Effect of infrasound on the detectability of amplitude-modulated tonal noise

Abstract

This study investigated aural detectability of wind farm infrasound and its effects on higher frequency audible tonal noise via creating a sensation of amplitude modulation. The study focused on infrasound pulses with a fundamental frequency at 0.8 Hz and 46 Hz tone which was amplitude modulated at 0.8 Hz. That tone had an amplitude modulation depth between 2 and 12 dB and tonal audibility between 5 and 17 dB. The wind farm noise (WFN) samples were selected from long-term indoor measurement data and were played at an average of 30 dBA or 62 dBG. Forty-eight participants were recruited from four different demographic groups among which some were sleep disturbed by WFN. Participants did not detect the infrasonic content of wind turbine noise above chance, either when analysed in separate groups or overall and this is consistent with previous research. Infrasound reduced the probability of amplitude modulation detection by 2.8% (95% confidence interval 0.2 to 6.1), indicating that inaudible infrasound has a small effect on the audibility of low frequency tonal noise.