Draft National Wind Farm Development Guidelines - July 2010

assessment of wind farm noise emission can still be carried out satisfactorily without the use
of this type of equipment.
Where results of attended monitoring are unclear, particularly if they indicate noncompliance
with noise level limits, derived point measurement including sound power level
testing should be discussed with the relevant authority.
Undertake derived point measurements, including sound power level testing (as
required)
In extreme circumstances, where it has not been possible to demonstrate compliance with
noise level limits through both unattended and attended measurements and the relevant
authority agrees that compliance is likely to be achieved, sound power level testing of
selected wind turbines may be necessary to establish whether data used in noise emission
predictions is consistent with the on-site noise emission of the installed turbines.
Testing should be carried out according to the most recent version of IEC 61400-11. Where
practicable, the tested wind turbines should be those closest to the Receiver where noncompliance
has been demonstrated. The testing requirements of IEC61400-11 are
restrictive and testing of some turbines may not be possible.
In addition, derived point measurements should be carried out at a suitable location
between the wind farm and the receiver location which is the subject of the assessment.
Wind farm noise emission should dominate the background noise level at the selected
location. Attended measurements should be carried out and analysed according to
Undertake attended monitoring (as required) above.
Measured levels of wind farm noise emission should then be compared with predicted
levels at the derived point location. The correction factor should be the difference
between the measured and predicted levels, determined at each wind speed. The
correction factor should be applied to predicted wind farm noise emission levels at the
original receiver location to arrive at derived wind farm noise emission levels. These derived
levels may be compared with noise level limits at each integer wind speed to determine
compliance.
Close liaison with the relevant authority is expected for this process.
Address incoming complaints (as required)
Complaints should be handled as per the procedures developed during the Construction
noise phase (Prepare complaints handling procedures, page 56).
Assess noise characteristics (as required)
As indicated in A.2.1 above, the characteristics of tonality, excessive amplitude
modulation and impulsiveness are not normally expected to occur as part of the noise
emission from a correctly-functioning wind farm.
Nevertheless, an objective assessment may be required as part of post-construction noise
monitoring or complaint-handling procedures.
These Guidelines offer suggested methods of assessing each of the above characteristics,
as detailed in Table B-4 below. Concurrently, the relevant authority should be consulted to
identify any specific requirements they may have for assessment of noise characteristics.
Draft National Wind Farm Development Guidelines – 2 July 2010 Page 59