system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do two phones in the same room make weird sounds when on a live call?

Sometimes even if only one of the phones’ mic is on.
gpt
This is called feedback and is similar to what happens if you put live microphone near a speaker connected to it.

Microphone on one phone picks up a sound, then the other phone plays that sound and the first phone picks it up again and amplifies it in an continuous loop ultimately causing a high pitched noise.