Perception of low frequency components in wind turbine noise

Wind turbine noise is a new environmental noise problem caused by the development of wind power generation. This problem has often been discussed as a low frequency noise issue and the psychoacoustic and health effects of low frequency components are an important matter of controversy. As a study related to this problem, the authors have conducted a series of laboratory experiments using a test facility capable of reproducing sounds of low frequencies down to infrasound. Three auditory experiments conducted to investigate the human auditory sensation of low frequency components contained in wind turbine noise are reported in this paper. In the first experiment, the audibility of low frequency components of wind turbine noise was examined by changing its spectrum characteristics by applying low-pass filtering with ten different cutoff frequencies from 10 to 125 Hz. In the second experiment, the hearing thresholds for sounds containing dominant components at low frequencies were tested by changing the width of the frequency band in seven steps and the critical spectral characteristics in 1/3-octave-bands for the hearing threshold are investigated. In the third experiment, a loudness test was performed using an artificial noise modeling general wind turbine noises, in which the frequency characteristic of the test sound was changed by applying high-pass filtering with nine different cutoff frequencies from 16 Hz to 1 kHz. Based on the results of these experimental investigations, the suitability of single-number indices for the assessment of wind turbine noise is discussed.