Since last night, there have been a few unlock correlated to noise glitches in the NEB (see the logbook entry https://logbook.virgo-gw.eu/virgo/?r=63540 for their first description), I stopped the NCals at 9:09 UTC to double check that they were not the source of the noise. The attached plot is showing the noise measured with one of the NCal microphone, that is well correlated with the lock lost. The glitches continue even when the NCal are stopped (see the NCal frequencies on the bottom plot). They are even more frequent.

The NCals have been restarted at 17:50 UTC.

As a curiosity, the attached file is playing 20 second of the glitches starting from 11:25:12 UTC (1394623530)