Wind Turbine Troubles By Dr. Jimmy Tragle, Part IIIB

Part III B

As mentioned previously, noise pollution is a big issue and deserves a lot more attention than industry proponents wish to give it. This is perhaps one of the biggest areas of potential harm for onshore turbines and may be an issue for offshore ones. I've yet to see convincing evidence that offshore noise won't be a problem for some species. This is an area I've devoted very little time to. I'll limit my comments to the fact that whales can communicate for distances up to 1500 miles using low frequency sounds. Shipping already hampers this. Low frequency sounds from turbines may have some issue here. I think I mentioned a lack of scientific evidence in a previous section. The importance of that notion is that there is a lack of evidence to claim anything. So, do we charge ahead and make a mistake or use the existing turbine facilities to figure out potential troubles. This is an area of study left best to truly unbiased groups with some distance from the turbine debate. Of note is that most offshore installations are in shallow waters and there is a push to put them in deeper waters. Sound behavior is different for those differing depths and floor topography. That much is known.

I have been very interested in noise pollution from land based turbines. This is an area filled with discrepancy. From my own personal experiences I've every reason to believe that the industry understates this with bold intent. On the farm that I own we can hear spring peeps in a pond that is about 330 feet from an old farm house that is perfectly livable. We can also hear passing cars and their radios from a cemetery on the property. The road we hear them on is a little over 1/2 mile away. It is important to note that this is a very rural community. I've yet to hear a rolling boom box playing rap music. Not that I'm having a dig at that sort of music, but anyone that has heard a car going down the road with a sub woofer kicking out music knows why I'm pointing this out.

The point is we can hear cars with OEM exhaust systems tooling down a road where speeds seldom exceed 30 mph from 1/2 mile away. For comparison a car running down a highway is claimed for reference to be about 55 dB at 100 feet I believe. So if background noise was at 50 dB in the vicinity of where you are standing you absolutely would not hear a car going 30 mph down a country road 1/2 mile away. The company that wants to develop the ridge claims background levels of sound to be 50 dB. Clearly that is not consistent with my own experiences in this rural location. Reality and honesty suggests a background level of noise in the 20 to 30 dB range, probably closer to 20 dB.

To top off this claim the developer contends that the noise from the turbines will rapidly fall below 50 dB. Levels are around 100 + dB at the turbine. This is used to assert that noise is not an issue for neighbors of wind plants. This couldn't be any further from reality.

It is at this point where a discussion of atmospheric conditions and their influence on sound propagation is in order.

Firstly atmospheric conditions are not a constant that a single mathematical formula can be generated about to make predictions for sound propagations. The models used by industry fail to take this into account and it is reflected, once again, by reality at existing wind plant sites.

Understanding the differing conditions is not all that difficult in spite of the fact that understanding concepts and mathematical formulas surrounding sound propagation are beyond the scope of the average human being. That doesn't imply stupidity, this stuff is really complex.

What may be simple to understand is that day and night atmospheres differ vastly. During the daytime the sun heats the earth's surface and causes rising air currents. Buzzards and glider pilots use these thermals to drift effortlessly through the sky. Think of them as wind moving vertically. With their influence winds traveling parallel to the ground are dampened or impeded.

The winds at ground level will vary little from winds at say 300 or 400 feet above the earth's surface. There will also be wind speed differences if you look at various locations on the ground. You may have a wind moving 20 mph in one place and in a place 500 feet away it will only be going 10 mph. This is known as an unstable atmosphere. It is due to the layering of air temperature where the bottom is warmest and the top layers are coolest. Warm air rises and the ability for wind speeds to vary in one layer compared to another are limited. Think of the wind being in layers as in a cake.

Take away the sun as night fall does. Eventually the earth's warm surface cools and you end up with the warmer air at the top and the cooler air at the bottom. As one moves higher above the earth's surface wind speeds can vary significantly. Below 50 or 100 feet you may have absolute calm. Above these heights you may have strong winds. Now consider that the air doesn't necessarily blow in the same direction as one moves up away from the ground. Think of that layer cake as being a stack of pieces of wood with their grains being at slight angles to each other indicating not only differing wind speed but different angles with respect to a line drawn on the ground. This is known as a stable atmosphere. There is a temperature gradient with warm air at the top and cool air at the bottom. No vertical movement occurs so no damping of horizontal movement occurs. Wind speed at given layer is more apt to be a constant. The variations occurring as one moves up to the next layer. This is a stable atmosphere.

The third possibility is a neutral atmosphere and exists in the absence of a temperature gradient.Actually there is a classification system for atmospheric stability that is a numbered gradient form unstable to stable. But the above simplification serves to explain.

The stable atmosphere can also serve to reflect sounds back downward. This creates an interesting phenomenon where one can detect very little sound right up under a turbine, but some distance away it can be quite loud.

The take home message here is that the most noise occurs at night when people are trying to sleep. There is little to no background noise at ground level as there is little to no wind. At hub height the winds are often great enough for maximum output for the turbines. This has some rather adverse consequences. It is also notable that a room such as a bedroom can serve to amplify sounds, especially low frequency sounds. I've witnessed this in my practice. I can hear heartbeats of animals in cages if I stick my head inside the cage. I'm not using a stethoscope and I have normal hearing. Maybe mine is a bit better than the average person as my employees might tell you. My wife might disagree though.

There are several sources for sounds in the turbines. Sources of noise include drive gears between the turbine's hub and the generator, the gears that rotate the nacelle so the turbine is in the wind properly, and the generator produces noise as it spins (these are the equivalent to giant electric motors - if you've handled small electric motors you know they produce noise). These noises may be sheltered by the nacelle shrouding them.

The blades themselves are a source of noise as they slice through the air. The type of turbine has some influence over this. Industry claims the newer turbines are quiet because of blade design and the fact that the turbines are now upwind type. Meaning the blade sees the wind first. On downwind blades there is a thump as the blade goes by the tower. It is due to the air being relatively still behind the tower so there is an abrupt change of conditions surrounding the blade as it goes by the tower. THUMP! There is still a thump generated by an upwind turbine. It isn't as prominent, but it is still present. Some turbines situate the rotational axis so blades are not parallel to the tower but slope away from it. There is still a thump.

Recall that wind speeds at night are steady for each layer in a stable atmosphere. That means the turbines will all be turning at the same speed as opposed to a variety of speeds as one may expect during the day. Blade pitch can be varied to find tune speed according to available wind, but the turbines are likely to turn synchronously at night. That puts the blade sounds in phase with each other. Think of 44 cars traveling at regular intervals with the same rap tune being played through the same model sub woofer all in synch with each other.

The thump as the blade passes the tower produces a pressure pulse between the blade and tower. That pressure pulse creates an earth vibration via the tower and its foundation. If the turbines at a given site are turning at the same speeds these vibrations can be synchronous with each other. If synchronous the vibrations will have coherence.

Coherence means the vibrations will be added together to increase the strength of the vibrations. Simply put, one person cannot push a large truck, but several can because collectively the group is stronger than each individual is alone. Coherence at turbine sites has received no attention from industry at this point. It is receiving attention by other groups currently, but nothing has been published.

Terrain can influence sound traveling over land (or water). Steep slopes can strongly reflect the sounds giving additive effects further down slope. Snow covered ground will also enhance the sound.

It is at this point that I'd like to inform you that the sound predictions made by industry experts prior to construction use models that don't account for stable atmospheres. More importantly is the fact that measurements made by individuals suffering the consequences more neatly match the sound predictions made in consideration of stable atmospheric conditions. In short, reality differs with industry claims made prior to construction during the permitting phase.

When one thinks of sound the concept is usually restricted to things you can hear. Sound can exist in frequencies above and below the range humans can hear. That doesn't mean they are beyond sensation. Low frequency sounds will have a tactile quality. That is to say you can feel them. If you have ever been sitting at a rail crossing and had a diesel locomotive roll by at a low speed you've experienced this type of noise. You feel as well as hear the sound. The sensation resonates through your entire body.

I have to relay my own personal experiences from a recent visit to a wind plant. Keeping in mind the time the sound is at its worst I took a trip to Thomas, West Virginia in Tucker County. This is near the location for a wind plant on the ridge of Backbone Mountain. Route 32 goes through Thomas and intersects Route 219. If you turn south on 219 and go about 4 miles you will come upon Sugarlands Road on the right hand side. Turning right on Sugarlands you will immediately see a gravel parking area on your right. Before you see any of this you will notice the massive turbines if you go during the light of day. I arrived about 5 a.m. under rather harsh conditions. It was very windy yet I could still hear the whoosh of the blades. This was a rhythmic sound occurring in relation to the blade speed, about 18 rpm. About 1 whoosh per second. At some times it was rather astounding, almost sounding like meat searing on a grill. This was quite close to the turbines. I think a bit too close considering the blade and ice throw comments earlier. I'd be surprised if I was more than 1000 feet from the base. I'm of the mind that it was probably much closer.

Alternatively you can head north on 219 from 32 again about 4 miles and you encounter the turbines again further north on the ridge. I did just this and decided to continue north to see if I'd encounter more turbines. I continued for another 4 miles down the ridge away from this point. This was downwind from the turbines. This section of West Virginia has roads that are more rolling rather than switch backs. Four miles by road was quite a substantial distance from the turbines as well.

I noticed something that I hadn't expected after I turned around to go back over the ridge. It was just beginning to become light out at this point. When I was about two miles from the ridge, by road, I noticed a rhythmic vibration that completely enveloped me and it seemed to be following the same beat as the whooshing mentioned at the first encounter. I couldn't so much hear it as feel it throughout my body. I developed a pounding headache followed by nausea. A tingling sensation developed in my hands. I also had an odd sense of disorientation (not quite dizzy, but a similar feeling). The best way I can describe it is to compare it to the feeling you get on a commercial jet on take off when the plane goes into a steep climb, most evident if you fly at night. Your spatial sensations are confused as you only see what is going on in the cabin yet feel the acceleration in your vestibular apparatus. The vibrations seemed to be most intense when I put the engine under mild load on the uphill sections of the road and I could readily call this up by manipulating the throttle. I thought it may have been a character of the engine I'd never picked up on so I made a point of paying attention to the sensation taking in all detail.

I crested the ridge and kept on going on the upwind side of the turbines. Mountain roads tend to undulate up and down hill whether you're going toward the top or the base of a mountain, so I had plenty of uphill grades to load the engine. What I noticed was the vibration was still present but much less intense. I went on through Thomas and continued south on 32 paying attention to the uphill areas. I could no longer get the sensation to occur after putting a few miles between me and the turbines. First the tingling and disorientation disappeared and then the headache. The nausea lingered for an additional hour.

Coincidentally numbness, nausea, headaches, and dizziness are commonly reported by people living in the shadow of wind turbines. Industry likes to write these folks off as complainers. On my own behalf I'm not one to run to the doctor for every little hangnail. I've only been to an ER for two fairly severe dog bites - one severed nerve, artery, and vein and one puncture to the hand that my receptionist had to nag me to get me to go to the ER. About two years ago I ruptured my spleen after losing an argument with the ground - I foolishly didn't seek medical help for over twelve hours. I think my symptoms in Tucker County were real.

I'd like to repeat that the models used by the industry to predict sound do not give the same results as models used by other researchers. Measured sounds taken from properties where people experience problems reflect the stable atmosphere predictions made by non-industry scientists. Industry maintains sounds won't be an issue beyond 1000 feet or so. People 2 miles away suffer the impacts described above. Interestingly enough the web site for a turbine manufacturer in Europe recommends a 2 km setback minimum. I contacted them to find out their reason for this policy and received no reply. It has also been suggested that setbacks for turbines in mountainous regions may need to be greater than those on level lands.