Example of a 30 min measurement made on 20 May 2022. (a) Spectrogram of power spectral density. (b) Azigram without a threshold. (c) Azigram showing only the bearings for the data points in (a) that are > 70 dB. The 70 dB is chosen for visualization purposes. The white color denotes the non-visualized bearings. (d) Bearing distributions of the frequencies 440–449 Hz without applying a threshold to the azigram. The boxplots in (d) show minimum, 25th percentile, median, and 75th percentile. In (a) (b) and (c), the x-axis is time (HHMMSS) and the calculation parameters are shown in Table 1.