Here is an interesting comparison of Cortana over the course of the 4 halo games:
PTesh adds his dulcet prepubescent tones over the top of one of the new trailers for weapons...
Try upgrading your browser to Google chrome (you wont regret it). There is probably an IE...
Level: Truth and Reconciliation
Make your way to the 3rd battle area, the one right before the grav lift part, clean up all the enemies and move on just a little bit to the next are to make the music stop, then go back to the empty area. Then stand near any of these spots, and you should hear various sounds of distant animals. (do NOT stand at the area from the shot is taken, stand where the crosshairs are pointing to. Also in the 1st picture, stand below that tree. In the 2nd picture, stand anywhere around that tree).