Wind turbines do make noise, but it is worth putting this in context. The indicative maximum noise level of a wind farm at 350m (1150ft) is usually roughly comparable to the sound of leaves rustling in a general breeze (in the region of 35-45 dB). With this level of noise, two people can be up to at least three metres (or about 10 feet) apart and still hold a conversation without disruption.
We take seriously the potential for noise impacts from all forms of new development on local communities and those working in the vicinity. Noise impacts are considered within the planning process before a decision is taken on whether or not to grant consent to an onshore wind project. Existing planning guidance states the ETSU-R-97 approach should be used to assess and rate noise from wind energy developments. The likely impact of noise from wind turbines on local residents and those working in the vicinity is always considered in relation to the existing background noise levels.
Hayes Mckenzie report on wind turbine noise
The Government is keen to ensure planning authorities and developers are clear on best practice, to provide greater certainty and consistency within the planning system. Following concerns raised with government about the consistency of approaches taken to the practical application of ETSU-R-97, the Government commissioned consultants Hayes Mckenzie to carry out a research project to analyse matters arising in the consideration of noise impacts when determining wind farm planning applications in England. The report has now been published:
The review has highlighted the potential problems faced by local planning authorities dealing with noise assessments for wind farm sites, both in terms of the way the documents are structured, and in the variations in the way some factors are taken into account in the assessments. This suggests best practice guidance is required to confirm and, where necessary, clarify and add to the way ETSU-R-97 should be implemented in practice.
Variation in approach in a number of different areas was found including:
- Background noise measurements, and interpretation of data
- Prediction methodology used
- The way ‘wind shear’ is taken into account
In addition, it is considered that guidance could usefully be provided on:
- Setting the day-time hours noise limit within the range specified by ETSU-R-97
- Dealing with the issue of modulation in the noise
- What constitutes a ‘financially involved property’
Consideration could be given to:
- A simplified assessment procedure of limiting turbine noise to a fixed level
- The structure of planning conditions especially where cumulative impact of more than one site occurs
Any additional guidance should also review, or at least acknowledge, the changes which have been made to some of the documents referred to in ETSU-R-97; such as the replacement of IEC651 with BS EN 61672, the update of BS4142 from the 1990 version to the 1997 version, and the latest World Health Organisation (WHO) guidance on noise limits to prevent sleep disturbance.
The Institute of Acoustics is taking forward work to develop good practice guidance and expect to issue a draft for consultation in early summer 2012. More information on this work is available on a press notice on the Institute Of Acoustics website.
The Hayes McKenzie report was concerned with analysing whether noise assessments were carried out consistently rather than with making and assessment of ETSU-R-97 itself. The Government continues to support ETSU-R-97. Current methods used in practice to implement the ETSU-R-97 guidance continue to apply until supplementary best practice guidance is published.