Make a Simple Microphone Out of a Matchbox and Graphite Pencil.
Microphones may seem like a daunting technology, but making your own microphone isn’t difficult at all. You can build a simple microphone from a number two pencil and a tiny graphite matchbox.
You’ll need a few more things to complete the project – like a 9-volt battery, some main wires, crocodile leather clips, and a speaker or a pair of headphones – but this build from YouTuber DaveHax is insanely simple. Just gently remove the graphite from the pencils, scrape the flat side off each piece, place them in the matchbox as shown in the picture, and you’re ready to wire everything up. It may not be as good as a studio mic, but it works surprisingly well!
How to make a microphone from a matchbox | DaveHux