Sunday, December 13, 2009

"This sentence is dangerous"

The Den Brook Judicial Review Group were recently successful in a Freedom of Information request to obtain drafts of a government-contracted report about noise levels from wind turbine facilities: "The measurement of low frequency noise at three UK wind farms" by Hayes McKenzie Partnership Ltd. for the (former) Department of Trade and Industry, 2006, contract no. W/45/00656/00/00; URN no. 06/1412. See the material posted at National Wind Watch, by courtesy of the Den Brook Judicial Review Group.

3rd draft, page 35:
It is important to note, however, that for Site 1: Location 1, the occupant complained of wind turbine noise only after being woken by the passage of a motor vehicle on the nearby A-Class road. As such, this indicates that, rather than wind turbine noise resulting in noise which is of sufficient level as to awaken a sleeping person, it is the inability to return to sleep associated with some audible wind turbine noise within the bedroom which is of more concern to that occupant. A difficulty in returning to sleep will result in tiredness the next day and all the associated descriptions of ill health which might be associated with a lack of sleep – this sentence is dangerous and could be read that windfarms cause ill-health which is not the intention. We need the report to stick to the facts that LFN is bleow the guidelines but that once woken by a car there may be problems getting gback to sleep for those with sensitive hearing as result of the windfarm – something like that.[Personal Details/Name of official removed under Reg 12(3) of the EIRs]
In the final report, page 48, the "dangerous" sentence has been deleted.

It is also interesting to note how the conclusion statements regarding aerodynamic modulation changed from draft to final report:

3rd draft, pages 45-46 (essentially the same from 2nd draft, not yet written in 1st draft):
The common cause of complaints associated with wind turbine noise at all three wind farms is the audible modulation of the aerodynamic noise, especially at night. Although the internal noise levels associated with this noise source are not high enough to result in the awakening of a resident, once awoken the audibility of this noise results in difficulties in returning to sleep.

The analysis of the external and internal noise levels indicates that it may be appropriate to re-visit the issue of the absolute night-time noise criterion specified within ETSU-R-97. To provide protection to wind farm neighbours, it would seem appropriate to reduce the absolute noise criterion for periods when background noise levels are low. In the absence of high levels of modulation, then a level of 38 dB LA90 (40 dB LAeq) will reduce levels to an internal noise level which lies around or below 30 dB LAeq with windows open for ventilation. In the presence of high levels of aerodynamic modulation of the incident noise, then a correction for the presence of the noise should be considered.
Final report, page 67 (deletions indicated, and additions in italics):
The common cause of complaints associated with wind turbine noise at all three wind farms is not associated with low frequency noise, but is the audible modulation of the aerodynamic noise, especially at night. Although the internal noise levels associated with this noise source are not high enough to result in the awakening of a resident, once awoken the audibility of this noise can results in difficulties in returning to sleep. It is also not uncommon for a wind farm to be identified as a cause of the awakening although noise levels and the measurements/recordings indicate to the contrary.

The analysis of the external and internal noise levels indicates that it may be appropriate to re-visit the issue of the absolute night-time noise criterion specified within ETSU-R-97. To provide protection to wind farm neighbours, it would seem appropriate to reduce the absolute noise criterion for periods when background noise levels are low<. In the absence of high levels of modulation, then a level of 38 dB LA90 (40 dB LAeq) will reduce levels to an internal noise level which lies around or below 30 dB LAeq with windows open for ventilation aerodynamic modulation and the means by which it should be assessed. In the presence of high levels of aerodynamic modulation of the incident noise, then a correction for the presence of the noise acoustic feature should be considered.
wind power, wind energy, wind turbines, wind farms, environment, environmentalism, human rights, animal rights