Design and Access Statement Site: Broad Marsh Chalet, NR17 1LN

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Design and Access Statement Site: Broad Marsh Chalet, NR17 1LN Appendix B - Noise Report: Windcrop HY-5 Acoustic Impact Assessment of Small Wind System Installation Introduction The Windcrop HY-5 is designed to minimise noise generation. Wind generator noise issues in the past have chiefly arisen from either mechanical gearbox noise or aerodynamic noise. The Windcrop HY-5 generator is a direct drive system and has no significant sources of mechanical noise. The Windcrop HY-5 generator blades are specifically designed to minimise aerodynamic noise. To achieve this, the rotor is designed to operate at unusually low speed, with a nominal blade tip speed of 70.3m/s. The blades vary in twist and chord along their length to maximise efficiency and thus minimise noise. In particular, the blade chord has been kept as small as is practicable near the tip. Also the blade tips themselves are carefully shaped specifically to minimise noise. Measured Noise Levels The Windcrop HY-5 is currently undergoing noise testing as part of the overall testing requirement for its accreditation under the Micro generation Certification Scheme (MCS). The relevant testing standard is MCS006 - Micro and Small Wind Turbines, which references the BWEA Small Wind Generator Performance and Safety Standard (29 February 2008). Noise testing and assessment procedures and criteria are detailed in Section 3: Acoustic Sound Testing and Appendix A: Notes on the Use of Noise Label Information. The provisional BWEA Reference Sound Levels at 25m and 60m at an 8m/s hub height wind speed are: Lp, 25m = 52.5dB(A) Lp, 60m = 45dB(A) The location of the property and the generator is such that the nearest neighbour is in excess of 135m distant. It is anticipated that the generator’s noise performance will satisfy the standards and will not impact neighbouring properties. Testing on a comparable installation, mounted on a 15m pole achieved a noise immission of below 45dB(A) at any point greater than 50m from the installation at wind speeds up to 8m/s or Force 5. Above these wind speeds, the noise from the surrounding trees and buildings would be much greater than that from the generator. Recommended Good Practice on Controlling Noise from Wind Turbines From ‘The Assessment and Rating of Noise from Wind Farms’ (ETSU-R-97). The current practice on controlling wind farm noise by the application of noise limits at the nearest noise-sensitive properties is the most appropriate approach. Noise limits should be applied to external locations and should apply only to those areas frequently used for relaxation or activities for which a quiet environment is highly desirable. Page | 16
Design and Access Statement Site: Broad Marsh Chalet, NR17 1LN Noise limits set relative to the background noise are more appropriate in the majority of cases. Generally, the noise limits should be set relative to the existing background noise at the nearest noise-sensitive properties and the limits should reflect the variation in both turbine source noise and background noise with wind speed. It is not necessary to use a margin above background noise levels in particularly quiet areas. This would unduly restrict developments that are recognised as having wider national and global benefits. Such low limits are, in any event, not necessary in order to offer a reasonable degree of protection to wind farm neighbours. Separate noise limits should apply for day-time and for night-time as during the night the protection of external amenity becomes less important and the emphasis should be on preventing sleep disturbance. Absolute noise limits and margins above background should relate to the cumulative effect of all wind turbines in the area contributing to the noise received at the properties in question. Any existing turbines should not be considered as part of the prevailing background noise. Noise from the wind farm should be limited to 5 dB(A) above background for both day- and night-time, remembering that the background level of each period may be different. The L A90,10min descriptor should be used for both the background noise and the wind farm noise, and when setting limits it should be borne in mind that the L A90,10min of the wind farm is likely to be about 1.5-2.5 dB(A) less than the L Aeq measured over the same period. The use of the L A90,10min descriptor for wind farm noise allows reliable measurements to be made without corruption from relatively loud, transitory noise events from other sources. A fixed limit of 43 dB(A) is recommended for night-time. This is based on a sleep disturbance criteria of 35 dB(A) with an allowance of 10 dB(A) for attenuation through an open window (free field to internal) and 2 dB(A) subtracted to account for the use of L A90,10min rather than L Aeq,10min . Both day- and night-time lower fixed limits can be increased to 45 dB(A) to increase the permissible margin above background where the occupier of the property has some financial interest in the wind farm. In low noise environments the day-time level of the L A90,10min of the wind farm noise should be limited to an absolute level within the range of 35-40 dB(A). The actual value chosen within this range should depend upon: the number of dwellings in the neighbourhood of the wind farm, the effect of noise limits on the number of kWh generated, and the duration of the level of exposure. For single turbines or wind farms with very large separation distances between the turbines and the nearest properties, a simplified noise condition may be suitable. If the noise is limited to a L A90,10min of 35 dB(A) up to wind speeds of 10 m/s at 10 m height, then this condition alone would offer sufficient protection of amenity, and background noise surveys would be unnecessary. Page | 17
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Design and Access Statement Site: Broad Marsh Chalet, NR17 1LN

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