Wind turbine noise
Wind turbine noise has long been a contentious issue in the acoustics world. But with the rise of micro generation and the ability for landowners to effectively host a turbine “for free” and save money on power, more and more small turbines are appearing across our landscape.
Although the technical debates will continue, not least regarding whether the noise limits set in the standard are appropriate, at the current time the standard for addressing turbine noise is ETSU-R-97. If you need a noise assessment for planning, this will typically be the benchmark against which measurements must be taken and assessments carried out.
It is worth noting, however, that some Local Authorities have their own variations on methodologies and limits, or permitted development orders relating to wind turbines. It’s always important to contact your local planning authority first, to see what their requirements are.
ETSU-R-97 “The assessment of noise from wind farms” was published in September 1996 by the Department of Trade and Industry. 18 years ago, the wind turbine demographic was very different and the concern was with large wind farm developments above 50 kW– micro generation was not on anyone’s mind.
As such the procedure is considered complex for smaller developments such as single turbines.
Institute of Acoustics Good Practice Guide on Wind Turbine Noise
In May 2013 the Institute of Acoustics released “A good practice guide to the application of ETSU-R-97 for the assessment and rating of wind turbine noise”.
This clarifies the position for consultants with regard to measurement locations and procedures and in particular clarifies the complex data analysis requirements, in which all noise data must be correlated with weather readings.
What It Means for the Customer
The technical aspects of wind turbine noise assessment are, of course, a job for the acoustic consultant. But if you are thinking of installing a turbine, you will want to know a little about what the noise assessment entails.
Don’t immediately assume that a full noise survey and assessment will be required; your acoustic consultant can help engage with the local planning authority to determine if this is the case. The minimum ‘study area’ for an assessment is the area within which noise from the proposed wind turbines may exceed 35 dB LA90 at up to 10 m/s wind speed. Therefore turbines which are remote from other properties may need only a desktop scoping assessment in order to demonstrate that they will not affect residents.
If you do need a survey, this is likely to be extensive – at least two weeks of measurement, possibly at more than one location. The noise consultant will also need to install a weather mast in order to correlate meteorological conditions with the noise measurements. The survey period can be extended if the weather conditions do not comply with requirements.
As such, it’s important to have an acoustic consultant on board early in the process; calling two weeks before the planning committee sits is likely to lead to disappointment!
Can dBx Acoustics help you?
As ever, dBx Acoustics is equipped to carry out both desktop assessments and long-term noise surveys to help with planning for proposed wind turbines. If you have any questions or would like a quote, please do contact us!