We investigated the acoustic noise in PMC.
This work was performed without changing the air controls to keep the current environment and finished within 20 minutes.
1. Local acoustic injection
We injected 300Hz sound from my smartphone near the MIC1 (near PMC), MIC2 (near the electric rack), and MIC3 (near the mini rack for PEM), respectively.
In any case, the PMC_PZT signal was also excited at 300Hz and it was the largest ar near the PMC.
2. Position dependence of the coherence between PMC and MIC
We monitored the coherence between PMC and MIC2 with changing the MIC2 position. (Exponential mode in diaggui, not saved)
When MIC2 was located near the PMC, the coherence became larger.
But When MIC2 was located near the sound sources (some devices), the coherence became smaller.
From 1. & 2., we can conclude that the PMC is certainly sensitive to sound, but the environmental sound is not dominant compared to the sound from PMC itself.