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
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.
For the same reason that your phone’s microphone doesn’t pick up the person you’re talking to’s voice and send it back to them even when you’re on speaker phone…all modern phones have a cancellation circuit that basically subtracts anything they’re putting out via their speaker from whatever they’re getting in via their microphone. This makes sure the microphone only picks up external noises, not things the phone itself is generating.
If you use any *other* speaker the other person will hear it, beause the phone doesn’t know what’s coming out of that other speaker and it can’t filter that out. But your phone uniquely knows what’s coming out of it’s own speaker so it can ignore that when it comes back in via the microphone.
This is not the same as noise-cancellation, that’s designed to cancel out external noises.
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