Interestingly, our perception of loudness is not the same as sound
pressure level. Although the actual formulas are somewhat complex,
as a rough rule of thumb, an increase of 10 dBA is perceived to be
approximately twice as loud. Thus a 20 dBA gain would seem to be about
4 times as loud, and a 40 dBA gain would seem to be about 16 times as loud.
If a sound is louder than the background level, it
will stand out and be noticed and, if it is unpleasant, it will be perceived as noise. While
the noise generated by wind turbines will be masked to some degree by
surrounding ambient sounds, which are higher when the wind is up, and can
be ignored by most people during the daytime, it is at night when ambient
sounds have quieted down and folks are trying to rest that the noise
effect will be most annoying.
According to documents submitted by UPC Wind, each one of their
bus-sized 2.0 MW wind turbines radiates an average of 105.3 dBA of sound pressure. They quickly point
out that these will be nearly 4 blocks away from any residence and that
the sound level should have dropped down below 50 dBA by then. However, this
is about 20 dBA louder than a quiet night in Cohocton, or 4 times
as loud. Quite
noticeable, in other words.
Remember also that these turbines are designed
to be mounted 250 feet off
the ground where they will be unobstructed by trees or structures of any
kind that could muffle the noise they make. Another little-discussed fact
is that their noise is related to wind
speed, and the wind
is faster up there (that's the advantage of stationing them on high
hilltop towers). Down below, the air may be relatively still and quiet,
while up at turbine height there may be a brisk breeze. Can you imagine 41+
heavy trucks powered up all over the hills, projecting noise from the tops of
towers into the stream of the wind?
Timing - Night and Day
But noise isn't all about loudness. It has to
do with what time of day it is being generated and how repetitive, unnatural, annoying, and incessant the sound is.
Most of us can put up with a lot of extraneous sounds that come and go
during the daytime when we're occupied or making our own noise. But
what about at night when the wind is blowing steadily and the
turbines in our region are most likely to be active? How many times have you been kept awake by a dripping faucet that wouldn't
stop or a twig from a tree tapping against your house? What about a steady
"whup, whup, whup" throbbing 51 times a minute for hours at a
time through the night,
punctuated only by the groaning of the wind around the tower mast, the
mechanical grinding of the nacelle motors as they turn the blades into
the wind, and the screeching of rotor brakes when the wind speed rises
above threshold? Ear plug time. Gone are the quiet nights you once took for granted.
of the Turbines
Does machine noise increase or decrease with
the age of a machine? Is your 10 year-old tractor quieter than the new one
you just bought? How loud will these turbines be 5, 10, 15, or 20 years
Then there's the wind itself. Here's a
question for you. Does sound carry on the wind? It sure does. It
can travel over a mile downwind on a breeze. So when the wind is blowing and the
turbines are churning and the blades are chopping, you can expect the
noise to carry. Do you think it will respect any 1,500 ft boundary? Not on
your life. This noise, broadcast from higher than our hills, will be
seeping night after night into every quiet hollow downwind.
Who is Listening?
How annoying wind turbine noise is perceived
to be is also influenced by what are known as "receptor factors"
like how sensitive a person's hearing is and whether or not they are
supportive of the wind project. It's common knowledge that people
experience a progressive hearing loss as they get older known as
presbycusis, similar to the change in their vision that calls for reading
glasses. Others have been exposed to loud noise and have actually damaged
their hearing. People like this will be less likely to be bothered by wind
turbine noise because they can't hear it, while those whose hearing is
sharper are complaining. It's also a documented
fact that people who are in favor of a wind power project are more
likely to adapt to the noise than those who see it as an unwanted
intrusion on the quiet spaces of their lives.
Here are a few other questions to ponder
while sitting on your porch in the country:
many decibels does an owl make when it hoots across the meadow, or a dog
barking in the valley, or a gaggle of wild geese as they fly overhead, or a
crow as he calls to his buddies? How loud are peepers peeping in the pond,
wild turkeys responding to a call, wind rustling in the trees, or a deer
snorting in the woods? Are your evenings and nights lying in your bed as
loud as an active restaurant is inside?
Cohocton at night is closer to a
sanctuary than a busy street, for now anyway. Cohocton's first Windmill Law,
passed in January 2006 but recently challenged in court, allows turbines to make
dBA of noise at property lines. Its recommended replacement, Windmill Law #2,
specifies 52 dBA. What if
they turn out to be even louder? Who will fix that problem?
J. Alberts "Primer for Addressing Wind Turbine Noise"
"Noise annoyance from wind turbines - a review"
"Wind Turbine Acoustic Noise"
Stewart "Location, Location, Location - Wind Farms and
Van den Berg
"Effects of the wind profile at night on wind turbine sound"
James "Simple guidelines for siting wind turbines to prevent health
UPC Noise Studies
Updates Noise Articles
vanity," says the Preacher, "all is vanity and chasing
after the wind."