My Teensy 4.0 with two Audio Shield (Rev D) boards to build an Active Noise Cancellation electronic subsystem for my final degree thesis.
The main scheme used for the code is the one showed below:
If you want to follow more information about this project, you can read some issues at this pjrc forum link:
https://forum.pjrc.com/index.php?threads/teensy-4-0-audio-shield-line-in-microphones.75662/