i had an annoying tick , couldnt for the life of me figure it out ,
turned out it was the magnet for the computer tapping the receiver at higher speeds as it twisted round on the spoke wee drop of superglue fixed it ,
on another occasion it turned out to be the toggle off my jkt hitting seat post ,
only discovered after riding along with an ear cocked up for about 2 miles trying to locate the source of the noise .