Sound

Sound is never noticed by users, until it isn't there. It forms an integral part of the user feedback experience. For example, the beeps produced by Windows Explorer, KDE and other desktop environments when users click on the wrong thing. It is also becoming a far more dominant part of the gaming and multimedia experience; with many games and movies now featuring 5.1 channel soundtracks. As such, it is becoming more important for hobby operating systems to support sound playback, at the very least.

A Short History of PC Sound

The original sound device on PCs was the PC Speaker, available as far back as the IBM PC (introduced in 1981). In the late 1980s several manufacturers started producing add-in sound devices, notably Creative (the Game Blaster) and AdLib (the AdLib Music Synthesizer Card). Of these, Creative was far more successful, and the Sound Blaster 16 became a de-facto standard for more than half a decade. Almost all cards today still have some backwards compatibility with the Sound Blaster 16.

In 1997 Intel specificed a new standard, AC97 (short for Audio Codec 1997), that virtually replaced the Sound Blaster standard by specifying higher quality sampling. In 2004 Intel produced yet another standard, this time the Intel High Definition Audio standard (codenamed Azalia), which specifies yet another improvement on previous standards' audio quality.

Sound cards and standards for the professional (and audiophile) markets have evolved seperately from the mainstream cards. The important feature in these cards is not fancy features, but very low latency (<5ms) and high quality sampling (24 bit sampling at 96KHz not being uncommon). MIDI is an important part of professional audio today, and has been since the early 1990s. Cards can be from 2 channels through to 32 and more.

The Sound Heirachy

• In Progress
• Stubs
• Sound