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Sound Card's functions

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Old 27-02-2009
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Sound Card's functions
  

A sound card or audio board which allows computers to output audio signals through speakers and/or headphones. Originally, when computers were first released, it produced no more than various tones generated through the PC Speaker.

A sound card (also known as an audio card) is a computer expansion card that facilitates the input and output of audio signals to/from a computer under control of computer programs. Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation/education, and entertainment (games). Many computers have sound capabilities built in, while others require additional expansion cards to provide for audio capability.


Sound cards usually feature a digital-to-analog converter, that converts recorded or generated digital data into an analog format. The output signal is connected to an amplifier, headphones, or external device using standard interconnects, such as a TRS connector or an RCA connector. If the number and size of connectors is too large for the space on the backplate the connectors will be off-board, typically using a breakout box, or an auxiliary backplate. More advanced cards usually include more than one sound chip to provide for higher data rates and multiple simultaneous functionality.

Most sound cards have a line in connector for signal from a cassette tape recorder or similar sound source. The sound card digitizes this signal and stores it (under control of appropriate matching computer software) on the computer's hard disk for storage, editing, or further processing. Another common external connector is the microphone connector, for use by a microphone or other low level input device. Input through a microphone jack can then be used by speech recognition software or for Voice over IP applications.

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Old 27-02-2009
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smile Re: Sound Card's functions

Before the invention of the sound card, a PC could make one sound - a beep. Although the computer could change the beep's frequency and duration, it couldn't change the volume or create other sounds.

At first, the beep acted primarily as a signal or a warning. Later, developers created music for the earliest PC games using beeps of different pitches and lengths. This music was not particularly realistic -- you can hear samples from some of these soundtracks at Crossfire Designs.


Fortunately, computers' sound capabilities increased greatly in the 1980s, when several manufacturers introduced add-on cards dedicated to controlling sound. Now, a computer with a sound card can do far more than just beep. It can produce 3-D audio for games or surround sound playback for DVDs. It can also capture and record sound from external sources.

Sound cards for computers compatible with the IBM PC were very uncommon until 1988, which left the single internal PC speaker as the only way early PC software could produce sound and music. The speaker hardware was typically limited to square waves, which fit the common nickname of "beeper". The resulting sound was generally 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 baldly functional, suffered from distorted output and low volume, and usually required all other processing to be stopped 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 to them when it came to multimedia applications such as music composition or gaming.

Generally, there will be a total of four connections: MIDI / Game port is a port which is most commonly used for the game port which will allow you to connect a game paddle (Joypad) and/or Joystick to the computer. This port will also allow you to connect a device such as a MIDI keyboard to the computer; additional information on this can be found in the Midi section.

Line In connector allows you to connect a Cassette Tape, CD or record player to the computer.

Line Out connector is the location which the speakers or headphones will be connected to get sound out of the sound card.

Volume control is generally no longer found on sound cards. However, for cards that do include this as a feature, this allows for the volume to be turned up and down on a non amplified output such as a set of headphones.

Microphone allows you to connect a microphone to the computer and record your own sound files.

Today you will find several manufacturers whom are beginning to identify each of the above ports by symbols on the back of the sound card
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Old 27-02-2009
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Re: Sound Card's functions

A sound card (also known as an audio card) is a computer expansion card that facilitates the input and output of audio signals to/from a computer under control of computer programs. Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation/education, and entertainment.

Originally, when computers were first released, it produced no more than various tones generated through the PC Speaker. Because of the importance of audio, several manufacturers, such as Adlib, Roland and Creative Labs, released several types of audio boards during 1984 to 1989. Unfortunately, still today there has been no official standard for PC audio adapters. During the years, the Sound Blaster cards by Creative Labs have emerged as the de facto standard. Because of this, most cards and software applications will be marked as Sound Blaster compatible.

Sound cards have several uses and has become a standard option which comes with computers today. Below is a listing of some of the various functions of the sound card:

Audio CDs.
Audio conferencing.
Business presentations.
Creating and playing Midi.
Educational software.
Games.
Record dictations.
Voice recognition
Watch movies.

MIDI

MIDI, or Musical Instrument Digital Interface, developed in the 1980s, allows various musical instruments to communicate or play harmoniously. MIDI is a limited method of playing sounds as it will only be capable of playing the instruments available to your sound card. This is why MIDI files may sound better or worse on different computers.

Generally, most computer sound cards will have a MIDI port which allows for several musical instrument devices to be connected to the computer such as a MIDI keyboard or a synthesizer. Before connecting any of these devices to the computer, you will need to purchase a separate cable which takes the MIDI/Game port connection into the standard 5-pin DIN midi connector.

MP3

MP3 is a new technology using MPEG compression shrinking down that data by a factor of 12 and still gain CD-like quality. Factors of up to 24 and more still allow for a quality significantly better than just reducing linearly the sampling frequency and the number of bits. This is realized by "perceptual coding" techniques taking into account the limited resolution of the human ear. Maybe you have already heard about MP3. As interest in audio over the Internet increased, MPEG Layer-3 files, music files that are capable of storing long audio tracks with CD quality sound in a fraction of the space, appeared. With this ease of piracy, it's a shock to the entire music industry.



An important characteristic of sound cards is polyphony, which is more than one distinct voice or sound playable simultaneously and independently, and the number of simultaneous channels. These are intended as the number of distinct electrical audio outputs, which may correspond to a speaker configuration such as 2.0 (stereo), 2.1 (stereo and sub woofer), 5.1 etc. Sometimes, the terms "voices" and "channels" are used interchangeably to indicate the degree of polyphony, not the output speaker configuration.

For example, many older sound chips could accommodate three voices, but only one audio channel (ie, a single mono output) for output, requiring all voices to be mixed together. More recent cards, such as the AdLib sound card, have a 9 voice polyphony and 1 mono channel as a combined output.

For some years, most PC sound cards have had multiple FM synthesis voices (typically 9 or 16) which were usually used for MIDI music. The full capabilities of advanced cards aren't often completely used; only one (mono) or two (stereo) voice(s) and channel(s) are usually dedicated to playback of digital sound samples, and playing back more than one digital sound sample usually requires a software downmix at a fixed sampling rate. Modern low-cost integrated soundcards (ie, those built into motherboards) such as audio codecs like those meeting the AC'97 standard and even some budget expansion soundcards still work that way. They may provide more than two sound output channels (typically 5.1 or 7.1 surround sound), but they usually have no actual hardware polyphony for either sound effects or MIDI reproduction, these tasks are performed entirely in software. This is similar to the way inexpensive softmodems perform modem tasks in software rather than in hardware).

Today, a sound card providing actual hardware polyphony, regardless of the number of output channels, is typically referred to as a "hardware audio accelerator", although actual voice polyphony is not the sole (or even a necessary) prerequisite, with other aspects such as hardware acceleration of 3D sound, positional audio and real-time DSP effects being more important.
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