I'm a year late to help here, but I think he meant clear-cursor.ogg which I personally really disliked hearing as well, from the moment it was added in 1.0. When I saw this mod I immediately looked into it to specifically see if it was included. It's a strangely too-quiet and harsh, echoey sound effect that gets on my nerves far more than it should. I don't think I'm fussy either; this is the only sound I even want to remove.
I think I dislike it because it signals an action that is doing 'literally less-than-nothing' with something that sounds important and 'physical', and is at the same time so quiet that it sounds like it comes from outside the game. I kinda want to submit a suggestion for changing it on the forums to see if anyone else feels the same.