Sound card
An expansion card providing computer audio input and output.
A sound card, sometimes called an audio card, is a piece of internal hardware that plugs into a computer’s expansion slot, letting software send and receive audio signals. The name also covers external audio interfaces built for professional work. Sound-handling parts can be built directly into the motherboard, using the same kind of components found on add-in cards, and this integrated system is still commonly called a sound card. Modern video cards also include sound processing hardware, using HDMI to carry audio alongside video; earlier models relied on a S/PDIF link to the motherboard or a separate sound card.
Typical jobs for a sound card include handling audio for multimedia tasks like music creation, video or audio editing, presentations, education, games, and video projection. It also supports computer-based communication, such as voice over IP and teleconferencing.
**General characteristics**
Sound cards rely on a digital-to-analog converter (DAC) to turn recorded or generated digital signals into analog form. That output goes to an amplifier, headphones, or an external device through standard connectors like a TRS phone jack. Some cards include a dedicated headphone amplifier for analog headphone output. A common external input is the microphone connector, which feeds signals to speech recognition or voice over IP software. Most cards also have a line-in connector for analog sources with higher voltage than a microphone. In both cases, an analog-to-digital converter (ADC) digitizes the incoming signal. Certain cards contain a sound chip that produces synthesized sounds in real time, generating music and effects with minimal data and CPU usage. The card can use direct memory access to move audio samples between main memory and the card, letting recording and playback software store, edit, or process the data on the hard disk.
**Sound channels and polyphony**
A key trait of a sound card is polyphony—its ability to handle and output multiple independent voices or sounds at once. These distinct channels correspond to the number of audio outputs, which match speaker setups like 2.0 (stereo), 2.1 (stereo plus subwoofer), 5.1 (surround), and others. Sometimes the terms “voice” and “channel” are used interchangeably to describe polyphony, not the speaker configuration.
- Polyphony early chips
- 3 voices, 1 mono output
- Adlib polyphony
- 9 voices, 1 mono output
- Adlib modes
- 9-voice fully programmable mode and percussion mode with 3 regular voices plus 5 percussion voices (total 11)
- Creative music system voices
- 12 voices
- Game blaster retail price
- under $100
- Roland card price range
- hundreds of dollars
Lore & Background
Sound cards for IBM PC–compatible computers were very uncommon until 1988. For the majority of IBM PC users, the internal PC speaker was the only way for early PC software to produce sound and music, typically limited to square waves described as 'beeps and boops'. Several companies developed techniques for digital sound reproduction over the PC speaker, such as RealSound by Access Software, but the resulting audio suffered from distorted output and low volume, and usually required all other processing to stop while sounds played. Other home computers of the 1980s, like the Commodore 64, included hardware support for digital sound playback or music synthesis, leaving the IBM PC at a disadvantage for multimedia applications.
In 1988, a panel of computer-game CEOs stated at the Consumer Electronics Show that the PC's limited sound capability prevented it from becoming the leading home computer, and that it needed a $49–79 sound card with better capability. Sierra On-Line promised that year to support the AdLib, IBM Music Feature, and Roland MT-32 sound cards in its games. A 1989 Computer Gaming World survey found that 18 of 25 game companies planned to support AdLib, six Roland and Covox, and seven Creative Music System/Game Blaster.
One of the first manufacturers of sound cards for the IBM PC was AdLib, which produced a card based on the Yamaha YM3812 sound chip (OPL2). Creative Labs marketed the Creative Music System (C/MS) at about the same time, which had twelve voices to AdLib's nine and was stereo, but its technology was based on a square-wave generator and failed to sell well. Creative later introduced the Sound Blaster, which cloned the AdLib and added a sound coprocessor for recording and playback of digital audio, a game port, and MIDI capability. It eventually outsold the AdLib and dominated the market. Roland also made sound cards such as the MT-32 and LAPC-I, selling for hundreds of dollars, and many games had music written for them.
Reader's Guide
The sound card's significance lies in its role as the primary means for IBM PC-compatible computers to produce and capture audio, enabling multimedia applications such as music composition, video editing, education, entertainment (games), and computer-based communication like voice over IP and teleconferencing. Before widespread adoption, the PC speaker limited audio to simple square waves, putting the platform at a disadvantage compared to home computers like the Commodore 64. The 1988 Consumer Electronics Show panel of game company CEOs highlighted this gap, calling for a $49–79 sound card to unlock the PC's multimedia potential. AdLib's card, based on the Yamaha YM3812 chip, became an early standard, but Creative Labs' Sound Blaster—which cloned AdLib and added digital audio recording and playback—dominated the market after being recommended by Microsoft for the Multimedia PC standard. Roland's higher-priced cards offered superior music quality but were poor at sound effects. The legacy of these early cards is seen in modern integrated sound on motherboards and video cards, which continue to provide audio functionality. The article notes that many modern low-cost integrated sound cards lack hardware polyphony, performing tasks in software, similar to softmodems. Sound cards also introduced color-coded connectors per the PC System Design Guide, a standard still used on many desktop PCs.
Did You Know?
- The AdLib sound card had two modes: a 9-voice fully programmable mode and a percussion mode with 3 regular voices plus 5 percussion voices for a total of 11.
- Roland sound cards such as the MT-32 and LAPC-I sold for hundreds of dollars and were considered the best for music until the mid-nineties, but were often poor at sound effects.
- Modern low-cost integrated sound cards often have no actual hardware polyphony for sound effects or MIDI reproduction, performing these tasks entirely in software.
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