Strange voice comes through COD whilst on the main menu!

So me and my friends were in a private party (locked so our not so good friends can join and ruin our K/D :') ) we were all pretty silent, i was looking at my load outs when a strange voice with much more clarity suddenly speaks saying one of our friends gamer tags! So i know this isn't a randomer joining and leaving as there is no sound to indicate any one joining or leaving. MY own voice isn't recorded  in the video so it only leaves 2 of my friends who you can hear from the video it just clearly wasn't.