From The Action Lab , and Action Lab Shorts.

Links to some of the visuals in this video:
https://www.jezzamon.com/fourier/

Cochlear and Audible Frequency

https://en.wikipedia.org/wiki/Cochlea
https://www.physicsclassroom.com/html-module/wave-addition/1/WaveAdd.html
https://phet.colorado.edu/sims/html/fourier-making-waves/latest/fourier-making-waves_all.html
https://academo.org/demos/wave-interference-beat-frequency/
https://www.youtube.com/watch?v=y7yN6QtedHc