IEC 61400-11:2012

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

IEC 61400-11:2012 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.