Doom 3 has no sound
The no sound with Doom 3 issue can be resolved by changing the default bit rate in your Midi Setup from 2ch - 24bit to 2ch -16Bit.
To do this, open the Audio Midi Setup control panel in the Applications/Utilities folder.
Change "Properties For": to "Built - in Output" instead of "Built-in Mic". This will show you the Output options. The sample rate should be at 44,100hz, but the Bit rate is defaulted to 2ch - 24bit. Change that to 2ch -16Bit. Once this is changed, Doom 3 should have sound from the internal speaker without having to plug in speakers or headphones.