Wind Farm Noise Impact Assessment BASELINE NOISE MEASUREMENTS

The use of baseline data in ETSU-R-97

On-site wind speed controlling SWL of turbine Wind speed controlling wind induced noise 5.6 Background noise level, L A90,10min 10 minute averaged wind speed

1. Establish requirement for baseline data 2. Identify extent of areas requiring baseline representation 3. Broad survey location planning 5. Installation / micro-siting 4. Consultation & detailed survey design 5. Analysis & reporting General baseline survey process

The noise survey Survey locations dB L A90 > – – – – – – – – 35

The noise survey Survey locations Consideration of other wind turbines The existing wind farm should not be considered as part of the prevailing background noise. ETSU-R-97. Review available environmental information Consider pre-determined background noise levels Select survey locations away from existing turbines Other distant proxy locations Shut-down existing turbines Post-survey data processing Ensure noise from existing turbines does not influence survey data for a proposed wind turbine development.

The noise survey Survey locations Timing Equipment Synchronisation of data Duration Background noise surveys may be carried out at any time of the year provided that seasonal effects leading to raised noise levels can be excluded by selection of measurement position or by exclusion of non-typical data during analysis. Type 1 sound level meter Appropriate wind shield SLM calibrated within 2 years Field calibrator calibrated within 1 year WindNoise Rain excluded data Other excluded data Valid data points Background noise trend Turbine immission level ETSU-R-97 IoA GPG 200 valid data points5 valid data points per 1 m/s wind speed bin

Survey locations: micro-siting When setting up a logger, observe sources of constant noise, such as: Practical constraints will always influence ideal survey choice Streams Water features Boiler outlets Occupier driven requests Are local noise sources typical ? Shielding from distant sources Note foliage types Effects on different aspects of property relative to wind farm Extent that wind disturbed vegetation may vary around property Industrial Farm machinery Roads Consider:

Wind reference – options Conventional 10m mast SODAR/Lidar multiple heights Taller height meteorological mast

Analysing the survey data

The challenge to using baseline data Inherent variability presents several questions: Conditions - what are ‘typical’ and ‘representative’ conditions ? Locations - how many locations are required to represent all areas ? Duration - what survey duration is needed to capture ‘typical’ conditions ? Variations - what are ‘typical’ and ‘atypical’ variations ? Representation - from the range of valid levels measured, how can the data best be represented for making and supporting decisions Understanding characteristics & sources of variability is critical to survey design & analysis