Draft National Wind Farm Development Guidelines - July 2010

As noted in Section 6.3.1 of AS4959–2010, background noise levels should be monitored as
LA90 levels concurrent with wind speed and direction. Monitoring should at least capture all
of the significant wind directions and speed ranges which appear in representative wind
statistics of wind at the site.
AS4959–2010 recommends that a minimum of 2000 monitored data points should be
available for analysis at each measurement location, covering “the range of wind speeds
and wind directions generally to be expected at the wind farm site and in particular the
range of wind speeds (at hub height) between the ‘cut-in’ and ‘rated’ wind speeds of a
WTG of the general type proposed for the site.”
It is suggested that the range of wind speeds included in monitored data be extended in
order to accurately capture the trend between background noise level and wind speed
at wind speeds up to rated power. Specifically, it is recommended that monitored wind
speeds extend 2m/s beyond the wind speed of rated power. In addition, it is suggested
that, where possible, at least 30 daytime and night-time data points should be collected
for each monitored integer wind speed bin.
In some cases it may be difficult and overly time-consuming to obtain measured data
covering the desired range of wind speeds, wind directions and periods of the day. In such
cases it may be suitable to monitor for a lesser, fixed amount of time so long as
appropriate reasons for the shorter monitoring period are provided.
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guidance on positioning of wind speed/direction monitoring equipment.
All noise and wind monitoring equipment should satisfy the requirements of AS4959–2010,
including the requirement for suitable protection of the microphone against windgenerated
noise through the use of an appropriate wind sock. The relevant authority may
have additional specific requirements regarding the control of wind generated noise over
the microphone and should be consulted. All wind speeds and direction should be
monitored at hub height or corrected to hub height reference according to Section 6.3.3
of AS4959–2010.
Confirm noise criteria using background noise monitoring data
Noise level limits should be established for all relevant receivers based on the background
noise monitoring data collected. Ideally the noise level limits should be specified at
nominal wind speed intervals of 1m/s between the wind speed at which the WTG starts to
generate electricity (‘cut-in’ wind speed) and the wind speed at which the WTG reaches
its maximum power generation (‘rated’ wind speed).
Representative background noise level curves may be established for each relevant
receiver using the regression analysis techniques described in Section 6.3.4 of AS4959-2010.
Noise level Limits should then be established using these background noise level curves.
Section 6.3.1 of AS4959-2010 notes: Where regression curve analysis does not conform to
the expected trends, i.e. there is not a clear relationship between increasing wind speed
and increasing background noise levels or there appears to be more than one distribution,
then further investigations are necessary to determine possible causes and section 6.3.4 of
the standard notes: Consideration should be given to carrying out separate correlations of
background sound levels with wind speed for different wind directions and/or times of day,
particularly where atmospheric stability issues are apparent or are suspected.
Should background noise levels vary with wind direction in a way that is not in accordance
with expected trends then the cause of the variation should be examined. Data may
need to be separated and separate limits determined based on wind direction, time of
day or atmospheric stability considerations.
If such variations are observed, background noise data should be analysed for significant
variations in noise level with the factors identified as causing the different distribution.
Draft National Wind Farm Development Guidelines – 2 July 2010 Page 51