Frequent radio transmissions through the player’s communications device also add to the atmosphere, by broadcasting certain sounds and messages from non-player characters meant to unsettle the player. Early in the game, during and directly after the event that plunges the base into chaos, the player often hears the sounds of fighting, screaming and dying through their radio transmitter. The ambient sound is extended to the base itself through such things as hissing pipes, footsteps, and occasional jarringly loud noises from machinery or other sources. Often ambient sounds can be heard that resemble deep breathing, unexplained voices and demonic taunting from the game’s antagonists.

Early in the game, the player is provided with a personal data assistant (PDA). PDAs contain security clearance levels, allowing the player to access certain areas that are otherwise locked and off-limits. Additionally, the PDA can be used to read e-mails and play videos that the player’s character acquires during the game. Whenever the player picks up any of the other PDAs found throughout the game, its contents are automatically downloaded to the player’s own device. Other PDAs often contain e-mails and audio logs for other characters, which can provide useful information such as storage or door key codes, as well as significant plot details.

Doom 3 was released with a four-player multiplayer element, featuring four game modes. However, the game’s community created a modification to boost this to eight or sixteen players. The Resurrection of Evil expansion would later officially increase the player limit to eight. The four game modes are all deathmatches. The standard deathmatch game mode involves each player moving around a level, collecting weaponry and killing the other players, with the player with the highest kills when the time runs out winning. A team variation of this involves the same principle.

The third game mode is “last man standing”, in which each player has a limited amount of respawns, with players losing a life when they are killed. Eventually, all but one player will be eliminated from the game, leaving the survivor as the winner. The final game mode is “tournament”, in which two players fight each other while the other players watch as spectators. The victor of the battle remains in the arena, facing each other player one at a time until the winner of previous rounds is defeated. The loser then moves to the spectators and the new winner remains to fight the next player. The Xbox version of Doom 3 also incorporates an additional two-