This achievement will unlock once 60 of the 240
riddler challenges have been solved
Once you unlock the secrets of the map then the riddles all appear on the map.
Make sure you batarang any teeth when you hear the chattering, also interview tapes are classed as riddles
Here is a guide if you are struggling with any riddles.http://www.gamesradar.com/batman-arkham-asylum-riddler-guide...