Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing... A typical sound card includes a sound chip, usually fe
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Sound card
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A Sound Blaster Live! Value card, a typical present-day PCI sound card
A sound card is a computer expansion card that can input and output sound under
control of computer programs Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing
Trang 2video or audio, presentation/education, and entertainment (games) Many
computers have sound capabilities built in, while others require these expansion cards if audio capability is desired
Contents
[hide] [hide]
1 General characteristics
o 1.1 Connections
o 1.2 Voices vs channels
2 History of sound cards for the IBM PC architecture
o 2.1 Hardware manufacturers
o 2.2 Industry adoption
o 2.3 Feature evolution
3 Sound devices other than expansion cards
o 3.1 Integrated sound on the PC
o 3.2 Integrated sound on other platforms
o 3.3 USB sound cards
o 3.4 Other outboard sound devices
4 Driver architecture
5 See also
6 References
7 External links
[edit]
General characteristics
Close-up of a sound card PCB, showing electrolytic capacitors (most likely for AC coupling), SMT capacitors and resistors, and a YAC512 two-channel 16-bit DAC
Trang 3A typical sound card includes a sound chip, usually featuring a digital-to-analog converter, that converts recorded or generated digital waveforms of sound into an analog format This signal is led to a (typically 1/8-inch earphone-type) connector where an amplifier, headphones, or similar sound destination can be plugged in More advanced designs usually include more than one sound chip to separate duties between digital sound production and synthesized sounds (usually for real-time generation of music and sound effects utilizing little data and CPU real-time)
Digital sound reproduction is usually achieved by multi-channel DACs, able to play multiple digital samples at different pitches and volumes, optionally applying real-time effects like filtering or distortion Multi-channel digital sound playback can also be used for music synthesis if used with a digitized instrument bank of some sort, typically a small amount of ROM or Flash memory containing samples corresponding to the standard MIDI instruments (A contrasting way to synthesize sound on a PC uses "audio codecs", which rely heavily on software for music synthesis, MIDI compliance and even multiple-channel emulation This approach has become common as manufacturers seek to simplify the design and the cost of the sound card itself)
Most sound cards have a line in connector where the sound signal from a cassette
tape recorder or similar sound source can be input The sound card can digitize this signal and store it (controlled by the corresponding computer software) on the computer's hard disk for editing or further reproduction Another typical external
connector is the microphone connector, for connecting to a microphone or other input device that generates a relatively lower voltage than the line in connector
Input through a microphone jack is typically used by speech recognition software
or Voice over IP applications
[edit]
Connections
Most sound cards since 1999 conform to Microsoft's PC 99 standard for color coding the external connectors as follows:
Pink Analog microphone input
Trang 4Light blue Analog line level input
Lime
green
Analog line level output for the main stereo signal (front speakers or headphones)
Black Analog line level output for rear speakers
Orange S/PDIF digital output (sometimes used as an analog line output for a
center speaker instead) [edit]
Voices vs channels
Another important characteristic of any sound card is the number of distinct voices
(intended as the number of sounds that can be played back simultaneously and independently) and the number of channels (intended as the number of distinct electrical audio outputs)
For example, many older sound chips had three voices, but only one audio channel (mono) where all the voices were mixed into, while the AdLib sound card had 9 voice and 1 mono channel
For a number of years, most PC sound cards had multiple FM synthesis voices (typically 9 or 18) which were mostly used for MIDI music, but only one (mono)
or two(stereo) voice(s) and channel(s) dedicated to playing back digital sound samples, and playing back more than one digital sound sample required performing
a software downmix at a fixed sampling rate Modern low-cost integrated
soundcards using an audio codec like the AC'97 still work that way, although they may have more than two sound output channels (surround sound)
Today, a sound card having hardware support for more than the two standard
stereo voices, is likely to referred at as "providing hardware audio acceleration"
[edit]
History of sound cards for the IBM PC architecture
Trang 5A sound card based on VIA Envy chip
Echo Digital Audio Corporation's Indigo IO — PCMCIA card 24-bit 96 kHz stereo in/out sound card
Sound cards for computers based on the IBM PC were uncommon until 1988, leaving the internal PC speaker as the only way early PC software could produce sound and music The speaker was limited to square wave production, leading to the common nickname of "beeper" and the resulting sound described as "beeps and boops" Several companies, most notably Access Software, developed techniques for digital sound reproduction over the PC speaker; the resulting audio, while
functional, suffered from distorted output and low volume, and usually required all other processing to halt while sounds were played Other home computer models
of the 1980s included hardware support for digital sound playback or music
synthesis (or both), leaving the IBM PC at a disadvantage when it came to
multimedia applications such as music composition or gaming
It is important to note that the initial design and marketing focuses of sound cards
for the IBM PC platform were not based on gaming, but rather 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) It took the involvement of
Sierra and other game companies in 1988 to switch the focus toward gaming
[edit]