Yep! If you want to try this, you can plug any speaker with a 3.5 mm output into a mic input and speak into it. It'll probably be faint, but it usually works.
Microphone-less headphones are a great way to test this phenomenon. If you have them handy, just plug them into the mic port and talk. IIRC only one earpiece in a stereo set connects with a mono microphone jack.
https://security.stackexchange.com/questions/154343/can-a-sp...