The Relationship between LA90 and LAeq Wind Turbine Sound Level Descriptors in NZ

Lindsay Hannah , Wyatt Page , Stuart McLaren

New Zealand Acoustics, 25(3), pp.4- 13 . (2012).

The New Zealand Wind Turbine Standard NZS6808 provides guidance on the methods for the prediction, measurement and assessment of sound emissions from wind turbine generators. This study attempted to quantify the potential variability between measured wind turbine generator sound emissions using the descriptors LAeq and LA90 [specified in the standard], both on the wind farm site [near-field] and at a remote receiver dwelling location [far-field] where people reside. Results of the field study showed that the mean sound level difference between the descriptors, measured at a residential location remote from the wind farm was 2.4 dB compared to 1.4 dB on the wind farm site. Of the 11,150, 10 minute sound pressure level sample pairs recorded over a 12 month period at the remote location, only 39 remained for the analysis after post-filtering to remove samples contaminated by extraneous noise. The study illustrates the difficulty in making robust measurements of wind turbine sound in the far-field.