Results of two-channel simultaneous audio recordings outdoors in the free field and inside a bedroom are presented from the Leonards Hill wind farm that has two Repower 2MW MM82 wind turbines, which are approximately 700m from the dwelling.
The analysis demonstrates the dynamic effects of amplitude modulation on attenuation of sound between the two measurement locations and shows how outdoor to indoor attenuation is compromised at particular room resonant modes.
Different measurement approaches are discussed with the conclusion that a 10Hz sampling rate of sound level is insufficient to accurately determine peak to trough amplitude modulations.
Infrasound measurements are also presented from the Lake Bonnie wind farm in South Australia to show that amplitude modulation is also observable below 20Hz and that low frequency infrasound may also be considered to be amplitude modulation.
Accepted for presentation at Institute of Acoustics meeting, WIND TURBINE NOISE – “AM, AND WHERE TO NEXT FOR ETSU-R-97?”, Newport, Wales, 20 March 2014
This article is the work of the author(s) indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.