system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: when my phone is connected to my cars audio system via Bluetooth, how does the person talking not hear themself through my speakers?
gpt
Your car stereo uses active echo cancellation. It know what signal it's sending out of the speakers so it compares the signal it's picking up on the mic to the signal it's send out the speakers and tries to remove anything that is the same in both.

This is the same technology that works on your cell phone and on modern table stop speaker phones.