References and easter eggs you found

[Kurton]

When you first enter the diving room at Omicron (before Catherine turns on the lights) you can hear a faint whispering - same one you hear when you use a save-artifact in Penumbra

In the music files there is also a 00_00_ringtone.ogg that's a snippet from the Overture credits music, but I don't remember hearing it in-game