Creating sound immission mimicking real-life characteristics from a single wind turbine

This paper describes a method to synthesise wind turbine sounds to be used in sleep studies using a parameter-based synthesis. The parameter values were determined using recordings of several types of operating wind turbines, thorough investigations of the recorded sounds, previous reports on wind turbine sound characteristics, and acoustic knowledge on how sound properties change from source to an outdoor receiver. The different wind turbine types are shown in the paper to have characteristic amplitude modulation (AM) spectra, with different AM strengths in different 1/3 octave bands. The statistical levels of the AM are evaluated and the correlation between A-weighted AM and AM in individual 1/3 octave bands is evaluated using linear regression. Method tests of the proposed synthesis technique show that it performs well and that wind turbine sound signals that include arbitrary AM spectra can be created. The work was part of the research project WiTNES (Wind Turbine Noise Effects on Sleep).