I've put 5 EM172 microphones close together and measured there signal and coherence. They are plugged in to accelerometer channels.

Then I've suspended microphones around the MC - 2 at MC2, 2 at MC1,3 and 1 at PSL. The amplifier box is above STS readout box.

Microphone close to PSL gave a strong coherence with MC_F, as we already saw it using Blue Bird Microphone.

ACC_MC2_XY channels <=> MC2 microphones

ACC_MC1_XY channels <=> MC1,3 microphones

ACC_MC1_Z channel <=> PSL microphones