Here are the data structures with brief descriptions:

CMicrophone_PDM	Class for using the hardware PDM (pulse-density modulation) audio decoder on RTL872x and nRF52 devices
CMicrophone_PDM_Base	Class used for settings. You will not instantiate one of these; it's a base class of Microphone_PDM_MCU
CMicrophone_PDM_BufferSampling	Class to configure buffer sampling mode
CMicrophone_PDM_MCU	Microphone_PDM_MCU is an alias for the MCU-specific class like Microphone_PDM_nRF52
CMicrophone_PDM_nRF52	MCU-specific implementation of PDM for the nRF52
CMicrophone_PDM_RTL872x	MCU-specific implementation of PDM for the RTL872x