Sound cards are computer expansion cards that enable audio inputs and outputs. They connect to the computer via the internal bus or an external connection. Sound cards provide an audio input, an audio output, or both. Some devices provide multiple inputs or outputs. Others use digital signals and optical connectors to provide surround sound, a technology used in many cinemas and home theater systems.
Sound cards are also used in gaming systems, multimedia applications, and for both audio and video editing. Specialty products are available for phone messaging systems and public address (PA) systems. High-end or professional-grade sound cards are used for studio recording, audio analysis, and other professional audio applications.
Sound cards are essentially special-purpose digital-to-analog converters (DACs) and/or analog-to-digital converters (ADCs) for use with audio. Most sound cards include one or more DACs, computer chips that convert digital signals that represent binary numbers into proportional analog voltages. These sound cards may also include ADCs that sample an analog signal and convert it to a series of digital values to represent the signal to a computer processor. Through standard interconnects, the signal is connected to a devices such as an amplifier or headphones. Other inputs and outputs include optical and coaxial.
In addition to professional and gaming, designations for sound cards include 5.1 and 7.1. Sound cards may include digital signal processors (DSPs), surround sound capabilities, digital inputs and outputs, a musical instrument digital interface (MIDI), and gold-plated contacts. Some advanced sound cards feature multiple sound chips to provide higher data rates. Digital sound reproduction may require multi-channel DACs to apply real-time effects such as filtering and distortion. Sound cards with a line-in connector for signals from an external device such as microphone are also available. These sound cards digitize the signal and store the data on the computer hard disk (HDD) for subsequent storage, retrieval, and processing.
Communication Protocols and Standards
Typically, sound cards use common communications protocols or standards such as peripheral component interconnect (PCI), PCI Express (PCIe), IEEE 1394 or FireWire (Apple Computer, Inc.), or universal serial bus (USD). PCMCIA sound cards are also available. An acronym for Personal Computer Memory Card International Association, PCMCIA is a standard that was designed originally for adding memory to portable computers. Sound cards that use other protocols and standards are also available.