and Canada. Some of the participants in recent years have been the École polytechnique de Montréal with a Quasiturbine engine and students from École de technologie supérieure of the UQAM with a less polluting two-stroke engine using E85 and direct injection. Noise Maximum noise restrictions have been enacted by law for both production of snowmobiles and aftermarket components. For instance, in Quebec (Canada) noise levels must be 78 decibels or less at 20 meters from a snowmobile path. As of 2009, snowmobiles produce 90% less noise than in the 1960s but there are still numerous complaints. Efforts to reduce noise focus on suppressing mechanical noise of the suspension components and tracks. Arctic Cat in 2005 introduced "Silent Track technology" on touring models such as the T660 Turbo, Bearcat, and some M-Series sleds. Ski-Doo has since then also used comparative "silent track technology" on some models. The use of aftermarket exhaust systems ("cans" or "silencers") is controversial. These replace the stock muffler with a less restrictive system that is usually claimed to increase power output of the engine. However, these aftermarket exhausts are often much louder than those from the factory, with only some being slightly quieter than a completely open, unbaffled system. Most, if not all, local snowmobile clubs (that maintain and groom trail systems) do not recommend them because of noise. Local and state authorities have set up checkpoints on high-traffic trails, checking for excessively loud systems and issuing citations. Typically these systems are installed on two-stroke powered machines (giving the distinctive "braap" sound); however, in recent years aftermarket companies have released silencers for four-stroke models as well. Importance in isolated communities Since the invention of snowmobiles, isolated communities of northern North America have always had a demand for them. However, the early snowmobiles designs were not economical or functional enough for the harsh environment of northern North America. Joseph-Armand Bombardier started producing the Ski-Doo in 1959 at the request of a priest. The priest had asked Bombardier to make an economical and reliable means of winter travel. The Ski-Doo greatly changed life in northern North America's isolated communities, where Ski-Doo replaced sled dogs by the end of the 1960s. The Ski-Doo also greatly improved communication between isolated communities. Snowmobiles are also called "Snow Machines” in some areas of Alaska. Work In northern North America, historically, isolated communities depended on dog sledding and snowshoeing as their primary method of