Although there's not much left of the original code ( see previous version https://youtu.be/5x1vaUg5-CI ), it was heavily inspired by this project:

https://github.com/G6EJD/ESP32-8266-Audio-Spectrum-Display By @G6EJD

Source: https://github.com/tobozo/ESP32-8-Octave-Audio-Spectrum-Display/tree/wrover-kit

Hardware used:

• ESP32 ODROID-GO
• Electret Microphone Breakout