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Home > Technical Articles
Sound Issues
By Jerry Mathews
Noise is nothing more than an audible sound … and it seems everyone's perception as to whether this sound is pleasant or annoying is different.

   Sound that is music to one's ears can be noise to another's. Snowmobilers may ask, "Why is there so much commotion coming from the Department of Natural Resources (DNR) and state snowmobile associations with regards to snowmobile noise? Are they just trying to harass the snowmobile community and take their money?"

   For the most part, the DNR and state associations are just trying to protect our sport the best way that they know how. We rely on public and private land for our trail systems. Public lands are constantly under scrutiny by different environmentalist groups while upset land owners are closing private lands.

   Environmentalists are trying to close public lands to winter recreation. However, our tracks don't last and therefore you cannot even tell where we have been when the snow melts in the spring. Furthermore, animals have either migrated out of our snowmobiling areas or they are hibernating deep in some cave under the snow. We don't hurt anyone or anything by using these lands for our winter recreation, do we?

   Environmentalists are saying that in national parks the noise of the snowmobile hurts the animals by frightening them. Well, if the noise of a snowmobile frightens the animals, why do they just stand at the side of the trail when you go by? Furthermore, all snowmobiles have to be noise emission certified before being sold to the public.

   Most states require sleds to pass one of two tests that were developed by the Society of Automotive Engineers (SAE). These tests are either the SAE J192, an acceleration test through a 150-foot trap with a maximum decibel level of 78 dB at 50 feet, or the SAE J1162, a 15 mile per hour pass by test with a maximum decibel level of 73 dB at 50 feet (see diagram). These tests insure that all stock snowmobiles meet the sound level criteria demanded by each state.

Quieter Than SUVs
   Stock snowmobiles are as quiet or quieter than most sport utility vehicles, pickup trucks, vans, busses and large trucks. In fact, in controlled tests we at SLP found a 1999 Ford F-250 Powerstroke diesel 4X4 pickup truck to be 77.7 dB and a 1995 Chevrolet K1500 350 gas 4X4 pickup truck to be 77.1 dB as tested by SAE J192 testing procedure. Why aren't they being targeted for excessive sound levels by the environmental groups?

   Stock snowmobiles are reasonably quiet when compared to other forms of transportation. Although we need to respect our environment and do everything in our power to save it for generations to come, we should be able to enjoy our surroundings. All people should have an opportunity to see the beauties of a national park in the dead of winter. They should be permitted to see spectacular sunsets from a high mountain ridge and witness the wind blown snow, frozen to the trees, overlooking a vast array of white. The term "all people" is the key. By closing more areas to motorized travel, many people who are physically challenged, or chose not to participate in certain forms of outdoor activities, will not be able to enjoy these areas. This is a form of discrimination and should not be allowed.

   There are currently sufficient areas inside, as well as surrounding our national parks, set aside specifically as non-motorized vehicle areas (most commonly known as Wilderness areas). For example, out of 3,472-square miles of land in Yellowstone National Park, there are only 370 miles of paved roads with 458 campsites compared to approximately 1,200 miles of backcountry trails with approximately 300 backcountry campsites (Yellowstone National Park Facts). Also, in Idaho's national forests, there are 2766.8-square miles of land that is designated as Wilderness (Bureau of Land Management). There are also many other Wilderness areas scattered throughout the West. These areas offer the solitude seeker the chance to really become one with nature, but because access is limited, only a few people have time and are physically able to enjoy these areas.

Restricted Access
   Some private landowners are also closing access through their lands. This is partially due to the fact that times are changing. We are seeing a large migration of people from urban areas to more rural areas. These people are seeking the solitude that the country is supposed to offer.

   Many have never been around snowmobiles and do not realize that a snowmobile trail runs right past their property. Winter comes and they are very surprised at the number of snowmobiles that pass by their houses each day. They are also surprised when traffic does not stop at dark. They usually tolerate this until a few inconsiderate people insist on riding irresponsibly through these populated areas (especially at night).

   This new landowner then draws the conclusion that having this trail run across or past his property is an annoyance as well as being dangerous for his community. Then he does all he can to get the trail closed or rerouted. There are also a number of property owners who have allowed access across their lands for many years. However, when the inconsiderate snowmobiler insists on racing across his property in the middle of the night or does some type of damage to the property, the landowner gets upset and closes access across his land.

   Even though sound levels are just one contributing factor to these land closure issues, they have been targeted as the root of the problem over the past three years at the International Snowmobile Congress (ISC). The International Association of Snowmobile Administrators and state associations, alike, have been working hard on these problems but there doesn't seem to be an easy answer.

   As mentioned previously, stock snowmobile noise levels are strictly regulated, however, there are a number of people who modify their snowmobiles to enhance performance. A popular modification is to remove the stock exhaust system and replace it with an aftermarket system.

   In the past, aftermarket systems have typically increased the noise level somewhat (in some cases immensely), as well as boosted the power. This practice has been widely accepted and wasn't a large problem until just recently because these sleds were mostly used for racing, not pleasure riding.

   With more and more snowmobilers modifying their sleds and using them strictly for pleasure riding, it makes noise level enforcement difficult. The two tests the OEMs are required to pass are difficult to conduct and enforce in the field.

Proposal To Ban Aftermarket Systems
   Two years ago at the ISC there was discussion to ban the modification of exhaust systems altogether. However, over the past two sessions of Congress, it has been resolved by the state associations, DNR, aftermarket companies and the OEMs to work together in order to design a field friendly testing method. Also, most of the aftermarket manufacturers who design and produce exhaust systems have resolved to manufacture only quiet systems.

   In the future, you will see more and more law enforcement personnel enforcing noise ordinances. Currently these officers are relying on an ordinance that states, "No person shall operate a snowmobile unless it is equipped with a muffler in good working order which blends the exhaust noise into the overall engine noise and is in constant operation to prevent excessive or unusual noise" (Wisconsin Department of Natural Resources). This type of an ordinance is vague and leaves the interpretation of excessive or unusual noise up to the officer.

   Within the next year or two they will have a sound test procedure at their disposal that will be easy to conduct in the field. This will create a more fair enforcement system and will, in the end, be what we need to force sound levels down.

   In order to further help the sound level problem, on June 8, 1999, International Snowmobile Racing (ISR) published the following statement: "In a continuing effort to enhance the public image of snowmobile racing, the various rules committees within International Snowmobile Racing have agreed that all snowmobiles in all forms of competition will be required to have an effectively silenced exhaust system by June 1, 2000."

   This will help quiet racing arenas down, eliminate racers operating unsilenced racing snowmobiles on the trails and give spectators a more realistic view of snowmobile sound.

Personal Harm
   As well as being an annoyance to others, excessive sound levels can be damaging to us snowmobilers. Jim Fairchild, the technical manager at SLP, was an accomplished racer in his day. He raced in an era when glass pack silencers and open stingers were the norm. Today, he has only 25 percent of the hearing remaining in both ears. He cannot stress enough the need for lower noise levels. Jim said, "If I had it to do all over again, I would have insisted on quieter systems." In fact, if you call SLP for technical assistance, don't be surprised or offended if he asks you to repeat yourself.

   Law enforcement and environmentalists need to realize that banning or unreasonably restricting the sale of aftermarket exhausts and restricting trail access will have an effect on the economy in many areas. Dealers rely on aftermarket product sales in order to stay healthy. Unfortunately, most dealers cannot sell snowmobiles for the suggested retail price.

   In fact, a large number of dealers barely break even on new unit sales and therefore are forced to rely heavily on aftermarket parts sales in order to make up the difference. Aftermarket pipe sales help to make dealers more profitable so that they can employ more people to service their customers properly. Also, many small towns throughout the snow belt rely on snowmobile tourism as their main source of income. Annual expenditures by snowmobilers on our sport in the U.S. are over $6 billion dollars (International Snowmobile Manufacturers Association).

Sound Off
   When it comes to noise, sound is measured in decibels. Peter Elsea said, "Our perception of relative loudness is somewhat logarithmic. Because it is logarithmic, for every 10 dB increase, we hear the sound as twice as loud. However, a 3 dB increase would be just noticeable." To give an idea of sound levels, an air conditioned room would have a dB level of between 60 and 65. A person speaking in the room would be 65 to 75 dB. A stock snowmobile can be as loud as 78 dB as measured by the SAE J192 test. Oddly enough the sound level is normally lower from a rider perspective than it is from an observer within 50 feet of the trail.

   At SLP, we have been testing noise levels of our products for years, However, this past season we really put a big emphasis on it. In fact we even took our sleds to the West Entrance of Yellowstone National Park where sound tests were conducted on snowmobiles to assure they meet the legal sound limit before the sleds enter the park.

   The test being used is a version of the SAE J192 test. Montana law states all snowmobiles have to meet a 78 decibel maximum as stated in the SAE J192 test. The SAE J192 test states, "A 2 dB tolerance over the sound level limit shall be included to provide for variations in test site, temperature gradients, wind velocity gradients, test equipment and inherent differences in nominally identical vehicles. It has been observed that under some test site conditions, variability in test results greater than 2 dB can be experienced.

   To allow some margin of error created by ever changing conditions, Yellowstone National Park has been allowing a 4 dB grace. Any snowmobile that is tested above 81.9 dB is not allowed through the gates of the park.

SLP's tests results are as follows:
  Test 1 Test 2
Arctic Cat 600 Powder Special:
SLP ‘99 Production Lightweight Silencer 81.6 dB 83.7 dB
SLP ‘99 Production Twin Pipes 82.4 dB 84.2 dB
Polaris 700 XC with 2-inch paddle track conversion:
Stock exhaust 78.3 dB  
SLP ‘99 Production Single Pipe 81.1 dB 81.1 dB
SLP Prototype ERA 2000 Single Pipe 78.2 dB 79.7 dB
Polaris 600 XC:
SLP ‘99 Production Single Pipe 79.3 dB  
Polaris 700 RMK:
SLP ‘99 Production Twin Pipe 78.5 dB 78.9 dB
Yamaha 700 Mountain Max:
SLP ‘99 Production Triple Pipes 84.5 dB 83.2 dB
SLP Triple Pipes with Prototype Silencer 76.1 dB 76.1 dB

   We usually made two runs to verify the data. As you can tell, some of our products met the Park's criteria, some did not. We are redesigning all of our products that didn't meet the Park's criteria so they will pass.

   As you can see by the above data, it is possible for us as well as other aftermarket companies with the use of new silencing technology to manufacture exhaust systems that provide more performance and pass the SAE J192 test. Being the fastest with a quiet system is more pleasurable than doing it with a loud one.

   With the sport of snowmobiling growing as rapidly as it has for the past five years, a certain number of problems are to be expected. These problems are occurring throughout the snow belt. Trails and public lands are being closed in the West as well as the Midwest and East. Some of these areas have been around for many years.

   As snowmobilers, we need to remember that even a stock snowmobile can be an annoyance when used aggressively in populated areas, especially at night. The snowmobile marketplace is consumer driven. Therefore it is the end user's responsibility to demand quiet products from the aftermarket sector as well as operating their snowmobile with extra courtesy in populated areas, again especially at night.

   We must face the reality that as hard as we try, some of our trails will be closed. We will also be faced with more restrictions such as reduced speed limits, curfews and in some cases, relocation of trails. These changes will affect the way we snowmobile. However, it is better than the alternative of snowmobiling areas being closed altogether.

   The bottom line is that we need to protect the areas that we enjoy riding in.
"Setting the World's Performance Standards"