We noticed a small bump in DARM at about 360 Hz, coherent with PRCL. We added a 270-430 Hz elliptic band-stop. DARM improved and the coherence is almost gone. We are losing 9 degrees of phase at 50 Hz (PRCL UGF).
The filter is implemented in the SUS filter bank.
The bandstop filter is now engaged by the guardian in the NOISE_TUNING step.