THE USE OF PROXY MEASUREMENTS TO DETERMINE WIND FARM NOISE COMPLIANCE, WHAT ARE THE OPTIONS, IS THERE A NEED FOR FURTHER GUIDANCE?

THE USE OF PROXY MEASUREMENTS TO DETERMINE
WIND FARM NOISE COMPLIANCE, WHAT ARE THE
OPTIONS, IS THERE A NEED FOR FURTHER GUIDANCE?
J Mackay TNEI Services Limited, Newcastle Upon Tyne. UK
M Coulon TNEI Services Limited, Newcastle Upon Tyne, UK
J Baldwin TNEI Services Limited, Newcastle Upon Tyne. UK
1 INTRODUCTION
1.1 Background
As more wind farms are built in the UK the requirement for noise compliance monitoring is
increasing. Compliance monitoring is usually undertaken for one of three reasons:
1) the wind farm operator undertakes the assessment voluntarily as part post commissioning
works;
2) monitoring is required to satisfy a planning condition: or.
3) monitoring is required following receipt of a complaint relating to noise.
The method adopted for compliance monitoring can vary slightly depending on the site and the
purpose of the monitoring. useful general guidance is provided in the Institute of Acoustics
document 'A good Practice guide to the application of E TSU-R-97 for the assessment and rating of
wind turbine noise' (GPG) and particularly in the associated Supplementary Guidance Note 5 ☁Post
Completion Measurements: (SGN5).
Typically, compliance monitoring is undertaken at noise sensitive receptors, either at those located
closest to the site for voluntary or conditioned monitoring or at the complainant's properties in the
event of a complaint. For modern wind farms set back distances between the monitoring locations
and the turbines are typically 400♥1000m and the signal to noise ratio at these distances can be low
making it difcult to accurately identify the specic noise contribution from the wind turbines.
Increasingly wind farms are being planned and built in clusters. meaning that compliance monitoring
sometimes needs to consider cumulative noise impacts too. The GPG provides a number of
solutions which can be adopted to ensure appropriate noise limits are set for individual
developments (as discussed in Section 5 of that document). Many of the solutions suggested in the
GPG result in developments being set very low noise limits which are sometimes below the
background noise level.
Setting of limits which are below the background noise level is not a new practice in acoustics or
indeed for wind farm noise. ETSU-R-97. which was published in 1996. detailed that a xed 35dB
LAW limit might be appropriate from wind speeds up to 10mls for ☜single turbines or wind farms with
very large separation distances between the turbines and the nearest properties☝. Adoption of this
simplied limit often means that the limit is below the background noise level. particularly at higher
wind speeds.
The challenges associated with undertaking compliance measurements against the simplied 35dB
limit were recognised by Garnet and Sutherland when they presented a paper:1 at Acoustics 2015
on that very topic. additionally it is also referenced in SNGS. which notes in paragraph 2.4.8