annpyong sound echo

[wesamaz]

I have a problem when I call2 windows extensions , I hear an annoying sound echo, what cause that?

 

[leejor]

It can be a number of things. Generally it is because your voice is too loud, is reaching the far end, overcomes echo suppression, then returns, with a slight delay. I have seen this happen when users are on a headset that is boosting the callers voice. Is this happening on external calls as well?