- National Wind Watch: Wind Energy Documents - https://www.wind-watch.org/documents -

Den Brook Amplitude Modulation Condition

Den Brook Timeline:

2005  –  RES submit planning application to West Devon Borough Council (WDBC) for nine wind turbines in the Den Brook valley between Bow, Spreyton and North Tawton
2006 Jan  –  WDBC refuses planning permission
2006 May  –  RES file Planning Appeal
2007 Feb  –  Planning Inspector grants planning permission
2007 Mar  –  Mike Hulme lodges Judicial Appeal
2008 Mar  –  Judicial Appeal refused by High Court
2008 Apr  –  Hulme appeals to Court of Appeal
2008 Aug  –  Court of Appeal requires redetermination of Planning Appeal by Inspector
2009 Dec  –  Inspector grants planning permission with conditions [1]
2010 Jan  –  Hulme lodges appeal to Court of Appeal
2011 May  –  Court of Appeal upholds planning permission and conditions [2]
2013 Apr  –  RES applies to amend AM conditions (see 2012 RES presentation on AM, tonality and impulses [3])
2013 Aug  –  RES withdraws application to amend AM conditions
2014 Feb  –  RES submits scheme for complying with AM conditions [4]
2015 Aug  –  RES begins construction

The “Den Brook Amplitude Modulation Condition”:

Excess amplitude modulation was defined in condition 20 of the December 2009 planning permission as any change, upon complaint, outside the dwelling, in LAeq,125ms of >3 dB in any 2-second period ≥5 times in any minute with LAeq,1min ≥28 dB and such excess occurring in ≥6 minutes in any hour.

“LAeq,125ms” is the equivalent A-weighted continuous sound level (average) over a 125-millisecond period, “LAeq,1min” over a 1-minute period.

In other words, a 125-ms pulse of 3 dBA or greater (3 dB being the difference in noise level detectable by the human ear) can not occur in any 2-second period five or more times in six or more minutes of any hour, when those minute-long average noise levels are 28 dBA or more.