If anyone wants to try a demonstration of sonar on their own laptop and learn how it works along the way by coding part of it, one of the classes I took and later graded labs for has a Jupyter notebook you can download for Lab 1: Laptop Sonar here: https://inst.eecs.berkeley.edu/~ee123/sp18/labs.html

It is an assignment but I promise it’s fun :)

You’ll want to have the appropriate anaconda installed for python 2.7 to be able to run it, and pyaudio.

edit: clarification

Some previous discussion here https://news.ycombinator.com/item?id=17916200