| A sound card is a computer expansion card | | | | played back simultaneously and independently) |
| that can input and output sound under control | | | | and the number of channels (intended as the |
| of computer programs. Typical uses of sound | | | | number of distinct electrical audio outputs). |
| cards include providing the audio component | | | | |
| for multimedia applications such as music | | | | For example, many older sound chips had three |
| composition, editing video or audio, | | | | voices, but only one audio channel (mono) |
| presentation/education, and entertainment | | | | where all the voices were mixed into, while |
| (games). Many computers have sound | | | | the AdLib sound card had 9 voice and 1 mono |
| capabilities built in, while others require | | | | channel. |
| these expansion cards if audio capability is | | | | |
| desired. | | | | For a number of years, most PC sound cards |
| | | | had multiple FM synthesis voices (typically 9 |
| A typical sound card includes a sound chip, | | | | or 18) which were mostly used for MIDI music, |
| usually featuring a digital-to-analog | | | | but only one (mono) or two(stereo) voice(s) |
| converter, that converts recorded or | | | | and channel(s) dedicated to playing back |
| generated digital waveforms of sound into an | | | | digital sound samples, and playing back more |
| analog format. This signal is led to a | | | | than one digital sound sample required |
| (typically 1/8-inch earphone-type) connector | | | | performing a software downmix at a fixed |
| where an amplifier, headphones, or similar | | | | sampling rate. Modern low-cost integrated |
| sound destination can be plugged in. More | | | | soundcards using an audio codec like the |
| advanced designs usually include more than | | | | AC'97 still work that way, although they may |
| one sound chip to separate duties between | | | | have more than two sound output channels |
| digital sound production and synthesized | | | | (surround sound). |
| sounds (usually for real-time generation of | | | | |
| music and sound effects utilizing little data | | | | Today, a sound card having hardware support |
| and CPU time). | | | | for more than the two standard stereo voices, |
| | | | is likely to referred at as "providing |
| Digital sound reproduction is usually | | | | hardware audio acceleration". |
| achieved by multi-channel DACs, able to play | | | | |
| multiple digital samples at different pitches | | | | In 1984, the IBM PCjr debuted with a |
| and volumes, optionally applying real-time | | | | rudimentary 3-voice sound synthesis chip, the |
| effects like filtering or distortion. | | | | SN76489, capable of generating three |
| Multi-channel digital sound playback can also | | | | square-wave tones with variable amplitude, |
| be used for music synthesis if used with a | | | | and a pseudo white noise channel that could |
| digitized instrument bank of some sort, | | | | generate primitive percussion sounds. The |
| typically a small amount of ROM or Flash | | | | Tandy 1000, initially being a clone of the |
| memory containing samples corresponding to | | | | PCjr, duplicated this functionality, with the |
| the standard MIDI instruments. (A contrasting | | | | Tandy TL/SL/RL line adding digital sound |
| way to synthesize sound on a PC uses "audio | | | | recording/playback capabilities. |
| codecs", which rely heavily on software for | | | | |
| music synthesis, MIDI compliance and even | | | | In the late 1990s, many computer |
| multiple-channel emulation. This approach has | | | | manufacturers began to replace plug-in |
| become common as manufacturers seek to | | | | soundcards with a "codec" (actually a |
| simplify the design and the cost of the sound | | | | combined audio AD/DA-converter) integrated |
| card itself). | | | | into the motherboard. Many of these used |
| | | | Intel's AC97 specification. Others used cheap |
| Most sound cards have a line in connector | | | | ACR slots. |
| where the sound signal from a cassette tape | | | | |
| recorder or similar sound source can be | | | | As of 2005, these "codecs" usually lack the |
| input. The sound card can digitize this | | | | hardware for direct music synthesis or even |
| signal and store it (controlled by the | | | | multi-channel sound, with special drivers and |
| corresponding computer software) on the | | | | software making up for these lacks, at the |
| computer's hard disk for editing or further | | | | expense of CPU speed (for example, MIDI |
| reproduction. Another typical external | | | | reproduction takes away 10-15% CPU time on an |
| connector is the microphone connector, for | | | | Athlon XP 1600+ CPU). |
| connecting to a microphone or other input | | | | |
| device that generates a relatively lower | | | | Nevertheless, some manufacturers offered (and |
| voltage than the line in connector. Input | | | | offer, as of 2006) motherboards with |
| through a microphone jack is typically used | | | | integrated "real" (non-codec) soundcards |
| by speech recognition software or Voice over | | | | usually in the form of a custom chipset |
| IP applications. | | | | providing e.g. full ISA or PCI Soundblaster |
| | | | compatibility, thus saving an expansion slot |
| Another important characteristic of any sound | | | | while providing the user with a (relatively) |
| card is the number of distinct voices | | | | high quality soundcard. |
| (intended as the number of sounds that can be | | | | |