eli5: How can you play something out of your phone speaker while you’re on a call(with someone on speakerphone), and the person on the call can’t hear it at all?

Question

eli5: How can you play something out of your phone speaker while you’re on a call(with someone on speakerphone), and the person on the call can’t hear it at all?

In: 6

Answer 1

because neither the speaker nor the microphone have perfect all around radiation/pickup.

they play/listen past each other.

there’s maybe also some noise cancellation going on, with the microphone knowing what the speaker plays and filtering it out. but i dont know if that is actually done.