January 12, 2007

Turbine noise driving Brit mad

"Wiggyjane" has described her distress over the noise of the 8-turbine (16-MW) Deeping St Nicholas wind energy facility on the U.K. site "Yes2Wind." Hers is not a so-called "aesthetic" complaint, as she was and still is supportive of wind energy and finds the turbines a fine addition to the landscape.

In response to a question about how far turbines should be from a residence, she writes:
Visually no problem -- they are quite beautiful at times to watch, menacing at others (with dark clouds behind and a storm approaching) but in the main soothing and rhythmic.

Noise -- well that's a different story altogether and will depend on the grid layout, the ground/soil type, your dwelling's position with regard to the predominant wind, the topography, geography and geology ... plus wind shear effects, particularly where there are stable air conditions ...

But we are 903 m (2,963 ft) away from the end of a row of five -- and that isn't far enough -- and we can go another 500 m (1,640 ft) and still have the same issues ... so at least a mile based purely on our experience. [Emphasis added.]
In another discussion, about Deeping St Nicholas, she writes:
I too live in Deeping St Nicholas -- but at the other end ... the northern end of the wind farm, and sadly we do suffer from both aerodynamic modulation and vibration from the low frequency noise. Environmental Health officials have already taken recordings that demonstrate a 20 dB differential between no wind turbine noise and turbine noise when they are running. [20 dB difference is experienced as a quadrupling of the noise level. --ED.]

There is no doubt anymore that some areas in some places near some windfarms DO cause problems. Not enough is really known about why this is the case, but we suspect that it's a combination of geography, topography, air conditions and ground density combined with the actual planting pattern of the turbines. In our case when all five nacelles are pointing at us normal life is impossible as they pick up resonance from each other and create an harmonic that resonates around and within the house, with levels that exceed ETSU [Energy Technology Support Unit of the U.K. Department of Trade and Industry] recommendations. ...

We have always supported the concept -- and indeed the visual look of wind turbines -- and never expected to have our lives totally disrupted and to be advised that it is not worth us building our new extension as our house would currently be unmarketable. ...

To the correspondent that started the thread -- at the southern end of the farm -- in Deeping St Nicholas itself you should have no problem ... and think of us when you sit in your garden enjoying the peace and quiet and go to bed to sleep at night, and stay asleep uninterrupted.
And more on sleep deprivation:
The hum/drone/whine is constant whether the turbines are running or not. [Emphasis added.] 24/7 it does vary a bit in intensity and volume but never goes away. Flicker isn't a real problem. The whoosh and thump noises are only really bad when the wind is in a specific direction (from SSE to SSW) then they top 40 dB(A), which when our ambient noise level is 20-25 dB(A) (pin drop quiet) means that they are very noticeable.

The wind direction also means that when we get all 5 nacelles "firing" at us, we get a harmonic and a quarter octave (???) in the farmyard that can exceed 60 dB(A).
One problem with noise regulations is that they use averages, and any limit is in fact only one that cannot be exceeded typically more than 10% of the time. So even where night-time limits are lower, which is usual, sleep can be still be legally disrupted. As Wiggyjane writes:
The problem is that raw noise measurements do not necessarily equate to ETSU regulations as they are not measured in LQ10's and LQ90's ... but what I can tell you is that our mean ambient is 22-25 dB(A) and last night ... we hit over 60 Db(A) but that was at the peak and would not be valid for ETSU. It made sleep well nigh impossible though -- and was the worst we have had for some months.
See "Wind Turbine Acoustic Noise," by Anthony Rogers et al., for a primer on sound measurement and regulation.

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