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Living only 1400m from the testmast and 850m of a probable turbine, noise is a key issue I am concerned about with having a windfarm in Longhirst. I have written already some comments about noise in the 'Windfarm general: Noise' section of this page and would like to build on this here. First, how much noise can we expect? It is impossible to make acurate predictions without knowing the exact position and type of turbines. Sound is of course affected by wind speed, temperature, humidity, precipitation, the presence of barriers and buildings to name just a few. So the numbers I state here are nothing but an ?educated? guess. I have put the coordinates of turbines as mentioned on the 'Where' page of this website in the 'Wind Turbine noise Model' of the National Physical Laboratory. I have assumed, that RES is not building turbines T2 and T3 (see my comments on the 'Where' page) I have further assumed that all turbines and properties are placed 0m above sea level, the hub of the turbine would be 80m high and the sound power level of the turbine would be 100dB (I have found on several websites that the sound of a single turbine is usually estimated to be in the range of 90 -100dB(A)). It came up with following results:
RES follows the ETSU Noise Working Group Guidelines for noise assessment which is accepted as the standard by planners and developers. This would include the use of 'noise maps' a geographical representation of noise levels similar to a topographical map with contour lines. I understand, that these maps would be part of an Environmental Impact Assessment and would obviously be far more acurate than what I have calculated above. What does this mean ? I have found following table on several websites: (e.g.: Sustainable Development Commission )
So a noise level between 33 and 38 dB in Longhirst would put us in the region of 'Rural night-time background'. With people closest to the windfarm most likely being able to hear it. The Department for Business Enterprise & Regulatory Reform suggests a daytime noise level should be limited to an absolute level within the range of 35-40dBA. So, we would be just in the range. Interesting to note are following facts:
Other types of Noise:
Noise and Health: I refer here to the Guidelines for Community Noise (World Health Organization 1999) Chapter 3.3 Sleep disturbance "The primary sleep disturbance effects are: difficulty in falling asleep (increased sleep latency time); awakenings; and alterations of sleep stages or depth, especially a reduction in the proportion of REM-sleep (REM = rapid eye movement) (Hobson 1989). Other primary physiological effects can also be induced by noise during sleep, including increased blood pressure; increased heart rate; increased finger pulse amplitude; vasoconstriction; changes in respiration; cardiac arrhythmia; and an increase in body movements (cf. Berglund & Lindvall 1995). For each of these physiological effects, both the noise threshold and the noise-response relationships may be different. Different noises may also have different information content and this also could affect physiological threshold and noise-response relationships (Edworthy 1998)." "Questionnaire data indicate the importance of night-time noise on the perception of sleep quality. A recent Japanese investigation was conducted for 3 600 women (20–80 years old) living in eight roadside zones with different road traffic noise. The results showed that four measures of perceived sleep quality (difficulty in falling asleep; waking up during sleep; waking up too early; feelings of sleeplessness one or more days a week) correlated significantly with the average traffic volumes during night-time. An in-depth investigation of 19 insomnia cases and their matched controls (age,work) measured outdoor and indoor sound pressure levels during sleep (Kageyama et al. 1997). The study showed that road traffic noise in excess of 30 dB LAeq for nighttime induced sleep disturbance, consistent with the results of Öhrström (1993b)" Special attention should also be given to the following considerations:
While the WHO guidelines are not specifically for noise from wind farms, I find it interesting that the WHO suggests noise levels below 30dBA for low frequency components, while all I could find on the Department for Business Enterprise & Regulatory Reform where sound levels for general noise was an absolute level in the range 35-40dBA. Confused???? Me too! If we take into account that sound levels indoors are supposed to be 10dBA lower and that we have some 'environmental noise' from wind in the hedges, we should be all right. But then there is the individual perception of noise and the different sound quality.... RES and Novera Energy will be producing sound maps as part of the environmental impact assessment. I have further been told, that RES would meet the requirements of any planning conditions set by the local authority, which would usually relate to keeping within certain noise levels which they would design the wind farm to achieve. This may include the use of operational procedures to ensure that obligations are met. We should make sure, that noise levels are included in the planning conditions. And it should be well defined, which company is responsible for 'operational procedures' if the noise levels are exceeded.... Other Links:
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