Clearing the Air:

Misconceptions About Sound

Published in the October 2011 Issue October 2011 Feature Dustin Pancheri
"The SLP silencer on the right is 13.5 lbs. lighter than the stock 2010 M8 silencer on the left, yet both have a very low sound output.
"This is the decibel meter used to register sound coming from silencers and other products.
"When shopping for a silencer, a good suggestion is to ask about the construction of each unit. For example, SLP hand welds and individually inspects each silencer to guarantee quality before they're shipped.

Most people who have been around the snowmobile industry very long know that Starting Line Products is all about building quiet performance exhaust systems. It started 13 years ago when the company made a major push to develop a brand focused on lightweight exhaust systems that were quieter than what consumers had seen in the past.

SLP introduced the concept in the fall of 1999 and called it Era 2000 silencing technology. SLP has been building on the concept ever since. Today, as the snowmobile community deals with new sound laws as well as assorted other issues, it is more important than ever that we as riders and manufacturers be more sound conscious.

Individual states are getting more aggressive regarding noise issues. In fact, Colorado recently passed a sound law that requires all snowmobiles manufactured on or after July 2, 1975 be no louder than 88 decibels using the new stationary sound test. Many states have implemented sound laws in the past but they have been difficult to enforce in the field until recently when a new way of testing snowmobile exhaust sound emissions was developed.

This new test is called the SAE J2567 stationary sound test and unlike most previous tests where the test was performed as the snowmobile accelerates by, this test is a non-moving test. Why is this significant? The moving tests were designed to be performed in very specific controlled environments. Because some of these tests are high speed tests, they are not practical or safe to be performed by law enforcement in the field. Additionally, with the moving tests, the meter measures a combination of total vehicle noise including track noise, air intake noise, clutches and exhaust, as well as other noises from the surrounding environment.

To address these concerns, a stationary sound test was designed, allowing the exhaust noise to be isolated from other chassis and environment noises. With this new test, an excessively loud exhaust system can be pinpointed in a practical, safe manner.

This stationary sound test was developed by the Society of Automotive Engineers (SAE) for the snowmobile community. SAE is an organization that describes itself as "a global body of scientists, engineers and practitioners that advances self-propelled vehicle and system knowledge in a neutral forum for the benefit of society." They are often consulted and contracted by governments and other entities to help create standards and procedures that are fair and unbiased, which is what they did for the snowmobile community with the introduction of J2567 in 2004. Since then, states have started using the test, or a version of it, as one of the official measurement procedures used for sound testing a snowmobile.

But some in the industry, mostly a few riders, don't want sound restrictions. I have listened to some of the reasons why, and in the end, their reasons are mostly made up of misconceptions . misconceptions that are either based off old technology and what the industry used to be capable of producing or a selfish attitude and naivete towards those we share the backcountry with.


Misconception No. 1: Sound Laws Are A Bad Thing

Sound laws are a good thing for all off-road groups, but only if two things happen. First, we comply with the law in order to make it effective. Second, the law has to be enforced for those who don't comply. If every off road user complies, one more issue is eliminated from the list of things that could potentially be used against us by those who are fighting to take away our riding areas. This is one of the main reasons Colorado created a new sound law-to protect riding areas. It was easier to set a sound law that is based off of what is good for the snowmobile community and other backcountry users than wait until it is too late and let other influences set the law to a level that is unreasonable. So in simple terms, yes, this is a good thing, a change in the right direction. It's a way to ensure that our riding areas remain open.


Misconception No. 2: If A Silencer Is Quiet, It Must Be Heavy

This misconception came about mainly because most of the aftermarket silencers that were lighter than a stock unit were typically much louder than the stock unit. But in recent years silencing technology has advanced and we have been able to implement new designs that use a smaller, lighter body while still maintaining low sound output. This is evident in the latest offerings from SLP. Take for example the lightweight silencer the company builds for the 2010-11 Arctic Cat M8. It is 13.5 lbs. lighter than the stock silencer, yet when tested using the stationary test, the silencer is nearly as quiet as the stock silencer and easily passes the test. The same is true for the new silencer for the 2011-12 Ski-Doo E-Tec 800. It is almost 10 lbs. lighter than the stock silencer yet nearly as quiet. And again, it passes the new Colorado sound law.


Misconception No. 3: Quiet Silencers Make Less Horsepower

In recent years it has become more difficult for aftermarket companies to create silencer designs that are more powerful than the stock silencer. Due to advancements in fuel injection systems and two-stroke designs, snowmobile silencers have become quite intricate and specialized. The factories are now building silencers that have very specific flow characteristics and are designed to work more specifically with the new EFI systems. This means that testing and designing a new silencer requires a significant amount of fairly advanced equipment to monitor these new systems. Sophisticated dynamometers that use high speed digital telemetry and data logging equipment are a must in order to develop a lightweight silencer that, at the very least, will produce the same amount of horsepower as the OEM. Now throw in the added dimension of trying to make the silencer lightweight and quiet and it makes for a design process that has become quite expensive and time-consuming.

But SLP has spent the last 40 years building state-of-the art high performance exhaust systems, 13 of those years with a major focus on quiet technology. This has given SLP an idea of what works and what doesn't and the company uses this experience to help develop products for the latest EFI systems. Since SLP already owns the expensive test equipment, it can use those assets as building blocks to adapt and develop the specialized technology and processes required to build lightweight silencers that are quiet and either maintain stock horsepower or even produce more horsepower than what you see with the OEM silencer.

Misconception No. 4: One Loud Machine Won't Make Much Difference

One loud machine can in fact ruin it for us all. Let's think this through. Most snowmobilers have to load and unload at their house or garage every time they go riding, sometimes even in the wee hours of the morning when the neighbor just barely got little Johnny back to sleep. Some have to load and unload in a multi-use parking lot, right next to Mr. and Mrs. Smith who love the backcountry because of its peace and quiet. Others might have to ride by a parcel of private property or maybe the trail even goes through private land. Some will ride in an area that frequents cross country skiers, snowshoers or dog sledders. The point is, all it takes is one person riding a loud machine around someone who is looking for a reason to fight against our industry and it can lead to our riding areas getting shut down.

But if we load and unload a quiet machine, the people around us think less about what we are doing and our impact on their daily life. If we aren't making much noise, they may not even notice us, and if they do, they may not think much about us. Better yet, even if they do think about it, we are acting in compliance with the law which makes it harder for them to put negative pressure on our industry.

So let's summarize and get down to the hard-core facts. We know that it is possible to build a quiet aftermarket silencer that is powerful and light and we know that we need to be the ones to take responsibility and protect our riding areas. So where is the downside to riding with a quiet aftermarket silencer?

Riding a quiet snowmobile, or anything off-road for that matter, has no negative impact on our riding experience. This means riding a quiet machine is without a doubt something we all should make a priority. 

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