That annoying echo you sometimes hear in your cell phone, VoIP (Voice over Internet Protocol) connection or land-line phone could have many causes, and there are solutions to get rid of it. Echo is usually only heard by one of the users on the phone call.
Where It Comes From
The sound from the microphone in the mouthpiece of your phone can loop back into the phone's earpiece, causing the caller to hear an echo of his own voice. This loop back is often intentional, allowing the caller to hear herself as she speaks, but it becomes a problem when there is a time lag. The echo can also be caused by the sound transmission bouncing back from the recipient's phone or by the sound on the recipient's phone being too loud, causing the received audio to enter the microphone on the mouthpiece of the recipient's phone.
What Causes It
Line echo, also called hybrid or electric echo, is caused by the phone wiring when the signal is returned to the caller rather than ending with the recipient. This happens because the signals aren't separated properly, the line is "unbalanced," or there is a problem with the line, such as water damage or twisted wire. It can also be caused by network hops, which is when the transmission signal jumps between lines to reach its destination. This causes a delay in the signal, which can create a delay in the side tone, or the transmission of the caller's voice to his earpiece.
How to Fix It
Most phone system operators employ echo cancellation equipment to reduce the possibility of an echo, but there are a few extra steps you can take to eliminate the echo. You can ask the person you are calling to turn down the volume on her phone. You can also hang up the phone and call the person back to get a better transmission. Try taking the phone off the speaker phone setting. Alternatively, try moving from the area where you are experiencing the echo, as it may be caused by sound bouncing off of objects in the room.