Wind Turbines Generate Electricity and Controversy: a series on whats in the wind.
There is a small but growing number of citizens that detest the increase in wind farms across Australia, Canada, Europe and the United States. Their goal is ostensibly to protect residents by banning new wind turbines from being built and site the cumulative negative impacts on animals, people and the environment as justification. Eric Rosenbloom of wind-watch.org sums up the complaint this way “It’s well past time to stop considering what wind might do and to examine what it has done. It has not reduced fossil fuel use or emissions. It has only ruined a lot of landscape and communities, fragmented habitat and killed birds and bats”.
Opponents objections and concerns regarding wind turbines can be listed in eight distinct categories: Visual, Noise, Intermittent Power, Birds/Bats death, Altering Vegetation, Fire, Ice and Pollutants. In this first article, Wind Farms – Cons, Part 1 the discussion is wind turbine noise.
There are two aspects of the wind t. noise complaints, audible sounds and inaudible sounds. Humans have a hearing range from a frequency of 20 Hertz to 20 kilo Hertz, that is audible sound. Some animals such as bats and dogs can hear sounds beyond that range but for humans those frequencies are inaudible. Sound moves in waves of pressure. It vibrates the ear drum, it moves through air or water, gas and elastic solids. The power or intensity of that wave is the magnitude, measured in decibels (dB) which relates to the volume or loudness. The other component of sound is frequency. That frequency with a high number has a tightly spaced repetitious wave pattern of compressions. A low frequency sound has compression waves spaced further apart. Drums or bass are types of low frequency sounds. Sub-aural low frequency vibrations is one of the complaints about wind t. noise. Some individuals claim a higher sensitivity than others and the inaudible sounds created by turbines purportedly cause them anxiety and other noise related symptoms.
Opponents of wind turbines say the audible noise affects animals, lowers property values, causes suffering and is a serious risk to health. Several doctors have noted a marked increase in depression for some people living near wind farms. Medical journals recognize a wide range of symptoms associated with noise that affect health.
Noise symptoms: poor concentration, anxiety, emotional stress, nervous complaints, nausea, headache and instability. Symptoms may also include a weakened immune system, sexual impotency, argumentative mood, social conflicts, panic attack, neurosis, psychosis and hysteria.
Clearly wind t. noise is a threat to society and communities everywhere. Nobody wants to see a bunch of unstable hysterical people running around a wind farm in an argumentative emotional mood being nauseous.
Wind turbine noise syndrome is a con. The power of suggestion conveyed by various media might have much to do with the anticipatory audio experience of wind turbines. Nina Pierpont a pediatrician in Malone, New York coined the term Wind Turbine Syndrome in a book she self published in 2009. Since that time her theory (promoted and distributed by her husband Calvin Luther Martin) of health related issues from exposure to wind turbines has been used by anti wind farm activists to foster fear and alarm. Fact is Nina Pierpont’s studies are flawed. Bad science may generate news headlines and used as a banner justifying a cause, but in the end if it is not supported by expert peer review it is still bad science.
Simon Chapman, a professor of public health at Sydney University, has said that wind turbine syndrome is not recognized by any international disease classification system and does not appear in any title or abstract in the massive US National Library of Medicine’s PubMed database. He says the term appears to be spread by the vector of anti-wind farm activists.
The publication Wind Turbine Sound and Health Effects- An Expert Panel Review 2009 is an extensive analytical review of a large body of peer reviewed literature on sound and health effects in general and on sound produced by wind turbines. The conclusions by this expert panel are: There is no evidence that audible or sub-audible sounds emitted by wind turbines have any direct adverse physiological effects. The ground-borne vibrations from wind farms are too weak to be detected by, or to affect, humans. The sounds emitted by wind turbines are not unique. There is no reason to believe, based on the levels and frequencies of the sounds and the panel’s experience with sound exposure in occupational settings, that the sounds from wind turbines could plausibly have direct adverse health consequences.
The British Acoustics Bulletin published in 2011 their 10th independent review of the evidence that wind farms are causing annoyance and ill health in people. For the 10th time it has emphasized that “annoyance has far more to do with social and psychological factors in those complaining than any direct effect from sound or inaudible infrasound emanating from wind turbines”.
What about the whooshing? Wind turbines can and do produce sounds. There is the first type which is produced by moving mechanical parts (gear box, electrical generator, bearings, etc.). Modern turbines are already extremely quiet and engineers continue to make technological advances using new materials and other improvements at the design stage such as incorporating acoustic insulation for the turbine housing. Another example of innovation is the direct drive turbine. These machines have no gear box or drive train and no high speed mechanical components. The second type is aerodynamic sound, caused by the revolutions of the blades passing through the air – the whooshing. The blades of a wind turbine are designed like any other wind foil to create lift. The same principle as an aircraft wing. The wind passing over the leading edge of the blade will start the movement and thus rotation. The speed of blade rotation is in direct proportion to the speed of the wind. The sound made during the rotation is also in proportion to the wind speed and the blowing wind actually masks most sounds of blade aerodynamics, more so if the wind moves through trees, corn stalks etc. One innovation being researched is a saw tooth design at the trailing edge of the blade. The concept is to mimic a birds feather such as an owl which is known for silent flight.
On the decibel scale the smallest audible sound the human ear can detect is near 0 dB. A sound 10 x more powerful is 10 dB. A sound 100 x more powerful than near total silence is 20 dB. A sound 1,000 x more powerful than near total silence is 30 dB. A Jet Engine at takeoff is 1,000,000,000,000 x more powerful than 0 dB. Here are some common everyday sound levels.
- 170 dB – Shotgun
- 140 dB – jet engine at takeoff
- 120 dB – Ambulance siren
- 110 dB – Chainsaw/Car horn/Symphony Concert
- 96 dB – Tractor/Motorcycle
- 90 dB – Subway/ power lawn mower
- 70 dB – Alarm Clock/Ringing Telephone/Flush Toilet
- 60 dB – Normal conversation/ Hair Dryer/Vacuum Cleaner
- 50 dB – Electric Shaver/Dishwasher/Refrigerator
- 40 dB – Quiet room
- 30 dB – Whisper in ear
- 30 to 55 dB are regulated limits for wind farms in most countries.
The Canadian Centre for Occupational Health and Safety has required that at a distance of 350 meters outside, a wind energy project would have a noise level between 35 and 45 dB. In Sweden sound pressure level for noise from wind turbines is 40 dB near dwellings. Denmark has a limit outside dwellings of 45 dB and for sensitive wild areas 40 dB. French legislation specifies an emergence of 3 dB over background noise at night and 5 dB over background noise daytime. Great Britain also considers background noise and population density in calculations but wind farm noise should be limited to an absolute level within the range of 35-40 dB. In the U.S. individual states and counties regulate wind farm noise standards and guidelines. These regulations vary in limits from a 55 db daytime to an extremely low 30 dB in Whatcom County in Washington. Most states and counties are well within the range of World Health Organization recommendations for any type disturbing evening noise to be limited to 40 dB.
The Bottom Line. Wind turbine syndrome is a con. A few individuals are annoyed by having wind farms built in their community but annoyance is not the same as a health concern. The 161st Meeting Lay Language Papers of the Acoustical Society of America published May 23, 2011 sums it up nicely: ” Wind power is one of America’s fastest-growing renewable energy sources. Part of the problem is that wind farms are often located in rural areas that typically have low existing sound levels. Consequently, the moderate noise produced by the turbines becomes more prominent. Such impacts on nearby residents can be minimized through proper planning and siting. “