yesterday morning around 9LT profiting of ITF at LN3 and nobody working, we attempted an acoustic injection in SIB2. But right away the ITF unlocked. The unlock happened just 2 seconds after issuing the driving signal to the DAC and the loudspeaker. The signal was still ramping up and the level of acoustic/seismic noise produced (according to SIB2 accelerometer, EIB microphone) was negligible.

At that time people was working inside the trucks garage (locale camion), although we do not see any seismic burst coincident with the unlock.

Investigating further with the help of Julia we found out that a likely cause of the unlock was the onset of a large oscillation of the SSFS correction: Figure 1.

One suspect is that this could have been somehow triggered by an EM spike in the DAC signal cable that lays very close to the rampeaut board in IER.

ASAP one test we want to do is to repeat the injection having the loudspeaker unplugged.

Today around 15:20 UTC, while the ITF was in LN3,  we repeated the injection with the loudspeaker UNPLUGGED. We sent the same kind of noise through the DAC to the (unplugged) loudspeaker. The ITF did not unlock neither sensed any disturbance. We should conclude that there is no EM interference when we send the signal to the loudspeaker, but instead maybe the unlock we observed on Nov 15 was associated to the (very little!) sound and vibration we produced. This has to be tested replugging the loudspeaker and injecting real sound in the SIB2 area.