Why are some motorcycles incredibly loud and others hardly noticeable? The answer is simple. The quiet ones are equipped with their original equipment exhaust systems. The loud ones have had either their original equipment exhaust systems modified, or replaced with an aftermarket exhaust system by their owners. The most common reasons these vehicle owners give for this modification is that they are improving their safety, and usually spout slogans like "loud pipes save lives". In reality there has never been a credible study done by anyone that proves or even supports this erroneous theory. To the contrary, there are several that prove otherwise. Others say they want to "make it sound like a bike" or to "get some attention". Both groups of these vehicle owners seem to be oblivious to the damage they are doing to the image of the motorcycling community.
Motorcyclists' rights groups and industry trade journals all try to defuse and obfuscate this issue by placing subjective values on excessive motorcycle noise and reply to criticism with comments such as: "what might be loud to some is not loud to others". They try to shift responsibility of this problem to the general population labeling law-abiding citizens as "complainers". These groups avoid discussion or even the mention of the serious health effects of excessive motorcycle noise.
Many of these modified motorcycles can reach noise levels in excess of 100dB(a); a level that easily triggers an involuntary stress response commonly known as "flight or flight" response. This results in the secretion of adrenaline, with ensuing spikes in cardio-respiratory rates, muscle tension, and elevated blood pressure. This "flight or fight" response may be the perfect stimulation to get bikers ready for a ride but, for people trying to relax or sleep, or even engage in ordinary activities around the home, the never ending cycle of arousal constitutes a serious health issue. It is this fact alone that led Congress to create the Noise Control Act (NCA), and led the EPA to create a simple enforcement tool specifically for local level law enforcement called the "label match-up."
The "label match-up" came about because the EPA realized that the intricacies of accurate field-testing are beyond the scope of most law enforcement agencies. They therefore created regulations that require manufactures (starting in 1983) to test and label each motorcycle and its corresponding exhaust system under laboratory conditions.
As part of the NCA, the "label match-up" plan provides a valuable enforcement tool by removing all doubt for police as to what is an acceptable motorcycle muffler. Quite simply any motorcycle (1983 and newer) not displaying the required muffler labeling (as originally equipped) stating "this exhaust system meets EPA noise emissions requirements" is subject to fines.
Unfortunately due to budget constraints the EPA closed its Office of Noise Abatement and Control, leaving this last job uncompleted. This was to disseminate legislative examples of the label match-up to states and localities. Currently the EPA is only active in the area of manufacturer regulations.
The framework of the "label match-up" has been in place since 1983. All that is needed is legislative examples for states and municipalities. The popularity of the type of motorcycles that use loud exhaust systems is at an all-time high. Motorcycle industry marketing sales departments have seized upon this trend by offering ever-louder exhaust systems, arrogantly advertising that mufflers may be easily gutted for use as an open header.