Mic voice in world
I have an idea not sure if it would work, is have a mic on the oculus rift so u can here ur own voice in the game but depending where u are in the game u would here ur voice different so if ur in a cave it would have an echo the game could even realitically bounce ur voice of walls, or if your underwater ur voice would change to what it would sound like, maybe in a scary game u might here samples of ur voice used in some creepy way, not sure if this could work inless u use noise cancelling headphones so you cant hear you own voice but if it did i think it would add somthing to the being there effect.
