David, A. Thorne, R. Stand-off Distances From a Wind Farm
An Underpinning Methodology to Derive Stand-off Distances from a Wind Farm
20th International Congress on Sound and Vibration, (ICSV20) Bangkok, Thailand
Antoine David, Robert Thorne
This paper proposes a methodology to assess the effect of wind turbine low frequencies and infrasonic frequencies on nearby human receptors. The method includes objective calculations and subjective responses. Thresholds for detection of low frequency and infrasound, annoyance and physiological effects are proposed. The interactions of several wind turbines will result in complex sound fields given the different effects involved such as harmonics generations, directivity of the sound field, difference in rotational speed between wind turbine, interference, beating effects and modulation may result. The diurnal effect temperature inversion, variability in wind speed, will add to the complexity in the assessment of the impact of low frequency and infrasound. Modulation of low-and infrasonic frequencies is influenced by the interaction of several wind turbines. Frequency analysis measured in the presence of wind turbines has three separate components: (a) the basic blade rate infrasound, (b) a secondary unsteady component of blade lift induced noise, and (c) the broadband ambient from turbine and wind-flow noise. The propagation of sound for low frequency and infrasonic frequency has been reviewed and the slope for the attenuation of sound below 100Hz is proposed to range from 14.3Log(R) to 12.4Log(R) when a temperature inversion takes place.