Operating and wind data of WT 2 for 2022/04/21 with the respective ground motion and acoustic spectrograms for frequencies up to 150 Hz showing the presence of AM of multiple tones, which can be identified by horizontal lines around the carrier tones (57.8 Hz and 133 Hz) spaced at the BPF. The red-dashed lines in (a) indicate the end and start of the time windows used for the spectra shown in Figure 10. (a) Operating data of WT 2, (b) wind data of WT 2, (c) ground motion spectrogram outside WT 2 and (d) sound pressure spectrogram WT 2.