A PDM (Pulse Density Modulation) microphone module is an electronic device that converts sound signals into digital signals. It uses a condenser microphone to convert sound waves into an electrical signal, which is then converted into a digital signal using the pulse density modulation technique.

The resulting digital signal can be easily processed by a microcontroller or digital signal processor (DSP) for use in a variety of applications, such as sound recording devices, communication systems, electronic musical instruments, voice control systems, and more.

PDM microphone modules are popular due to their low cost, high sound quality, and ability to work with common microcontrollers and digital signal processors. Additionally, their compact design and low power consumption make them ideal for use in mobile devices and other portable electronic products.