EN 61400-11:2013

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and units
5 Outline of method
6 Instrumentation
7 Acoustic measurements and measurement
  procedures
8 Non-acoustic measurements
9 Data reduction procedures
10 Information to be reported
Annex A (informative) - Other possible characteristics
        of wind turbine noise emission and their
        quantification
Annex B (informative) - Assessment of turbulence
        intensity
Annex C (informative) - Assessment of measurement
        uncertainty
Annex D (informative) - Apparent roughness length
Annex E (informative) - Characterization of a secondary
        wind screen
Annex F (normative) - Small wind turbines
Annex G (informative) - Air absorption
Bibliography
Annex ZA (normative) - Normative references to
         international publications with their
         corresponding European publications

IEC 61400-11:2012(E) presents measurement procedures that enable noise emissions of a wind turbine to be characterised. This involves using measurement methods appropriate to noise emission assessment at locations close to the machine, in order to avoid errors due to sound propagation, but far away enough to allow for the finite source size. The procedures described are different in some respects from those that would be adopted for noise assessment in community noise studies. They are intended to facilitate characterisation of wind turbine noise with respect to a range of wind speeds and directions. Standardisation of measurement procedures will also facilitate comparisons between different wind turbines. This new edition constitutes a technical revision, introducing new principles for data reduction procedures.