By Diarmuid Keaney MSc. in Applied Acoustics, MIOAICAN AcousticsContact: diarmuid@acoustics.iewww.acoustics.ie

Wind Turbine NoiseETSU-R-97

and

emerging guidance on

Wind Farm Developments

Rev:6

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.

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”

Topics:

Overview of today’s talk....

EN 61400-11

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.

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)

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.

Source: ‘Wind Turbine Noise’ Warner,Bareiß & Guidati

Generate noise from 20Hz to 3600hz

Varies with:-wind speed-blade pitch-blade speed

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 UnitWorking 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

How a baseline noise survey is conducted

Source: IoA Good Practice Guidelines Draft

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

The Baseline Study combined with Met Mast info

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

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

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

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.

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.

• 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

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

Emerging Guidance (Ireland)Wind Energy Guidelines: Review of noise and shadow flicker standardsSubmission 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.

The IoA Good Practice Guidelines will most

certainly address this issue.

Source: IoA Good Practice Guidelines Draft

Other guidance and papersNumber 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)

Thank you for your time.

Contact Details

Diarmuid KeaneyLinkedIn (search): Diarmuid KeaneyICAN Acoustics

E-mail: diarmuid@acoustics.ieWeb: www.acoustics.ie

Tel: 01-4403869 and 091-588555Low Call National: 076-6021356N.I. 0161-660-1611