The design uses the ESP32-WROVER primarily because of its large memory capacity. 

The MIC is an INMP441, and data is directly obtained via I2S. 

There is a button for user operation and an RGB LED to indicate status. 

There is a TF card slot, which is not part of the original functionality because the TF card consumes a lot of power; it is included only for debugging audio data. 

The battery uses a PH2.0 connector to facilitate the use of different solutions. 

The PCB has a diameter of 4 cm and includes a slot for the ESP32 antenna.

The current hardware cost of the solution is approximately $6 (excluding the battery).

Since the PCB has not been verified yet, a public link for the schematic diagram generation has not been created. After the verification is completed, the schematic diagram and PCB address will be filled in the project.