Are Snowmobiles Sound Pollution?
Do they really hurt the environment?Sound and the Environment
Sound
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 Snowmobiles 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.Understanding the Basics of
Sound/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
is 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 the air
at a speed of 1,130 feet per second. Sound waves travel one mile in
about five seconds. At freezing (0 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 are 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:
Sound dB(A)
75-Piece Orchestra
130
Car Horn, Snowblower
110
Blow-dryer, Diesel Truck
100
Electric Saver, Lawn Mower
85
Garbage Disposal, Vacuum
80
Alarm Clock, City Traffic
70
Dishwasher
60
Leaves Rustling, Refrigerator
40
Effects on Wildlife
Dr. Andres Soom participated in the University of
Wisconsin's comprehensive three-year study on the effects of
snowmobile sound levels on deer and cottontail rabbits. His report
entitled Emission, Propagation and Environmental Impact of Noise
from Snowmobile Operations, concluded that "only minor reactions
were noted in the movements of cottontail rabbits and white tailed
deer to moderate and intensive snowmobiling activity". He stated
that it had not been possible to determine sound levels at which
there is clear reaction on the part of the deer "because
snowmobiles must be so close to deer to generate the higher levels
that other factors such as visible presence…are likely to be
more important".
The Wisconsin study also
compared the reaction of deer to the presence of cross-country
skiers. When cross-country skiers replaced snowmobiles on the test
trail systems, the deer moved away from the trail more
frequently.
A three-year study, Response of
white-tailed Deer to Snowmobiles and Snowmobile Trails in Maine,
conducted by wildlife scientists for the Maine Cooperative Wildlife
Research Unit and the Maine Department of Inland Fisheries and
Wildlife, revealed that:
"Deer consistently bedded near snowmobile trails and fed along them
even when those trails were used for snowmobiling several times
daily. In addition, fresh deer tracks were repeatedly observed on
snowmobile trails shortly after machines had passed by, indicating
that deer were not driven from the vicinity of these trails…
The reaction of deer to a man walking differed markedly from their
reaction to a man on a snowmobile… This decided tendency of
deer to run with the approach of a human on foot, in contrast to
their tendency to stay in sight when approached by a snowmobiler,
suggests that the deer responded to the machine and not to the
person riding it".
In a study entitled Snow
Machine Use and Deer in Rob Brook, conducted by the Forest Wildlife
Biologist of the White Mountain National Forest in New Hampshire,
snowmobile operations and deer movement were monitored. A summary
of the study indicated that deer travel patterns were not affected
by periodically heavy snowmobile use. In addition, continued use of
established trails was recommended.
The
University of Minnesota issued a study by Michael J. Dorrance
entitled Effects of Snowmobiles on White Tailed Deer which found no
meaningful difference in the deer's home range during periods of
snowmobile use and non-use.
Addressing the
subject of snowmobile operations in Yellowstone National Park, Jack
Anderson, a former Superintendent of Yellowstone commented:
"We found that elk, bison, moose, even the fawns, wouldn't move
away unless a machine was stopped and a person started walking. As
long as you stayed on the machine and the machine was running, they
never paid any attention. If you stopped the machine, got off and
started moving, that was a different story. The thing that seemed
to be disturbing to them was a man walking on foot".Effects on People
Operated in normal, considerate manner, snowmobiles are barely
audible from inside a home. From a distance of 50 feet, snowmobiles
generate between 68 - 73 dB(A) at 15 mph. Since doors and windows
are almost always closed in the winter, snowmobiles operating
outside at a distance of 50 feet only create an interior sound
level of between 41 and 47 dB(A). From a distance of 200 feet,
snowmobiles produce an interior sound level between 29 and 35
dB(A). This is well below the average evening household sound level
of 47 dB(A).
Dr. Andres Soom, concluded
from his study that the newer, quieter machines can travel within
45 feet of a residence without adverse effect.
Natural sound barriers, careful trail planning and reduced
speed limits in residential areas further reduce snowmobile noise.
Snowbanks or trees can cause a 20 dB drop in sound levels if they
are between the machine and listener. Government and enforcement
officials report they now receive few if any complaints from
citizens about snowmobile noise.
U.S.
Forest Service researcher Robin Harrison, reported that under usual
wildland conditions, snowmobile operation is undetectable to the
human ear at distances of more than 750 feet. He reported that
snowmobiles were barely detectable above normal campground sound
levels at a distance of 400 feet.Compaction and Vegetation
Everything we do has some effect on the environment. When a
hiker steps on a flower, he affects the environment. When land is
paved over for a bicycle path, it effects the environment. Many of
the foot paths man has used for centuries still exist and are
clearly visible throughout the world.
However, it' a fact that a snowmobile and rider exert
dramatically less pressure on the earth's surface than other
recreational activities (i.e., just one-tenth the pressure of a
hiker and one-sixteenth the pressure of a horseback rider). Average
pounds of pressure per square inch exerted on earth's
surface:
Object
Pounds Of
Pressure
Four-Wheel Drive
Vehicle
30
Horse
8
Man
5
All-Terrain Vehicle
1.5
Snowmobile
0.5
(All vehicle weights considered
include 210 pounds estimated weight of one person and
gear).
Moreover, the snowmobile's
½ pound of pressure is further reduced by an intervening
blanket of snow.
In many
jurisdictions, snowmobiles are not classified as off-road vehicles.
By both definition and management policies, these jurisdictions
have been completely separated snowmobiles from off-road vehicles.
As the U.S. Department of the Interior concluded in an
environmental statement: "A major distinction is warranted between
snowmobiles and other types of off-road vehicles. Snowmobiles
operated on an adequate snow cover have little effect on soils -
and hence cause less severe indirect impacts on air and water
quality, and on soil-dependent biotic communities, than other ORV's
do".
Given adequate snowfall and
responsible operation, all evidence of snowmobile operation
disappears when the season changes and the snow melts.
In its environmental statement regarding off-road
vehicle use of public lands, the U.S. Department of Interior
stated: "Where snowmobiles are used exclusively over snow on roads
and trails, the impact on vegetation is indeed virtually
nil".
A University of Wisconsin study of J.
W. Pendleton entitled Effect of Snowmobile Traffic on Non-Forest
Vegetation discovered that snowmobile traffic had no effect on
grain yield of winter wheat, alfalfa, red clover plots or grass
legume. Species of turf grass showed slightly reduced yields at
first harvest, but were not negatively affected in subsequent
harvests.
Research undertaken by Dr. James
C. Wittaker and Dennis S. Wentworth of the University of Maine
concluded that "compaction by snowmobiling does not alter the grain
weight yields of alfalfa in Maine".
A Utah
Water Resource laboratory study found that snow compaction, caused
by snowmobile tracks, does not damage wheat crops. Instead, the
compaction increases the yield and eliminates snow mold. Erosion is
also reduced.
There is no evidence that
snow compaction caused by snowmobiling, ski-touring or snowshoeing
has a significant impact on the population as small burrowing
animals. Since these recreations take place over a minuscule
portion of the total land area, the ecosystem of burrowing animals
tend to be overwhelmingly affected by natural forces-such as
wind-induced compaction, early and late snowfalls, temperature
fluctuations resulting in thaws and freezes, etc.
Article originally posted on the American Council
of Snowmobile Associations (ACSA) web site at www.snowmobileacsa.org Text has been modified for
publication on this site with permission of the ACSA.
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