1. By Diarmuid Keaney MSc. in Applied Acoustics, MIOA
ICAN Acoustics
Contact: diarmuid@acoustics.ie
www.acoustics.ie
Wind Turbine Noise
ETSU-R-97
and
emerging guidance on
Wind Farm Developments
Rev:6

2. Brief Introduction
 Diarmuid Keaney
 Company: ICAN Acoustics www.acoustics.ie
 M.Sc. in Applied Acoustics (University of Derby)
 Diploma in Acoustics and Noise Control (University of Ulster)
 B.E. from NUI.

3.  A brief review of ETSU-R-97
 Emerging guidance
“A GOOD PRACTICE GUIDE TO THE APPLICATION OF
ETSU-R-97 FOR WIND TURBINE NOISE
ASSESSMENT”
Overview of today’s talk....

4. EN 61400-11

5. Typical Wind Turbine Sound Power Levels
Sound power levels from a wind turbine typically vary with the speed of a
wind turbine (higher wind=greater sound power level, lower wind=lower sound power levels)
•At 4m/sec (ref height of 10m) the sound power level could be 95dB(A)
•At 9m/sec (ref height of10m) the sound power level could be 104dB(A)
Note: Wind speeds can vary across a site, hence wind turbines can emit
different noise levels across the same site.

6. A wind turbines Sound Power Level is frequently reported at a 10m reference
height (good data)
Hub
Height
Hub
Height
Hub
Height
Hub
Height
Hub
Height
Wind speed (ref 10m high) 80m 90m 100m 110m 130m
5m/sec 96dB(A) 97dB(A) 99dB(A) 102dB(A) 104dB(A)
6m/sec 99dB(A) 99dB(A) 100dB(A) 99dB(A) 99dB(A)
7m/sec 102dB(A) 102dB(A) 102dB(A) 102dB(A) 102dB(A)
8m/sec 104dB(A) 104dB(A) 104dB(A) 104dB(A) 104dB(A)
9m/sec 104dB(A) 104dB(A) 104dB(A) 104dB(A) 104dB(A)
10m/sec 107dB(A) 107dB(A) 107dB(A) 107dB(A) 107dB(A)

7. So how do wind turbines make noise?
What makes noise?
For modern wind turbines this is
mainly aerodynamic noise.
Older turbines generally had more
mechanical noise
Note: It is a common misconception
that modern turbines do not generate
tonal noise, however this is not the
case. Measurement data frequently
shows elevated tonal elements at
certain speeds or modes of operation.

8. Source: „Wind Turbine Noise‟ Warner,Bareiß & Guidati
Generate noise
from 20Hz to
3600hz
Varies with:
-wind speed
-blade pitch
-blade speed

9. ETSU-R-97 : Prepared by a working group in September 1996
for the Department of Trade and Industry in the UK (now 17
years old)
ETSU – Energy Technology Support Unit
Working Group: Acoustic Consultants ,County Councils, District
Councils, Solicitors, Power Companies.
BTW: The DoEHLG Guidelines issue in 2006, some 10 years
after ETSU-R-97.
ETSU-R-97

10. How a baseline noise survey is conducted
Source: IoA Good Practice Guidelines Draft

11. Met Mast measures at
two heights to determine
the wind speed at a
reference height of 10m
At a noise sensitive receptor Wind speed on the site

12. The Baseline Study combined with Met Mast info

13. BACK to our Baseline Study data.......

14. LA90 =35~40dB (Daytime) or 5dB(A) above background

15. LA90 =43dB (Night) or 5dB(A) above background

16. What an ETSU-R-97 assessment should include as a minimum
A noise impact assessment for a wind farm should include:
1. A baseline noise study to examine the existing noise climate at ALL
operational speeds for the proposed wind turbines (5m/sec, 6m/sec,
7m/sec .)
2. The selection of a suitable wind turbine using quality noise data that
is guaranteed by the manufacturer (via an independent test house).
3. The manufacturer should issue a guaranteed sound power level.
4. The building of a 3-D noise contour model using GIS data and the
turbine data modelled at the planned heights.
5. A noise assessment of the noise impact created at all noise sensitive
locations within the immediate vicinity.

17. Our own findings in relation to critically reviewed wind farm
proposals and the application of the data in Ireland.
• Noise impact assessments where the promoter or EIS author has not even
conducted a baseline study.
•The use of turbine noise data which clearly states in the small print that it should
not be used for prediction purposes and that it does not form any part of a
guarantee.
•Opening paragraphs where the author of the EIS claims the use of best practice
guidance such as ETSU-R-97 and yet the author uses the less onerous DoEHLG
limiting values of 45dB which suits his/her assessment (usually in favour of the
applicant)
•Attempted assessments where the assessment method is not understood by the
author and in some cases the person who has conducted the assessment has
formal qualification in acoustics.

18. •Octave band data is not used in the prediction process, so absorption
effects due to air is not considered.
•Poor modelling using generic wind farm packages where there is a bolt-on
„Noise Module‟. Most of these modules are over simplified and can be in
highly accurate and limited.
• Predictions that are conducted at a single wind speed using a concept
called “Critical Wind Speed” which is not in accordance with ETSU
guidance.
•Higher noise levels at houses justified on the ground that those in the
dwellings have a financial interest in the wind farm. ETSU states a higher
limiting value of 45dB is appropriate for these houses.
More of our own findings

19. Emerging Guidance (UK)
"Good Practice Guidance to the application of ETSU-R-
97 for wind turbine noise assessment".
On 18/12/2012: The Institute of Acoustics has published the responses to its
consultation on "Good Practice Guidance to the application of ETSU-R-97
for wind turbine noise assessment".
 On 21/05/2013 (NEXT TUESDAY): The IoA will launch the “A GOOD
PRACTICE GUIDE TO THE APPLICATION OF ETSU-R-97 FOR WIND TURBINE NOISE
ASSESSMENT”
 NOTE: This is an addition to the 17 year old ETSU-R-97 Document

20. Emerging Guidance (Ireland)
Wind Energy Guidelines: Review of noise and shadow flicker
standards
Submission deadline: 15th Feb 2013
• Our company made a submission (early Feb 2013) as did the Irish
Branch of the Institute of Acoustics.
•We understand that there were 550 submissions.
• We await formal and official confirmation of receipt of our submission
as of the 17th of May 2013.
•SEAI recently issued a tender request to desk study of peer reviewed
studies and guidance un other countries.

21. The IoA Good Practice Guidelines will most
certainly address this issue.
Source: IoA Good Practice Guidelines Draft

22. Other guidance and papers
Number of papers in circulation about specific topics such as the effects
of Low Frequency Noise (LFN), Infra Sound or Amplitude Modulation
(AM):
To assist with study credibility always check:
 The qualifications of the author and ascertain if they are suitably qualified in this specific
area?
 Who are the authors and what was each authors contribution to the study?
 Has the author(s) any potential bias (is this truly an independent study?)
 Who the paper has been commissioned by and why (this should be disclosed)?
 Establish if the paper has been ‘peer-reviewed’ by qualified peers.
 If the paper has been published by any Journal and if not, why not? ( for example Journal
of Applied Acoustics).
 Is the paper is conclusive in its findings ? (watch out for more research needed)

23. Thank you for your time.
Contact Details
Diarmuid Keaney
LinkedIn (search): Diarmuid Keaney
ICAN Acoustics
E-mail: diarmuid@acoustics.ie
Web: www.acoustics.ie
Tel: 01-4403869 and 091-588555
Low Call National: 076-6021356
N.I. 0161-660-1611