Review of noise guidance for onshore wind turbines: report for UK government 

This study aimed to answer the question: in view of government policies on noise and commitments to Net Zero, should the existing ETSU-R-97 noise assessment guidance for wind turbines be updated, and if so, how?

Onshore wind is recognised as one of the lowest-cost sources of renewable electricity generation. A sustained growth in capacity is also seen as a keen enabler of the UK government’s commitment to deliver a net zero economy by 2050.

Using our expertise in acoustics, planning and environmental assessments for renewables, we delivered this study on behalf of the UK government Department for Business, Energy & Industrial Strategy (BEIS) to review the UK onshore commercial wind turbine noise assessment guidance (a document known as ETSU-R-97).

Since the ETSU-R-97 guidance was published in 1996, the context has changed:

• The need for onshore wind energy is more urgent
• Technology has advanced
• New research has been undertaken
• Understanding of wind turbine sound has progressed, highlighting in particular the potential impact of amplitude modulation (AM, described below)

Our report recommends key areas of the guidance that would benefit from being updated, and provides recommendations for further evidence needed to support updates identified. These include revisiting the framework of noise limits, and establishing new guidance to support assessment and control of the potential impact of AM.

Our recommendations will help to ensure that guidance for local planning authorities, developers and operators is the most relevant and up-to-date possible, supporting robust planning and assessment processes for managing the potential impacts of noise from wind turbines, which in turn will contribute to sustainable delivery of onshore wind energy.

How did we approach the study?

WSP’s acoustics team worked closely with a steering group including BEIS, the Department for Environment, Food & Rural Affairs (Defra), the Department for Levelling Up, Housing & Communities, the Scottish Government, the Welsh Government, and the Northern Ireland Executive.

The study comprised three workstreams:

• Evidence review
• Stakeholder engagement
• Field measurements

The evidence review employed two stages of systematic literature search and screening of a wide range of publications identified from peer-reviewed literature databases, scientific conferences, official reports, guidelines and standards. In total, 132 publications were reviewed for evidence relevant to the research.

The stakeholder engagement survey included a questionnaire, and focus interviews with identified key stakeholders. In total 32 organisations responded to the questionnaire and 6 key stakeholders were interviewed.

The field measurement exercise collected a ‘snapshot’ of wind turbine sound data from seven wind farm sites during conditions thought likely to enable the detection of amplitude modulation at ranges representative of wind farm neighbours.

What is amplitude modulation?

A feature of wind turbine sound commonly known as amplitude modulation (AM). This is a regular fluctuation of the sound level associated with the passage of the blades. It is often described subjectively as a ‘swish’ or ‘whoomph’ sound.

Areas for increased focus:

Our analysis indicates that the existing guidance would benefit from updating in two key areas:

1. Noise limits: The ‘noise limits’ defined in the ETSU-R-97 guidance are based on information that reflected the state of knowledge and turbine technology at the time. The research indicates that these should be revisited in view of advancements in onshore wind turbine technology, knowledge and scientific evidence of the potential impact of wind turbine noise, and the evolution of government noise policies in each of the devolved administrations of the UK. These developments could be reflected in a new framework for assessment and control of noise impact, in terms of addressing health outcomes and expected behavioural responses associated with wind turbine noise.
2. Amplitude modulation guidance: The research also indicates that the current ETSU-R-97 guidance does not fully address the potential impact of AM in wind turbine sound. The evidence identified in the study, including indicative information from the field measurements, suggests that the assumptions about AM adopted in ETSU-R-97 do not fully represent the nature of AM as experienced and measured. Existing evidence could be used to help develop suitable guidance on controlling AM, and stakeholder views suggest this would be welcomed.

Our report also includes recommendations on further areas of the guidance likely to benefit from updating to reflect the latest evidence addressing methods of measurement, prediction, data analysis, assessment and control for wind turbine sound and noise.

Recommendations for future studies:

Our report for BEIS identifies further key evidence needed to support some of the recommended updates, and to inform planning and consenting around onshore wind farms in the UK, including:

• A systematic review and meta-analysis of evidence on the effects of wind turbine sound exposure on noise annoyance and sleep quality,
• A more detailed review of national and regional guidelines applied in overseas territories to manage wind turbine noise,
• A study to consider the effectiveness of the current ‘relative impact’ approach to controlling wind turbine noise based on existing background sound environments,
• A study to consider the effectiveness of the ‘relative impact’ approach to controlling wind turbine noise and identification of effect thresholds.

Attaining suitably robust evidence to support guidance updates is likely to require government, industry, academia and other stakeholder groups to work together to achieve mutual interests in providing local planning authorities, environmental protection departments, developers and operators with the most relevant and up-to-date guidance possible for planning and assessing noise from wind turbines. Achieving this aim will ensure the effective management of the potential impacts of wind farm noise, while supporting government objectives for achieving Net Zero.

The findings of the study must be considered within the context of its strengths and limitations, which are detailed and discussed in the report. The authors would like to stress that this review represents only an initial step in any process of updating the existing guidance that may be decided on in the future; the report itself does not provide new guidance or supersede any parts of the current policy or guidance frameworks in place in any of the devolved administrations.

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