[Obayashi (Aogaku), Yuzurihara]

This is a follow-up analysis of klog34679 by Miyoki-san.

We looked for the coincident fluctuation of the breathing of the sensitivity around 60Hz and found that it can be seen in Gauch. Sometimes, we can see the non-Gaussian feature in 60~100 Hz. So, we doubted this is related to the breathing around 60Hz.
To investigate the cause, we checked the K1:OMC-TRANS_DC_A_IN1_DQ. At first, we tried to several ranges of bandpass filters in 10~80 Hz, and found the bandpass of 20 to 60 Hz provides the good signal visualization. We listed up the time of excess in the data after applying the bandpass filter of 20~60Hz and whitening.

The example plots are attached. The top panel shows the K1:OMC-TRANS_DC_A_IN1_DQ after the signal processing. The red dotted line indicates the excess time. The bottom panel shows the time-frequency map showing the non-Gaussian feature. The some of excess times are coincidence with the time of non-Gaussian feature in Gauch.

As can be seen in the timeseries plot, the excess shape looks like the damping signal. So, I wonder a excitation of peak(s) around 60 Hz is the cause. The long tail of the excited peak covers the frequency band of 60~100 Hz (which can be seen in Gauch) and also behaved like breathing of the sensitivity around 60Hz.