Sound

Hearing is an amazing sense that we all take for granted. As human beings we live in a world of sound, some natural and other manmade. Some sounds are comfortable, restful, interesting, and pleasing. Others are disquieting, annoying, distracting, and bothersome. In deciding whether a sound is a normal part of life or constitutes intrusive noise we unconsciously take several factors into account:

Loudness

The intensity of sound or sound pressure level (SPL) is measured in decibels (dBA). SPL measurements are taken with respect to the minimum threshold for human hearing. A 20 dBA difference in SPL represents a ratio of ten-to-one in sound pressure. Thus, 40 dBA would be a sound pressure level that is 100 times greater than the sound pressure level of the quietest sound that normal human hearing can detect.

To give you an idea of how dBA measurements relate to daily life, a listing of the approximate sound pressure level for various sounds is provided below. Here's a chart adapted from Wikipedia and other sources:

dBA

Source (with distance)

140
Rifle being fired at 3 feet

120
Threshold of pain; train horn at 30 feet

110
Accelerating motorcycle at 15 feet; chainsaw at 3 feet

100
Jackhammer at 6 feet; jet engine at 750 feet

90
Loud factory; heavy truck at 3 feet

80
Vacuum cleaner at 3 feet; curbside of busy street

70
Busy traffic at 15 feet

60
Busy office

50
Restaurant inside

40
Residential area at night

30
Theater, no talking

20
Quiet country area at night

10
Human breathing at 9 feet

0
Threshold of human hearing; mosquito at 9 feet

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.

Position

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.

Aging 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 out?

The Wind Direction

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.

Some Final Questions

Here are a few other questions to ponder while sitting on your porch in the country:

How 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 50 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?