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Noise regulations are finally starting to make some sense.
The new Wisconsin sound rules, which are likely to be adopted over time in other states, set a sound standard (SAE J-2567) of 88 decibels that is satisfactory to landowners and trail developers, without adding unreasonable cost and weight to your snowmobile.
Wisely, the rules were a collaborative effort, a 5-year process, between Wisconsin's Department of Natural Resources, snowmobiling clubs, the Big 4 manufacturers and the I.S.R. Aftermarket Committee. The agreement is good news for everyone, but particularly for the Big 4 who are already spending big money on meeting stricter federal emission requirements.
The noise issue is nothing new to snowmobiling though.
Big noiseExcessive noise was one of the first big problems the snowmobile community had to tackle during the snowmobile boom of the '60s and '70s.
By the early 1970s the industry was in its prime, and manufacturers were more interested in getting units out the door and hoping they stayed together, than in refining mufflers. Often the result was snowmobiles being built using converted industrial engines with simple mufflers, many of which were running at or above 100 decibels - dB(A). Decibel (dB) is a unit of sound measurement and the (A) refers to a frequency scale that closely matches that of the human ear.
The scale is often difficult to understand as it is a logarithmic scale, not a linear scale. A linear scale would have to be very long to cover the full range of the human ear, so the logarithmic scale is used, which doubles the sound pressure for every 6 dB(A). Using this logarithmic scale, to cut the sound in half from 100 dB(A) meant that you would try to achieve a 94 dB(A) reading. Cutting the sound in half again would give you 88 dB(A).
So 88 dB(A) is a 75% reduction in noise from the old 100 dB(A) level. Also, once you get much below 90 dB(A) using a muffler, other sounds such as intake noise and mechanical rattles from pistons, etc., become more apparent.
Larger silenced air boxes and water-cooled cylinders help dampen the noise from these two areas, but new problems show up as levels are lowered further. At 84 dB(A), track noise becomes more noticeable with the introduction of slide rail suspensions, and then all kinds of chassis noises from suspensions and skis start showing up.
But back in the early 1970s there wasn't a good understanding of all those noise sources. Tracks were quieter back then as most ran on rubber boggie wheels.
Unfortunately, in order to please legislators from the '70s, a somewhat unrealistic 78 dB(A) sound level was promised as obtainable. This sound was measured at a distance of 50 feet as the machine accelerated past a sound meter at full throttle with a 75 ft. run-in.
Soon it became clear that the running surface - trail conditions - had a large influence on the sound reading. The difference in readings between hard-pack trails and 10 inches of powder could be as much as 10 dB(A).
For engineering reasons it was then decided to do testing on grass, to obtain better consistency. This may not make immediate sense, but a lot of engineering testing is done in the summer. Winters are only 3-4 months long in most areas, and it's easier to consistently find grass throughout the course of a year than snow.
Tips from boatersI worked for Evinrude during the early '70s, and management felt the firm could gain a larger share of the market if it made a very quiet snowmobile. This had proven a good strategy in the outboard motor market. The result was the "Q" machine in the Evinrude brand and the "Golden Ghost" Johnson sled.
Unfortunately, these sleds gained quite a lot of weight in the process, while losing power. Although some customers liked the quiet machines, the fact that they weighed 150 lbs. more than the competition and had 20 fewer horsepower, soon cut into sales. Customers preferred light, powerful machines with a somewhat quieter muffler, so the "Quiet Elephants" soon became white elephants living in warehouses.
Other manufacturers took note of the "quiet" failure, and although they improved their machines in the sound department, they closely watched both power and weight to obtain maximum performance. This all did little to encourage quieter machines, and as it turned out, nobody checked for noise anyway.
Change hits hardThis nonchalant attitude changed in the early 1990s when a California-based motorcycle aftermarket company started offering bolt-on silencers to replace sled mufflers, hoping to make some fast cash in the winter. These silencers kicked sleds' sound levels into the high 90 dB(A) range.
Some aftermarket companies chose to stay within the parameters of their quiet designs and lost market share. Others buckled to consumer pressure and jumped on the bandwagon with noisier mufflers. Even manufacturers started making their performance machines louder.
The situation simply couldn't last. Complaints rolled in from landowners who were sick of being awakened in the middle of the night by "Mod Blasters" and "Rumble Packs." So the DNR cracked down and started handing out tickets, but the rules and procedures were not clear to anyone, including the DNR.
First, the SAE's field engineering test was not practical for law enforcement. Without any measurement taken, some sled owners took their tickets to court and won. One judge likened such tickets to getting a speeding ticket by the officer just watching a car drive by and not getting a radar measurement!
Claiming that it was illegal to have an aftermarket system did not hold up either, as some aftermarket systems were actually quieter than some stock models, and it also went against federal Restraint of Trade legislation. This says you can't specify that a person use only original manufacturer equipment because it would create a monopoly by eliminating competition.
It's not illegal to simply use an aftermarket exhaust, but it has to meet the standard sound level. If it were illegal to mount an aftermarket system, then it would be illegal to mount a Midas or Car-X muffler on your car. What was needed was a practical sound testing procedure that could be conducted successfully on the trail by DNR officers.
The testThe first idea came from the I.S.R. Aftermarket Group, which suggested a system similar to that used for testing motorcycle sound levels. The I.S.R. began testing stock machines at racetracks with their version of a stationary test back in 2000. In the motorcycle test, the engine is revved to a predetermined rpm while the machine is stationary, and the measurement is taken at a given distance from the noise source.
Seeing the success of this system, the DNR, clubs and others began determining the rpm, distance and acceptable dB(A) numbers for snowmobiles.
Five years of tests, meetings and public hearings have brought us to the new realistic standards. The 88 dB(A) number is higher than the old 78 dB(A) engineering test because the distance to the sound meter is much closer. With the new SAE J-2567 stationary test standard, sound is now measured at 4,000 rpm, 157.5 inches (4 meters) away, rather than with a moving machine 50 ft. away.
The new rule requires the machine to be quieter than 88 dB(A), or you will get a ticket. This is a standard that should be obtainable without a lot of new expense for manufacturers or aftermarket companies, and at the same time should keep landowners and clubs happy.
It has taken the industry 30 years to finally arrive at an enforceable standard, and this time it should do the sport some good.
Olav Aaen is a long-time contributor to AmSnow. As a mechanical engineer and president of Aaen Performance, Olav has been heavily involved with snowmobile performance since 1968. Aaen Performance is best known for pioneering performance pipes and introducing the roller clutch to the snowmobile market.