The game is recorded on an iRiver 800. It has 256MB storage capacity. When set to record in stereo at 44 kHz at 128 kbps, that's enough for about 4 hours 30 minutes of recording. A Sony stereo microphone (ECM-DS30P) is plugged into the line-in port.
The MP3 file is copied to my Mac, then loaded into Audacity. I apply the Noise Reduction filter (using a sample of the ambient room noise), then 6:1 compression, then either 6 or 12dB (sometimes 15dB when the recorder battery was low) of amplification. The file is then exported as an MP3 file at 64kb bitrate (80 kbps for Masks, there were some bad artifacts in the introductory audio when I exported at 64). Recently I have not needed to apply noise reduction because the room fan hasn't been constantly running.
The Masks of Nyarlathotep, Day of the Beast, and The Haunting voice-overs were put together using GarageBand with me recording the main audio track. The intro to Adventure! Serial 1 was pieced together from snippets of the pre-adventure hooks which were recorded and edited with Audacity, then placed into GarageBand. The final audio was then sent to iTunes. All of the sound effects and music were from GarageBand.