Even if you have an antique PC that lacks sound circuitry, it can still make noise: Just toss it through a window! (Sadly, this noise-making trick works only once for each PC and window.)

All PCs now have either built-in sound smarts or sound expansion cards that let them do more than just BEEP the internal speakers.

The hardware that brings on da noise

Your PC comes with sound circuitry either included directly on the motherboard or on an expansion card plugged into an expansion slot (also on the motherboard). That sound circuitry can do some amazing things.

The first thing the sound circuitry does is to play wave sounds, which are the recorded sounds you hear when you turn on your computer or run a program. They're also the sounds you hear when you play a computer game: a ding-dong for a correct answer, your opponent saying "ouch," or the sound of spent shotgun shells hitting a concrete floor. They're all wave sounds.

The second thing the sound circuitry does is to play music on a built-in synthesizer. Special music files, known as MIDI files, direct the synthesizer to play all sorts of songs, from classical music to sitcom themes. Depending on the sophistication of the sound circuitry, the synthesizer can produce quite realistic-sounding music.

Third, the sound circuitry helps amplify and play music from your computer's CD-ROM drive.

Finally, you can use the sound circuitry to record and play back your own sound files.