Nationwide field measurements of wind turbine noise in Japan

Abstract

A study program titled "Research on the evaluation of human impact of low frequency noise from wind turbine generators" has been performed in the past three years from the 2010 fiscal year sponsored by the Ministry of the Environment, Japan. In this study, noise measurements have been performed in immission areas of 34 wind farms across Japan. For the survey, measurement instrumentation was contrived in order to cover the low frequencies including infrasound and measurement techniques were investigated in order to detect wind turbine noise in ambient environmental noises. Each field measurement was performed for continuous 120 hours by unattended method and the sound pressure signal was recorded on the specially manufactured sound level meter. From the recording, A-, C-, and G-weighted and 1/3 octave band sound pressure levels were obtained during the time when the wind turbines were under the rated operation condition. The swishing sound, the most serious problem in wind turbine noise, was also analyzed by putting emphasis on the modulation period and sound pressure level fluctuation. In parallel with the measurements around wind farms, 18 control areas without wind turbine noise were chosen and the environmental noise was also measured for comparison.