11/00713/F - Borough Council of King's Lynn & West Norfolk

ETSU-R-97 states that separate noise limits should apply for day and night time as during
the night time the protection of external amenity becomes less important and the emphasis
should be on preventing sleep disturbance. In areas of very low background, the introduction
of a new noise source can cause disturbance and dis-amenity at levels lower than 43 dB (A).
The night time background noise measurements within the Environmental Statement include
measurements as low as 16.3 and 17.6 dB(A) at wind speed of 4 m/s and 25.6 and 27.9 dB
(A) at a wind speed of 7 m/s. A limit of 43 dB (A) at this location allows for noise to increase
by as much as 26.3dB (A) during wind speeds of 4 m/s. A 10 dB increase is perceived as a
doubling of noise and a 20 dB increase is perceived as quadrupling of the noise. This is
considered to be unacceptable. PPS 22 acknowledges that the difference between the noise
of the wind farm and the background noise is liable to be greatest at low wind speeds.
Excessive Amplitude Modulation (EAM) caused by wind shear, normally arises in stable
weather conditions where the wind speeds are low at ground level and therefore background
noise is low. The higher wind speeds at hub height cause the turbines to produce more
noise which will be more noticeable at ground level due to the pre existing low background.
Where this problem has occurred at residential properties it has resulted significant levels of
disturbance and disruption to sleeping patterns.
Community Safety and Neighbourhood Nuisance (CSNN) have recommended 5 conditions
in relation to noise issues in order to ensure material harm will not result to residential
occupiers. In addition it is stated for the prevention of dis-amenity or disturbance due to
noise at residential dwelling, this criteria will not be relied upon in the determination of
Statutory Nuisance and that if authorised officers of the Borough Council of Kings Lynn and
West Norfolk are of the opinion that a Statutory Nuisance is being caused by the Wind Farm,
that they will fulfil their obligations under the Environmental Protection Act 1990.
Shadow Flicker
Under certain circumstances of geographical position and time of day, the sun may pass
behind the rotors of a wind turbine and cast a shadow over nearby properties. When the
blades rotate shadow flicks on and off. The effect is known as shadow flicker.
The ES analysis concludes that there is only one house within 930m of any turbine (known
as ‘The Cottage’). However, no instances of shadow flicker have been predicted to occur to
this property.
Reflected Light
Turbines can cause flashes of reflected light, which can be visible over long distances. It is
possible to ameliorate the flashing but it is not possible to eliminate it completely. Careful
choice of blade material and colour can significantly reduce this effect. The applicant
proposes to use a semi-matt surface finish to reduce the light reflection. It is suggested that
details of material and colour can be conditioned to ensure appropriate materials are used.
Ice Shedding
During periods of extreme cold weather, a build up of ice on turbine blades can occur. If ice
does build up on the blades there can be instances of ice shedding when the turbine is
started up. Most wind turbines are fitted with vibration sensors, which can detect any
imbalance which might be caused by the icing of blades and prevent the turbine from
operating. Ice shedding can therefore be avoided.
10/01419/FM Development Control Board
25 July 2011
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