This could be old info but I believe the Baseband chipset has its own microphone in addition to access to the user mics for the purposes of signal processing.

This could be old info but I believe the Baseband chipset has its own microphone in addition to access to the user mics for the purposes of signal processing. This was a stink years ago and part of the GSMK product development. AFAIK GSMK is the only commercially available product to have a baseband firewall and their own stuff running to deal with this