|Wednesday, 25 October 2006|
Computer systems provide stereo sound capability by utilizing a sound card for controlling audio devices (for example, two speakers in conjunction with suitable amplifiers), an audio device driver (also called a sound driver) for controlling the sound card, and an operating system which supports stereo sound, for interacting with both the device driver and stereo application programs. The sound card receives and digitizes the analog signals generated by the input device. The digital signals are processed by the processor, such as a digital signal processor (DSP), of the computer for performing functions such as storage of the audio file in memory or other audio related functions. The digital signal processor can perform frequency modulation synthesis for the various functions of the sound board. The DSP typically performs signal processing used for a variety of multimedia applications, such as electronic data processing, high precision servo control, graphics various capabilities for work stations, robotics, image processing, process control, real time simulation and instrumentation, speech recognition and synthesis, and telecommunication capabilities such as PBX, modems and faxes. Sound cards have a coder/decoder or analog-to-digital and digital-to-analog conversion capability. Such a capability allows translation between the digital signals utilized by the computer and analog input or output audio signals. Computer users can thus record and enhance analog audio signals by utilizing the music application software to further process the digitized audio signals or by mixing in other digital or digitized signals. A sound card is an audio processing circuitry mounted on a printed circuit board that plugs into the computer. This enables programs to generate sounds and synthesized speech which are sent to speakers connected to the sound card. Many sound cards also have an input for a microphone which picks-up the user's voice for digitizing by the audio processing circuitry. Sound cards of this type are used for bidirectional audio communication over the Internet. Several connectors may be part of a sound card to provide digital or analog connections thereto. Such connectors include one or more microphone in connectors, line in and line out connectors, loudspeaker out connectors, musical instrument digital interface (midi) ports, joystick port, optical or coaxial digital I/O card connectors, and headphone outs connectors.
Audio output from the sound card is generally of high quality (broad frequency response range, low distortion and high output). Multimedia computers, having multiple audio and video functions and using built-in sound cards and video cards, are widely distributed, such that a personal computer can now be readily used in place of a home entertainment center. Sound cards may produce or enhance a sound representing a prompt or other sound from an ordinary computer program, sounds for video games played on the computer, and downloadable music or sounds such as, for example, in an MPEG Audio Layer standard. In digital audio, quantization and sampling processes are used to generate the data representing the amplitude (level) element of sound and the frequency (events over time) element of sound. The sound card converts digitally encoded audio to analog sound signals capable of driving the computers loudspeakers. In addition to an interface with the computer bus, sound cards typically provide an interface to a player that is capable of playing music and/or video, such as compact discs and digital video disk. They also support proprietary interfaces for the CD-ROM player, as well as standard interfaces such as SCSI and IDE/EIDE standards. A sound card may process signals from CD-ROMS or other play-back equipment, downloaded or stored files, musical instruments, and the like. Different sound boards have different components, but generally they add the ability to produce sound which can be used for prompts or otherwise in ordinary computer programs, or as sound for video games played on a computer. Multiple sound cards can also be inserted into a computer system so that it would be possible to simultaneously connect multiple audio transducers. Application software could allow a user to switch between the different sound cards.