Each year the NAS receives many complaints about noise from wind turbines.
The noise and penetrating sound of the rotating blades has been compared to the low thud of base notes from loud music or the sound of a constant helicopter at a distance. While there remains dispute regarding the source and definition of this sound, there is no doubt that residents remain disturbed and distressed by its promulgation.
A group of turbines produce pulses of sound which cause greater effect when they synchronise. The sound then resembles distant pile-driving, or as one resident put it, “an endless train”. The turbine sound acquires a distinct ‘beating’ character, the rhythm of which is in agreement with the blade passing frequency and this effect is stronger for more modern, taller wind turbines.
Felt as much as heard
A family living near a wind farm in Askam, Cumbria (7 turbines, 62.5m tall) describe the noise as ‘a washing machine that’s gone wrong. Its whooshing drumming just goes on and on, it’s torture’ and ‘it is an audio version of Chinese Water Torture. The noise is such that it is felt as much as heard’.
So far there has been no success in reducing this invasive noise, caused by wind turbines, which can continue unabated day and night for extended periods and can travel several miles. There are recognised health problems such as pulse irregularity and sleep disturbance associated with this type of low-frequency sound.
Low Frequency Noise and Infrasound
Wind energy developers measure the audible range of noise, but not the lower frequencies – which are sometimes below audible limits. In 2004, the DTI commissioned the Hayes McKenzie Partnership to report on claims that LFN and infrasound were causing health effects. Their report noted that a phenomenon known as Aerodynamic Modulation was occurring in ways not anticipated by UK regulations relating to wind farms ETSU-R-97 (ETSU).
Research by Dr. Amanda Harry showed that all but one of the fourteen people living near Bears Down wind farm in Cornwall had experienced increased incidents of headaches, migraines, nausea, dizziness, palpitations, tinnitus, sleep disorders, stress anxiety and depression.
Wind turbines are now being built to a greater height and blade span than when the original environmental assessments were made for smaller turbines. It is in anticipation of such changes that ETSU guidance itself called for its own review. Unsurprisingly, therefore, recent research studies have highlighted previously unidentified problems.
Professor Peter Styles, Keele University, in the UK, published a study on vibrations from the 60m high wind turbines at Dun Law, Scotland. He found that ‘… when the windfarm starts to generate, even at low wind speeds, considerable infrasound signals can be detected at all stations out to circa 10Km’ and ‘… we have clearly shown that wind turbines generate low frequency sound and acoustic signals which can be detected at considerable distances (many kilometres) from wind farms on infrasound detectors and on low-frequency microphones’.
Whilst earlier studies conclude that there was no significant risk to human health from vibrations produced by wind farms, these studies are dated, and refer to older, much smaller turbines. Concern has increased as most modern wind turbines are in excess of 100 metres high, (much bigger than those at Dun Law). Some developers are proposing to install these devices as close as 650 metres to human habitation and, in some cases, closer. (Ref 1)
While it is noted in the report that turbines should be placed at least 10Km away from any resident, it must also be stressed that acoustic signals relative to distance and disturbance of residents and siting of wind turbines must be reviewed on a case by case basis.
There are other objections to the turbines, especially now that they are being built on a larger scale. The Seamer & Hilton Windfarm Action Group in the northeast of England published a report in January 2009 describing many of the risks to the general public from wind turbines including noise, light flicker, and accidents involving giant turbines catching fire, shedding blades or parts of blades and throwing large ice lumps.
Again, such issues call into question the suitability of ETSU regulations and support the many calls for their urgent review.
The economic argument proves that wind power generated energy is one of the most expensive forms of electricity and survives on direct and indirect subsidies bringing an added cost to tax payers without making a significant contribution to reducing greenhouse gas emissions.
Wind turbines built on peat-lands (which represent substantial long term stores of carbon which is released if they are disturbed) are therefore counter-productive as they will then release CO2 into the atmosphere throughout the life of that wind farm. (Ref 2)
The strobe effect from wind turbines, when the sun is behind the rotating blades, can cause dizziness, headaches and trigger seizures. Shadow flicker and reflected light from blades can also cause problems. These light disturbances are experienced inside the home as well as outside.
In April 2005, the BBC reported that the owners of a wind turbine near a top security prison (Whitmore Prison in Cambridgeshire, England) agreed to turn the turbine off in the early mornings to prevent possible ‘security problems’ because prisoners were becoming upset by the flickering shadows.
Hazardous to wildlife, bats and birds
Julia Armstrong, Conservation Officer and wild life trust co-ordinator for Berkshire, Buckinghamshire and Oxford in the UK states that “Wind turbines are a potential hazard for bats. Bats use echolocation to build up a picture of their surroundings but cannot detect the rotating blades or changes in air pressure around the blades. This leads to collision with the blades causing fatalities and internal injuries caused by the pressure changes. Most research has been conducted in the USA and Europe, and the siting of turbines is therefore an issue for bats in the UK.”
Out of date regulation
Doubts are shared by many acousticians with regard to the continued usefulness of current UK noise regulations relating to wind turbines, ETSU-R-97, which are now some ten years old and refer to a previous generation of much smaller turbines.
The current method of calculating noise from a wind turbine is not able to predict noise levels accurately. A range of factors affect the possible noise pollution: the turbine design, atmosphere, wind speed, terrain, time of day, all of which cannot be contained within even the most complicated algorithm.
A study carried out on a 30MW, 17 turbine wind farm on the German/Dutch border showed that ’there is a distinct audible difference between the night and daytime wind turbine sound’. (Ref 3)
The study found that night time wind speeds were some 2.6 times the expected levels calculated which resulted in sound levels from turbines some 15dB higher than the predicted emissions.
The national calculation models used measured wind speeds at a height of 10m, however, at a hub some 58m above the ground, they were up to 18dB noisier than the calculated value suggested.
New research required
In order to protect the public, the Noise Abatement Society would like to see this problem addressed by government, urgently, through the commissioning of further research into the multiple health and environmental effects caused by wind turbines and the amendment of ETSU-R-97 regulations.
While the Society commends generation of renewable energy through natural resources, this must not come at the price of extreme disturbance and health risks to residents. To this end, we intend to help motivate government to review its current regulations.
- D. M. J. P. Manley. P. Styles and J. Scott ‘Perception of the Public of Low Frequency Noise’. Journal of Low Frequency Noise, Vibration and Active Control, Vol. 21 No1 2002
- R. A. Lindsay and O. M. Bragg, Wind farms and Blanket peat. University of East London 2004
- G.P. Van Den Berg ‘Effects of the wind profile at night on wind turbine sound’ Journal of Sound and Vibration Vol. 244 2004