Eli5: Why do we notice a delay on a call when looking at the other person but not when we can’t see them?

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If I’m looking at someone and call their phone there is an obvious delay and it’s weird, if I’m driving or otherwise talking to someone not with me the delay isn’t noticeable, why is that?

In: Technology

2 Answers

Anonymous 0 Comments

There’s always that delay in a phone call, if the person isn’t in your line of sight your brain just doesn’t have any other data. When you can see your friend’s lips move and the sound is out of sync, your brain says “Dude, that’s weird…”

Anonymous 0 Comments

It’s like latency in audio recording.

The “source” on the other end of the line is initiating conversation – if you can see them and hear them, the signal path is voice through air (at the speed of sound) to you as the “receiver”.

The technology is quick but not that quick. The source speaks – the technology converts sound to digital data, transmits data, receives data, decodes data into audio, generates sound, sound to receiver.

If you can’t see them – you just hear the voice and are unaware of how delayed it is. Your voice is likewise delayed to them (which may seem like it would be further out of sync) but the equal delay and the fact that you only hear your voice in real time and not the temporal version that the listener hears. A delay of under 20ms is fairly benign but anything over that is very distracting and hearing it interrupts your thought process if you’re speaking and listening at the same time.