Thorne, R. The Problems With “Noise Numbers” for Wind Farm Noise Assessment

Bob Thorne, Noise Measurement Services Pty Ltd. Queensland, Australia

The Bulletin of Science, Technology and Society, August 2011


Human perception responds primarily to sound character rather than sound level. Wind farms are unique sound sources and exhibit special audible and inaudible characteristics that can be described as modulating sound or as a tonal complex.

Wind farm compliance measures based on a specified noise number alone will fail to address problems with noise nuisance.

The character of wind farm sound, noise emissions from wind farms, noise prediction at residences, and systemic failures in assessment processes are examined. Human perception of wind farm sound is compared with noise assessment measures and complaint histories.

The adverse effects on health of persons susceptible to noise from wind farms are examined and a hypothesis, the concept of heightened noise zones (pressure variations), as a marker for cause and effect is advanced. A sound level of LAeq 32 dB outside a residence and above an individual’s threshold of hearing inside the home are identified as markers for serious adverse health effects affecting susceptible individuals.

The article is referenced to the author’s research, measurements, and observations at different wind farms in New Zealand and Victoria, Australia.

Read the complete article at the National Wind Watch website: