Just make some sounds, and see how the graph changes; you can hover over a dot with your mouse to see it's value/volume on the graph (make sure to hover over the right spot) I recommend full volume microphone
Make sure to give permission to Scratch for access to your Microphone! This took about an hour; the concept is quite simple, I only used 1 sprite, 9 scripts, and 54 blocks. You can "see inside" to look at how it works
