Unidentified interviewer
From Halopedia, the Halo wiki
Unidentified interviewer is an unseen character (the viewer only hears his voice) in the Believe trailers for Halo 3. Although he is not seen, he sounds like a middle-aged man with an English accent. He interviews some retired soldiers about their experiences during the Human-Covenant War for the Museum of Humanity, therefore it is quite likely he works there, however, he is also seen out in the woods in one of the shorts.
