After a quick coherent hunt between OPO frequency noise and PEM channels it seems that a lot of noise came from SQZT6 and ISCT6 table (2nd and 3rd row, 3rd column). Both ISCT6 and SQZT6 accelerometer shows highest coherence at ~1kHz compared to accelerometers and microphones everywhere else in the LVEA (along PSL fiber path). ISCT6 accelerometer also shows high coherence at ~300Hz (2nd row, 3rd column). Still unclear where the noise comes from, but it's probably safe to assume that whatever noise is giving us trouble they're all local to HAM6 area.