Sound levels for snowmobiles have been reduced 94% since inception. Pre-1969 snowmobiles were noisy. At full throttle, these machines emitted sound levels as high as 102 dB(A) from a distance of 50 feet.
Snowmobiles produced since February 1, 1975 and certified by the Snowmobile Safety and Certification
Committee's independent testing company emit no more than 78 dB(A) from a distance of 50 feet while traveling at full throttle when tested under the Society of Automotive Engineers (SAE) J192 procedures. Additionally, those produced after June 30, 1976 and certified by the Snowmobile Safety and Certification Committee's independent testing company emit no more than 73 dB(A) at 50 feet while traveling at 15 mph when tested under SAE J1161 procedures.
For comparison purposes, normal conversation at three feet produces approximately 70 dB(A).
It would take 256 78 dB(A) snowmobiles operating together at wide open throttle to equal the noise level of just one of the pre-1969 snowmobiles.
Problems with excessive noise levels do occur when irresponsible snowmobilers modify the snowmobile exhaust system or substitute the factory system with an after-market racing exhaust. In most states and provinces this practice is illegal and grossly misrepresents the sport.
THE BASICS OF SOUND AND NOISE
Every kind of sound is produced by vibration. The sound source may be a violin, an automobile horn, or a barking dog. Whatever it is, some part of it vibrating while it is producing sound. The vibrations from the source disturb the air in such a way that sound waves are produced. These waves travel out in all directions, expanding in balloon like fashion from the source of the sound. If the waves happen to reach someone's ear, they set up vibrations that are perceived as sound.
Sound then depends on three things. There must be (1) a vibrating source to set up sound waves; (2) a medium such as air to carry the waves; and (3) a receiver to detect them.
Noise is defined as unwanted sound, a definition that includes both the psychological and physical nature of the sound. The term "sound" and "noise" are often interchangeable.
HOW SOUND IS PRODUCED AND CARRIED
It is easy to detect the vibrations of many sources of sound. A radio loudspeaker, for example, vibrates strongly, especially when the volume is turned up. If you lightly touch the speaker cone, you can feel its vibrations as a kind of tickling sensation in your fingertips.
Sound waves are often compared with water waves but are actually a very different sort of wave. What they are can be seen by considering what happens when an object vibrated in the air. Suppose someone strikes a gong, as the gong vibrates, it bends outward and inward very rapidly. This movement pushes and pulls at the air next to the surface of the metal. Air is made up of tiny molecules, and when the metal gong bends inward and outward, it creates a wave. The wave travels outward from the gong, becoming weaker and weaker until it dies away.
THE SPEED OF SOUND
Sound waves travel at a constant speed, regardless of the loudness or softness of a sound. Temperature, however, does affect their speed. At room temperature sound travels in air at a speed of 1,130 feet per second. Sound waves travel one mile in about five seconds. At freezing (0o C), sound waves travel at 1,087 feet per second or one mile in about 5 seconds.
Some sounds are high and others are low; some are loud and others barely audible; some are pleasant and others harsh. The three basic properties of any pure sound are its pitch, its intensity, and its quality.
THE PITCH OF SOUNDS
Pitch is simply the rate at which vibrations are produced. Another way to define the pitch of a tone is to find its wavelength. The wavelength of a particular tone is equal to the velocity of sound divided by the frequency of the tone.
INTENSITY AND TONE QUALITY
The intensity of a sound has nothing to do with its pitch. Intensity depends upon the strength of the vibrations producing the sound. The loudness of sounds is measured in decibels (dB).
REFLECTING AND FORCING SOUND WAVES
Like light waves, sound waves can be reflected and focused. An echo is simply a reflection of sound. A flat surface, like that of a cliff or wall, reflects sound better than an irregular surface, like a tree, which tends to break up sound waves.
Other examples of decibel levels are as follows:
| 75-Piece Orchestra - | 130 |
| Car Horn, Snowblower - | 110 |
| Blow-dryer, Diesel truck - | 100 |
| Electric Shaver, Lawn Mower - | 85 |
| Garbage Disposal, Vacuum - | 80 |
| Alarm Clock, City Traffic - | 70 |
| Dishwasher - | 60 |
| Leaves Rustling, Refrigerator - | 40 |
COMPARING SOUND EMISSIONS BETWEEN OTHER ROAD VEHICLES AND SNOWMOBILES
In a paper written Greg Davis and Neil Marietta of Michigan Technological University, tests were performed comparing sound emissions of production trail-ridden snowmobiles to that of other everyday vehicles that travel by road such as passenger cars, motorcycles and semi tractor/trailers. The tests show in many cases, snowmobiles are noticeably quieter. A snowmobile under full throttle emits the same sound level as a truck pulling a camper or an off-road Jeep traveling at constant highway speeds applying very little throttle. So if you refer to a worst case scenario, a snowmobile leaving a stop sign and applying full throttle, the noise produced is still about the same as a very common vehicle simply cruising down the road.
Now, if we look at the worst case scenario in the opposite sense, some motorcycles accelerating and applying nearly full throttle produces nearly 6 times the noise to your ear that a snowmobile driving the same way produces. In a more common example, a logging truck pulling a loaded trailer down the highway traveling at 45 mph will produce twice the noise of a snowmobile applying full throttle. A 4X4 pickup truck pulling a boat on a trailer at a constant speed makes more noise than a snowmobile. Other vehicles have been tested and noted in the paper.
|
Safe Riders! Information
