A sound card also known as “audio card” or “audio adapter” is a peripheral device of a computer which handles the functions related to sound. The sound card is attached either to an ISA (Industry Standard Architecture) or PCA (Peripheral Component Interconnect) slot on the motherboard of the computer. The sound card receives input sound from an input device (e.g. Microphone), records the sound and performs some manipulations and delivers the resulting sound as output. It basically functions as digital-to-analog converter which converts the input digital signal to an analog format. The output devices include amplifiers, headphones or some external devices using standard interconnects (e.g. TRS connector, RCA connector). The sound cards are commonly used in multimedia applications like music composition, editing video or audio, presentation/education, and entertainment (games).
The major functions of sound cards are:
a] Synthesis (sound generation from digital signals)
b] MIDI (Musical Instrument Digital Interface: a standard protocol which allows electronic devices communicate, control and synchronize each other. Simply we can say that MIDI allows exchange of system data)
c] Analog-to-Digital converter (e.g. converts the input analog sound signals from microphone to digital mode)
d] Digital-to-Analog converter (e.g. reconverts the digital signals to output analog signals)
The sound synthesis includes three methods. They are FM (Frequency Modulation) synthesis, Wavetable synthesis and Physical Modeling.
Before the invention of sound cards it was widely believed that computers are not designed to produce sound or music. The computers then, had an internal PC Speaker which could deliver only a beep sound, which was produced occasionally as alarm or warning. Eventually, computer programmers thought of giving beep as accompaniment for the games. Even then they could produce only beep sound for the game. Initially the sound cards was designed and marketed for IBM PC , based on specific audio applications such as music composition (AdLib Personal Music System, Creative Music System, IBM Music Feature Card) or on speech synthesis (Digispeech DS201, Covox Speech Thing, Street Electronics Echo).By 1988 game companies such as Sierra started switching towards adding sound effects in games.
In the beginning, sound cards for IBM PC were manufactured by AdLib. The card was based on Yamaha YM3812 sound chip, aka the OPL2.At the same time; Creative Labs also marketed a sound card called the Creative Music System. The Creative Labs introduced the Sound Blaster card which created a major twist in the IBM PC compatible sound card market. The Sound Blaster had an additional processor for recording and play back of digital audio in addition to the AdLib model.
As of now, in the commercial market, sound cards are available in a price range of $10 to costly models of $1000.