4 layers67.5 × 9.2 mm

Ref mic
loudifier/OpenRefMic
open hardware design for a high-performance low-cost measurement microphone
47 parts169MIT
Printed circuit boards designed in KiCad and published on GitHub, each with its parts, layers and size, its README and its files; open any of them in PCBKit.

loudifier/OpenRefMic
open hardware design for a high-performance low-cost measurement microphone