This trophy is obtained after completing the optional quest The Secret Chamber
which you obtain from Pickle.
Its not a difficult one by any means, but I did have a hard time retrieving 2 of the recorders because I forgot you can sometimes shoot the power boxes beside the jump pads to make them throw you significantly farther.
-Simply head to the location in the ship and try to open the door.
-You will have to retrieve 3 voice recorders in order to open the door.
-Shoot the electric box beside the jump pad within the same area you are currently in and jump way up to the top of the room.
-Shoot the lock on the elevator door to get inside and get your first ECHO.
-Run, jump and boost to get across the large gap to get the second ECHO.
-The final ECHO is outside this room, downstairs. A large door will open and several enemies will come out. Kill them and the ECHO will drop from them.
-At this point you can open the door, get your trophy and receive Zarpedon's pistol as well as some other loot.