request 15 - noise

8/9/2019 Request 15 - Noise

1/28

Further Information request

Item 15


2/28

Gaybrook Wind Farm

Our Ref: JR/FIR/5201

Item 15 Response Page 1

15i. The applicant shall clarify if the noise modelling took account of the effects of

prevailing winds, which may carry noise to or from a receptor, on predicted noise

levels. It is considered that in order to ensure that the EIS is complete the applicant

should demonstrate predicted noise levels at houses which are unoccupied but

habitable and sites which have outstanding planning permissions for dwellings. It is

also noted in the EIS, that wind speeds at 10 meters above ground levels were taken.

Given that the hub height of the turbines in 85 meters, it is questioned whether this

is appropriate. You are requested to address this issue.

The following response has been prepared by Mike Simms, BE MEngSc AMIOA - AcousticConsultant. IWCM Ltd commissioned Mike Simms to respond to this further information

request relating to noise.

Prevailing Winds:

The noise predictions have been prepared using the method described in ISO 9613:1996

Acoustics - Attenuation of sound during propagation outdoors Parts 1 and 2. This method is

designed to predict the noise levels at receptors as the noise propagates in the outdoor

environment. The resulting values are in terms of a downwind sound pressure level, thus they

represent the worst-case values for each receiver in terms of the wind direction.

Moreover, in certain cases, for example on the local road between the two groups of turbines,

locations cannot be downwind of all wind turbines simultaneously, thus the calculations are

conservative in this respect.

Unoccupied Houses and Houses in Planning:

Selection of the appropriate noise prediction locations was based on a detailed house survey

of the area. No unoccupied houses were identified and 2 houses with planning but not yet

constructed were included in the set of locations.

Wind speeds at 10m above ground:

The noise emission data for wind turbines are typically provided by the manufacturer relative

to the wind speed at 10m height above ground, measured according to the procedure in

IEC61400-11 Wind turbine generator systems Acoustic noise measurement techniques.

Thus, during the test, while the wind speed at 10m may have a value of, for example, 6 m/s,


3/28

Gaybrook Wind Farm



the wind speed at hub height may be 8 m/s. The noise level generated at this speed is then

recorded against the wind speed of 6 m/s at 10m height.

By way of context, the reason for the choice of 10m height is that wind data at this height can

be collected with a portable mast and as such is more easily available at an early stage in the

site selection process.

ii. With regard to noise impacts the most critical situation will be when the turbines

are operating at relatively low wind speeds at night-time, when the background

noise levels are low and the increase in background levels will be highest. The

applicant has failed to demonstrate that the increase in noise levels above normalbackground level, will be within acceptable limits and therefore you are requested to

submit a comprehensive noise study dealing with the tonal and mechanical noise

and also demonstrate whether the increase in noise above normal background level

is acceptable in the context of the aforementioned guidelines.

This response was prepared by Mike Simms,BE MEngSc AMIOA - Acoustic Consultant.

Night-time noise levels:

The DoEHLG Wind Energy Development Guidelines state that:

In general, a lower fixed limit of 45 dB(A) [LA90, 10min] or a maximum increase of 5dB(A)

above background noise at nearby noise sensitive locations is considered appropriate to

provide protection to wind energy development neighbours.

[] in low noise environments where background noise is less than 30 dB(A), it is

recommended that the daytime level of the LA90, 10min of the wind energy development noise be

limited to an absolute level within the range of 35-40 dB(A).

Separate noise limits should apply for day-time and for night-time. During the night the

protection of external amenity becomes less important and the emphasis should be on

preventing sleep disturbance. A fixed limit of 43dB(A) will protect sleep inside properties

during the night.


4/28

Gaybrook Wind Farm



In Appendix 15.1, noise survey locations A to D are shown in Figure 1. (House A was

originally selected based on the previous wind turbine layout. Two turbines which were in

this area are no longer proposed.)

In Appendix 15.2, the noise survey data from the original noise survey is reproduced with

data and night-time values presented on separate graphs. The following points are noted:

House A is now distant from the wind farm and consequently the noise levels aresignificantly lower than in other cases.

The daytime noise environments are greater than 30dB(A), thus the 45dB(A) daytimecriterion applies.

In all cases, both the daytime and night-time noise levels are within the criteria, and are

indeed within 45dB(A) by day and 43dB(A) by night, thus the background noise is not relied

upon to demonstrate compliance with the criteria.

Taking all this in account, it is considered that the wind farm as proposed complies with the

DoEHLG guidelines in respect of noise.

Tonal and Mechanical Noise

The noise predictions are based on noise source sound power levels taken from a document

supplied by the manufacturer, which details the results of a wind turbine sound test procedure

are set down in IEC61400-11 Wind turbine generator systems Acoustic noise measurement

techniques and contains the report from the independent company which carried out the test.

The test procedure involves measuring the noise levels of the wind turbine operating under a

range of wind speeds, and results in a sound power level in octave bands. In this way thetotality of the noise, i.e. the aerodynamic and mechanical components are included.

This procedure also contains a method for measuring any potential tones which may incur a

penalty in the assessment. The report finds that the tonal components of the wind turbine

noise are less than 4dB in all cases, therefore no correction applies to the calculated noise

levels.


5/28

Gaybrook Wind Farm



iii. In order to assist in the assessment of the proposal by the Planning Authority,

please submit an accurate map to suitable scale showing the location and curtilage

of all occupied and unoccupied but habitable dwellings and existing planning

permissions for dwellings within a 500m radius in the context of the turbines.

Predicted noise levels arising from the development for all sensitive receptors within

the 500m Band is hereby requested.

IWCM Ltd prepared an accurate map at a scale of 1:10,000 showing the location and

curtilage of all occupied but habitable dwellings and existing planning permissions for

dwellings within a 500m radius in the context of the proposed turbines, please refer toDrawing Pack, Figure 12 Noise Contour Map & Figure 13 Dwelling Curtilage within 500m

for full details. Predicted noise levels arising from the development for all sensitive receptors

within 500m Band was carried out as requested by Westmeath County Council. This section

should be read in conjunction with Chapter 12 Noise Impact Assessment of the EIS.

Noise predictions for sensitive receptors within 500 metres

There are 2 number dwellings located within the 500m band of the proposed development;

both dwellings are in the ownership of landowners involved in the proposed development. A

noise assessment was carried out by IWCM Ltd, using WindPRO version 2.7.468, (updated

software from WINDFARM) to assess the predicted noise levels at worst case scenario. The

assessment found that both dwellings (receptors) are within the DoEHLG guidelines of

43dB(A).

The following table highlights the predicted noise levels at dwelling (receptor) 116 and 212:

Dwelling ID WINDPro ID Predicted Noise

level

Nearest Turbine Distance

116 M 39.8dB(A) T2 459

212 BY 40.9dB(A) T8 419

Table 15.1: Predicted noise levels within 500m of a turbine


6/28

Gaybrook Wind Farm



Noise predictions for curtilages of dwellings within 500 metres

A noise assessment was carried out by IWCM Ltd, using WindPRO version 2.7.468, to assess

the predicted noise levels at worst case scenario at all curtilages of dwellings within 500

metres of a proposed turbine. There are 11 curtilages of dwellings within 500 metres of a

turbine and 1 number curtilage just over 500 metres from a turbine (511 metres). All 12

curtilages of dwellings have been assessed for noise. The assessment found that all curtilages

of dwellings are within the DoEHLG guidelines of 43dB(A). Please refer to Appendix 15.3

for full details of predicted noise levels and distances to each individual turbine.

Dwelling ID WINDPro ID Predicted Noise

Level dB(A)

Nearest Turbine Distance

117 A 38.6 1 468

116 B 40.5 2 417

115 C 39.5 2 466

114 D 39.2 2 483

163 E 40.2 5 478

162 F 38.7 5 474

240 G 38.2 7 511

181 H 38.9 7 487

209 I 39.0 6 478

210 J 40.3 6 470

212 K 41.4 8 386

211 L 39.9 9 481

Table 15.2: Curtilages of dwellings within 500 metres

Noise predictions for dwellings located within 1km of a proposed turbine

Predicted noise levels were also carried out for all sensitive receptors within 1000m (1km)

(10 rotor diameter) of all proposed turbines as the layout has changed significantly since

further information was requested under planning reference 10/5009.

The noise assessment was carried out by IWCM Ltd, using standard industry software

WindPRO version 2.7.468 to predict noise levels. Noise predictions are based on


7/28

Gaybrook Wind Farm



International Standard ISO 9613, Acoustics Attenuation of Sound during Propagation

Outdoors.

The predicted noise emission levels at noise sensitive locations from the proposed

development are detailed in Appendix 15.4. Noise predictions were carried out for the critical

wind speed of 6m/s at 10m height. The assessment found that all dwellings (receptors) are

within the DoEHLG guidelines of 43dB(A). The highest predicted noise level is 40.9dB(A)

(which is well below the excepted level of 43dB(A)) at receptor 212, this receptor is a

landowner involved in the proposed development.


8/28

Appendix 15.1

Location of Noise surveys

Figure 1: Location of Noise Survey Locations (Map not to scale)


9/28

Gaybrook Wind Farm


Item 15 Response

Measured background

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

4 19.3

5 22.1

6 26.4

7 28.8

8 29.1

9 27.7

Appendix 15.2

noise levels and predicted wind turb

Background

Noise based on

Curve Fit

dB, LA90

Planning

Criterion

dB

Differenc

dB

34.2 45.0 -25.7

37.4 45.0 -22.9

41.2 46.2 -19.77

45.1 50.1 -21.35

48.9 53.9 -24.79

52.1 57.1 -29.44

Page 1

ine noise levels

eExceeds?

No

No

No

No

No

No


10/28

Gaybrook Wind Farm


Item 15 Response

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

4 19.3

5 22.1

6 26.4

7 28.8

8 29.1

9 27.7

Background

Noise based on

Curve Fit

dB, LA90

Planning

Criterion

dB

Differenc

dB

30.3 43.0 -23.7

35.4 43.0 -20.9

40.4 45.4 -19.0

44.7 49.7 -20.9

47.6 52.6 -23.5

48.8 53.8 -26.1

Page 2

eExceeds?

No

No

No

No

No

No


11/28

Gaybrook Wind Farm


Item 15 Response

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

4 33.4

5 36.3

6 40.1

7 42.2

8 42.39 41.0

Background

Noise based on

Curve FitdB, LA90

Planning

Criterion

dB

Differenc

dB

35.1 45.0 -11.6

37.1 45.0 -8.7

39.5 45.0 -4.9

42.2 47.2 -5.0

45.1 50.1 -7.847.9 52.9 -11.9

Page 3

Exceeds?

No

No

No

No

NoNo


12/28

Gaybrook Wind Farm


Item 15 Response

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

4 33.4

5 36.3

6 40.1

7 42.2

8 42.3

9 41.0

Background

Noise based on

Curve Fit

dB, LA90

Planning

Criterion

dB

Differenc

dB

31.6 43.0 -9.6

35.8 43.0 -6.7

39.2 44.2 -4.1

42.0 47.0 -4.8

44.1 49.1 -6.8

45.6 50.6 -9.6

Page 4

Exceeds?

No

No

No

No

No

No


13/28

Gaybrook Wind Farm


Item 15 Response

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

432.8

535.7

639.6

741.7

841.8

940.5

Background

Noise based on

Curve FitdB, LA90

Planning

Criterion

dB

Differenc

dB

35.3 45.0 -12.2

37.1 45.0 -9.3

39.0 45.0 -5.4

41.0 46.0 -4.3

43.0 48.0 -6.2

45.1 50.1 -9.6

Page 5

Exceeds?

No

No

No

No

No

No


14/28

Gaybrook Wind Farm


Item 15 Response

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

432.8

5

35.7

639.6

741.7

841.8

940.5

Background

Noise based on

Curve Fit

dB, LA90

Planning

Criterion

dB

Differenc

dB

27.6 43.0 -10.2

31.2 43.0 -7.3

34.9 43.0 -3.4

38.2 43.2 -1.5

40.8 45.8 -4.0

42.2 47.2 -6.7

Page 6

Exceeds?

No

No

No

No

No

No


15/28

Gaybrook Wind Farm


Item 15 Response

Wind speedm/s

Wind Turbine

Noise at House

dB, LA90

433.9

5

36.8

640.7

742.7

842.8

941.5

Background

Noise based onCurve Fit

dB, LA90

Planning

Criterion

dB

DifferencdB

36.9 45.0 -11.1

37.0 45.0 -8.2

37.2 45.0 -4.3

38.0 45.0 -2.3

39.4 45.0 -2.2

41.7 46.7 -5.2

Page 7

Exceeds?

No

No

No

No

No

No


16/28

Gaybrook Wind Farm


Item 15 Response

Wind speed

m/s

Wind Turbine

Noise at House

dB, LA90

433.9

536.8

640.7

742.7

842.8

941.5

Background

Noise based on

Curve Fit

dB, LA90

Planning

Criterion

dB

Differenc

dB

28.1 43.0 -9.1

29.3 43.0 -6.2

31.2 43.0 -2.3

33.6 43.0 -0.3

36.7 43.0 -0.2

40.6 45.6 -4.1

Page 8

Exceeds?

No

No

No

No

No

No


17/28


18/28

Gaybrook Wind Farm


Appendix 15.3

Noise Predictions for Curtilages of dwellings within 500m


19/28


20/28


21/28


22/28

Gaybrook Wind Farm


Appendix 15.4

Noise Predictions levels within 1km of a turbine


23/28


24/28


25/28


26/28


27/28


28/28

request 15 - noise

Documents