Book 14, Question 117
Why Do You Sometimes Hear Your Own Voice Echo on a Phone Call?
You hear your own voice echo on a phone call because your words make a round trip! They travel to your friend, come out of their speaker, and get picked up by their microphone. Then they travel back to you a moment late.
More fun facts
- Hearing your own voice come back as a delayed echo on a phone call is called talker echo.
- It happens when your voice signal reflects back along the path, for example where two kinds of phone lines, called 4 wire and 2 wire, are joined.
- It can also happen when sound from the other person's earpiece or loudspeaker leaks back into their microphone.
- How annoying the echo is depends on both how long the delay is and how loud the echo is.
- When your voice comes back with almost no delay, it is called sidetone, and it does not sound like an echo.
- Devices called echo cancellers keep estimating the echo path and try to remove the echo from what you hear.
- Older international phone guidelines recommended echo control on connections where the one way echo path took longer than 25 milliseconds.
Questions kids ask
Why does echo happen more on speakerphone?
The loudspeaker is close to the microphone, so more sound can leak back in.
How can I stop an echo?
Ask the other person to turn down their speaker or use headphones.