The sensing device is a MEMS microphone that outputs a pulse density modulated (PDM) signal. There are chips available to directly interface such a microphone to a USB port, but [Mahesh] found ...

Deciding to go for a full digital design for the circuitry, the peripheral is based off of a MEMS microphone and an STM32 microcontroller doing the heavy lifting between it and a USB connection.

Knowles and Infineon dominate the market for microelectromechanical system (MEMS) microphone chips. Knowles of the U.S. in 2013 was the biggest supplier of packaged MEMS microphones ready for assembly ...