Audio is the sound system that comes with or can be added to a computer. An audio card contains a special built-in processor and memory for processing audio files and sending them to speakers in the computer. An audio file is a record of captured sound that can be played back. Sound reinforcement system, a system for amplifying audio for an audience. High fidelity, a sound system intended for accurate reproduction of music in the home. Public address, an institutional speech-reinforcement or public safety announcement system. Shelf stereo, a compact sound systemfor personal use.