacing them with after-market mufflers or entire exhaust systems that are not EPA-approved. Those after-market exhaust mufflers are not designed with effective exhaust noise suppression as a primary design goal. They are designed to increase the exhaust noise of motorcycles and their manufactures openly admit they are intended “for use on closed courses only.” Those types of exhaust systems are not legal for use on highway motorcycles.



According to the National Highway Traffic Safety Administration, there are over eight million motorcycles registered in the United States. A significant percentage of motorcycles operating in the United States have been illegally equipped with after-market exhaust systems which are not EPA-compliant.

In its analysis for the noise emission regulations for motorcycles and motorcycle exhaust systems, the United States Environmental Protection Agency concluded that a significant portion of the problem of excessive motorcycle noise was due to motorcycles with after-market exhaust systems and to tampering with the original equipment exhaust system. That problem persists today, and if anything, has grown worse and is the root cause of excessively loud motorcycles.

The EPA stated that motorcycles with either modification listed above could easily increase noise emissions to over 100 dBa. They also realized that although motorcycles only account for two or three percent of total vehicular traffic mileage, and because they are presently among the noisiest vehicles in the traffic stream, any reductions in motorcycle noise would have a significant impact upon overall traffic noise and benefit the public.

A mere one hour of exposure to noise levels at 94 decibels can damage your hearing. If the noise is 100 decibels, it only takes 15 minutes for hearing damage to occur. But hearing damage is not the only adverse effect excessively loud motorcycles have on the public. Unlike legally equipped and quiet motorcycles, the excessive noise of many illegally modified motorcycles can be heard for miles. Excessive motorcycle noise poses a severe public nuisance and health hazard and adversely impacts the public’s quality of life.

According to a Motorcycle Industry Council’s 2008 Owner Survey, 38% of on-road motorcycle owners replace or modify their exhaust systems. Cruisers are the most common type of bike with a modified exhaust, followed by sport bikes, touring models, and competition dirt bikes.

The California Air Resources Board reports the following: “One of the more popular modifications today is replacement of the original exhaust system with aftermarket exhaust systems and parts.”

And according to a California Air Resources Board survey of 2003 to 2007 model year highway motorcycles, “85 percent of newer motorcycles in Southern California (primarily Harley Davidsons) had some form of exhaust modification. After-market exhaust systems on highway motorcycles can range from straight pipes without any catalysts to systems with catalysts that have not demonstrated durability and/or the ability to effectively control emissions.”

The large displacement V-win motorcycles manufactured by Harley-Davidson are among the most commonly modified with the use of after-market non-EPA compliant exhaust systems. Not surprisingly, they are also among the loudest motorcycles on the road and elicit the bulk of citizen complaints about motorcycle noise. “We usually see 60 to 70 percent of riders change the pipes out,” according to the general manager at a Boston Harley-Davidson dealership. But motorcycles made by Harley-Davidson are not the only motorcycles being illegally modified to make noise; the problem is present with other brands of motorcycles as well.

It is very clear that there are many loud motorcycles in the United States. It is also very clear why so many on them are loud: they have been illegally modified. Also, the solution to the problem is not too difficult to deduce. The laws and regulations prohibiting those unlawful acts must be enforced.


The role of the federal government

The role of the federal government is to establish noise pollution regulations where necessary. In the 1980’s, when the EPA’s Office of Noise Abatement and Control (ONAC) was in operation, it established noise emission limits for highway and off-road motorcycles. The purpose of those regulations was to provide a minimum of protection to the public from excessive motorcycle noise and to establish a national uniformity of treatment for the that source of noise pollution.

Lack of federal enforcement

In spite of the Noise Control Act of 1972 and Subparts D and E of Part 205 of Title 40 of the Code of Federal Regulations, the EPA is currently taking little or no action against illegal motorcycle noise. The EPA’s standard response to noise pollution related inquiries is that dealing with noise pollution “is best left to the states” and cites “lack of resources” as an excuse not to enforce federal noise pollution regulations.

By the “lack of resources” response, the EPA is referring to Congress defunding its Office of Noise Abatement and Control in 1981. In effect, the EPA is claiming that Congress is not allowing it to regulate noise pollution or enforce the Federal noise pollution regulations that are still on the books and in effect. Because of that bad policy decision by Congress, the EPA does not currently see noise pollution to be within its purview and remains inert in carrying out the intent of the NCA of 1972. The result of that bad policy: out of control and ever-escalating noise pollution. And in the case of motorcycles, an out of control motorcycle noise pollution problem.

We disagree with Congress’s and the EPA’s position on the noise pollution issue and on the EPA’s excuses for not enforcing any federal noise pollution regulations at all. That policy must be changed. That will require lobbying Congress to direct the EPA to include noise pollution within its purview, provide funding for enforcing and revising at least one federal noise pollution regulation: 40 CFR 205, parts D&E (the federal motorcycle noise and muffler regulations).

Is it really best to leave noise pollution control entirely up to the states? No. Ever since Congress defunded the federal noise pollution control program, the states have done nothing to take up the slack. Without federal assistance and involvement, the states terminated their noise pollution control programs and their efforts to enforce their motor vehicle noise and mufflers are weak.

It is vitally important for the federal government do its part in making sure the motorcycle industry complies with the federal manufacturing regulations for motorcycles and make sure the industry is manufacturing legal EPA-compliant mufflers for motorcycles. That is something the states cannot do and where federal action is essential.

The Role of the States

What have the states done about regulating motorcycle noise emissions? The short answer is: not much.

Most state laws simply require “mufflers” without clearly defining what proper mufflers are. They only require that the mufflers “prevent excessive usual noise” and leave the interpretation of that up to local law enforcement and the courts. Usually, they will allow virtually any “muffler” and leave the state and the police with the burden of proving that the noise emissions of motorcycles equipped with competition-class mufflers are too loud.

The advocates of “loud pipes” (a term often used to describe illegal exhaust noise enhancing motorcycle exhaust systems) love what they see as “anything goes” muffler laws and exploit them with vigor and vehemently oppose more precise muffler laws that prohibit the types of mufflers and exhaust systems they want to use on their motorcycles. They hate tampering prohibitions and seek to have them removed, or at least, unenforced. Their disdain for muffler standards and tampering prohibitions provides a hint as to what should be done to effectively mitigate the problem. Establish motorcycle noise limits, muffler standards, tampering prohibitions, and actively enforce them.

The Role of the Police

The role of the police is to enforce the motor vehicle noise and muffler laws of the states and the ordinances of their political subdivisions.

To do that, all the police have to do is follow these four simple steps that they have been authorized to follow for years. And yes, the police have to expend some energy, as no law enforces itself.

The four-step process:

1.Observe the plainly audible excessive noise emitted by a loud motorcycle.

2. Stop the vehicle.

3. Issue the appropriate citation.

4. Show up in court and testify to what was observed and what law was obviously violated.

That simple four-step process should be very familiar to police departments and the police should already be very adept in employing it. The police just have to employ it for dealing with excessively loud motorcycles and not be hesitant in doing it.

However, many cities and police departments do not take the issue seriously and do not have the will to enforce motor vehicle noise laws. Others look for gimmicks that don’t require any effort at all on the part of the city and its police department, such as asking the operators of loud motorcycles that have been illegally modified to be loud to operate their loud motorcycles” quietly” when in town, which is essentially impossible for them to do and is a totally silly and useless motorcycle noise control policy. There is a much more practical way to enforce motor vehicle noise laws.

Employ the “excessive or unusual noise” enforcement criterion

The motor vehicle exhaust noise and muffler laws of practically all 50 states have one key phrase in common: “excessive or unusual noise.” The simple observation of excessive or unusual noise is the enforcement criterion employed by most police officers when enforcing motor vehicle noise and muffler laws.

Although establishing prohibited decibel levels in noise pollution regulations has its place in some instances (such as for products distributed into commerce at the regulatory level), dealing with everyday “in use” and local noise pollution issues by establishing “allowed noise” levels expressed in decibels is not the best way to address the problem, especially for enforcement purposes (and especially for mobile and transient sources of noise such as motorcycles).

Employing a decibel-level based approach for establishing “allowed” noise levels implies that one is “allowed” to make noise and gives the impression that the noise one is “allowed” to make must be assessed by performing decibel-level noise measurements; that approach is inherently enforcement inhibiting and puts a damper on having such noise pollution policies enforced. It is far better to establish what a noisemaker can’t do rather than what a noisemaker can do.

The simple observation of “excessive or unusual noise” emitted by a loud motorcycle provides the police with valid probable cause to stop and ticket its operator. That simple enforcement criterion has been upheld by the appellate courts as both objective and constitutional. The police should not hesitate to employ it.

Exhaust system inspection

The best way to follow up the stop is to have the vehicle’s exhaust system and mufflers inspected, which greatly augments that enforcement approach and provides additional objective evidence; that evidence being the presence of an illegally tampered with exhaust system or improper mufflers which constitutes an equipment violation and is the root cause of the observed “excessive or unusual noise” emitted by the motorcycle. That inspection can either be perform by a properly trained police officer or by a properly-trained state authorized and supervised inspection mechanic. State laws should be revised to incorporate that enforcement approach.

Quill Driver Books of Fresno, California recently published Guide to Modified Exhausts: A Reference for Law Enforcement and Motor Vehicle Inspectors, written by Noise Free America: A Coalition to Promote Quiet. The information in the guide is intended to provide jurisdictions and law enforcement officers a means of dealing with the problem of excessively loud motorcycles that does not require the use of expensive sound measuring equipment or the necessity of conducting time consuming and cumbersome exhaust noise tests. It offers an alternative method to address the problem that is based on a simple, common sense approach based on exhaust system equipment standards.

Please view this Power Point presentation on the issue of illegal motorcycle noise:!Aux9H6ZL5f4mgypyD45HZLoLfkCZ

Please consider purchasing our book, Guide to Modified Exhaust Systems: A Reference for Law Enforcement and Motor Vehicle Inspectors, available from Quill Driver books. Please consider asking your local law enforcement agencies to purchase the book for all of their officers.