Announcer

The Announcer plays a small part in Portal 2. He guides the player with pre-recorded messages through the facility early on in the game.

The Announcer is most likely an automated system created to monitor the Aperture lab complex prior to the activation of GLaDOS, and lately left as a backup system to keep research and testing going even during "circumstances of potentially apocalyptic significance". Designed to work in extreme and low power conditions, the system seems to have been automatically turned on However, the Announcer appears to maintain control of certain ancillary functions,  He is voiced by Joe Michaels.