The UK Government has now published its long anticipated update to ETSU-R-97, the guidance that has underpinned wind farm noise assessment for nearly 30 years.
While this is an important milestone, the key for developers is simple:
This is a minor evolution of the existing approach, not a fundamental change.
We have seen a lot of articles on social media which miss this point entirely. For projects currently in planning, under development, or considering repowering, the noise assessment methodology set out in ETSU-R-97 remains firmly intact. This should be seen as a relief for developers – the update provides helpful clarification rather than any additional constraint.
What Hasn’t Changed
The core principles of ETSU‑R‑97 are preserved, including:
- The use of background noise related limits;
- The continued role of lower limiting values (LLVs) (35-40 dB(A) daytime, 43 dB(A) night-time);
- The familiar +5 dB above background approach;
- The use of a 35 dB(A) fixed LLV where sufficient separation distance exists; and
- Higher limits (45 dB(A) LLV) for financially involved properties.
In short, the way wind farm noise is assessed remains consistent with established practice.
What’s New (and What It Means in Practice)
The 2026 update introduces a series of targeted refinements and clarifications, rather than wholesale change. The vast majority of the updates are to simply incorporate what has long been applied by experienced assessors (such as our team at Metrica) as a matter of course, rather than introducing anything new.
1) Alignment with national noise policy
- ETSU compliance is inherently designed to avoid significant adverse effects; and
- Some minor effects (above LOAEL) may still occur, but this does not mean that further mitigation is required.
2) Amplitude Modulation (AM) formally incorporated
The update adopts the Institute of Acoustics methodology for rating AM, allowing corrections of up to +5 dB.
However, it confirms that that AM should not (and cannot) be assessed at the planning stage. Instead, example planning conditions are provided to manage it if it arises.
3) Clearer approach to cumulative noise
The principle of cumulative assessment remains unchanged. However, the guidance now confirms that where predicted noise is very low (i.e., <25 dB(A)), or the proposed wind farm would not materially increase the existing cumulative wind turbine noise level, then cumulative assessment is not required for areas or receptors where either of these criteria apply.
This is the essentially the methodology already being applied as a matter of best practice, so the formal inclusion of this into ETSU-R-97 should be seen as a welcome clarification, not a constraint.
4) Introduction of the ‘headroom’ concept
A notable refinement is the distinction between. The Total Noise Assessment Criteria (TNAC), and Site-specific limits, which may be set slightly below the TNAC. This helps preserve capacity for future wind development in an area. Again, this is already the approach taken by experienced acousticians, so there is no change for any well-designed schemes.
5) Scope clarifications
The update confirms that certain matters can be scoped out on the basis of there being no reasonable prospect of a significant effect, including:
- Infrasound (<20 Hz);
- Low frequency sound; and
- Ground-borne vibration.
Small turbines (<50 kW) are also treated as having localised impacts only, and can therefore be scoped out with reasonable justification.
Areas Where Interpretation will Continue to Evolve
As with any update, there are aspects that will require professional judgement, including:
- The definition of financially involved properties; and
- How ETSU applies to non-standard residential receptors (e.g., caravans, campsites, etc).
Whilst additional clarity on these matters would have been welcome, these are planning / legal matters as much as they are technical noise matters, so the fact that the update is not more definitive in this regard it is not unexpected. The approach to these matters therefore has not changed.
What This Means for Developers
For developers, our message is clear :
- No fundamental change to how wind farm noise is assessed;
- Greater clarity and consistency, rather than new barriers; and
- Existing projects can proceed with confidence.
How Metrica can Help
Whilst the detail does matter, that’s where we come in. With over 16 years’ experience in wind farm noise assessment, our job is to understand the guidance inside out so you don’t have to. Please get in touch if you would like to discuss in person – we are here to help.
