Sound

The sounds in Doom and Doom II were compiled by Bobby Prince, and in Heretic and Hexen compiled by Kevin Schilder. Many of Doom's sounds are from Sound Ideas' General series sound effects library.

The sound support for the Doom engine was programmed by Paul Radek. Because Id Software did not own this sound library, the original DOS source code could not be distributed freely, and the sound system had to be removed first..

Sound lumps in the WAD file are stored in the DMX format; which consists of a short header followed by raw 8-bit, monaural unsigned data, typically at a sampling rate of 11025 Hz, although some sounds use 22050 Hz. Each sample is one byte (8 bits).

The Doom engine also provides for PC speaker sound effects, which consist of various tones played through the PC speaker. Other than playing without sound, this was the only option for those who did not own a sound card when the game was released. The sound effect format for PC speaker sound is roughly similar, but does not contain the sample rate; instead a constant sample rate of 140 Hz is assumed. A sample has a value between 0 and 95 inclusive. 0 corresponds to silence; 1 is the note F-3 (175 Hz), and 95 is the note E-7 (2640 Hz). There is one value per quartertone. A more precise table of each sample value's note and frequency can be found in the format description written by Simon Howard and Andrew Apted.

Source

 * Unofficial Doom Specs