with Daniele, we placed the accelerometer on top of the fiber amplifier box which is inside the housing.
the goal was to try to detect a correlation with some possible accoustic noise coming from the bubbles of the water, cooling the amplifier box baseplate.

we monitored a long trend of the transmission which is perturbated when high frequency noise arises, and the accelerometer signal.
the long trend plots only the peak-peak value of a full 1 second acquisition every 2 seconds during ~2500 pts equivalent to ~5000 seconds = 1h20

on the plot, the top white signal is the transmission pk-pk and the bottom red signal is the accelerometer pk-pk.
we don't see any correlation except at 600-700 pts because Daniele entered the bunker and slightly knock on the bottom of the optical table several times.
and at 1950-2300 pts, because he opened the housing (much more noise recorded by the accelerometer) and then it close it again.

he also try to knock on the amplifier controller rack which is placed on the ground, below the table, but he didn't see any correlation with some cavity lock losses.

=> no clear conclusion.
except that the noise seen on the transmission when the housing is open is close to the "high frequency noise" we observe... could it be some accoustic noise coming from elsewhere ?