Use an electret microphone to light a series of LEDs in proportion to volume
This is a quick prototype of a circuit I’ve seen for sale as a DIY parts kit.
In the standard configuration, all LEDs light up together, but brightness is proportional to detected sound volume.
LEAP is my personal collection of electronics projects - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting.
Projects are often inspired by things found wild on the net, or ideas from the many great electronics podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know or send a pull-request.
NOTE: For a while I included various scale modelling projects here too, but I've now split them off into a new repository: check out LittleModelArt if you are looking for these projects.