A sound card is a plug-in card for a personal computer, which converts electrical signals into sound. If it is in its own housing, we speak again of an audio interface. Depending on the nature and performance of the sound card can be reproduced by simple tones to the music in studio quality everything. The scope of sounds is measured in voices. Music in studio-quality example, consists of 128 voices.
Nowadays, the sound card is connected to the motherboard internally via the PCI or PCI Express bus, that processed the analog and digital audio signals. External sound cards can also be connected via a USB port, a PCMCIA or ExpressCard slot to the motherboard. In the professional field, FireWire connections are increasingly being used. Older sound cards have an ISA bus.
The sound card behaves himself as a motherboard and has its own mini-CPU and a memory. Since the 2000s there has been a change in computer technology, which led to the sound cards are becoming less manufactured as plug-in cards, but as a microchip directly on the motherboard are integrated.
The tasks of the sound card is, the recording, synthesis, mixing, editing and playback of audio signals. Analog audio signals are digitized by the AD converter and then stored in a specified storage format, .wav or .mp3 for example, on the memory (RAM). From there, the digitized files are loaded on the hard drive and converted into analog sounds that are finally output by the speakers. The quality of the audio output differs from the quantization/bit resolution, so the signal processing (8 bits, 16 bits or 24 bits) and the maximum sampling rate (22, 44, 96 or 128 kHz) from, as well as the noise performance, the frequency response and the computer internal shielding against interference.
The sound card has various inputs and outputs, were the sounds are recorded or output. These exist in different versions: analog, digital and Gameport/MIDI (Musical Instrument Digital Interface). The analog inputs/outputs include the input of the microphone (pink), the line-in for AUX/external sources (blue), the line-out/output for headphone or (front) speaker (green), the output for rear speakers (black), the output for side speakers (white) and the output for center and subbass speaker (orange).
Some sound cards also have a S/DPIF port via which the synchronization with another sound card is possible. In addition, many sound cards support the various sound output standards like EAX, DTS-ES or ASIO. Modern and cost intensive sound cards also feature an accelerator chip that relieve the processor (CPU) to computational load. Depending on what the sound card is to be used, it is important to distinguish between a consumer hardware and a professional sound card.
The consumer hardware mainly include Nvidia, Gravis, Realtek, Asus, Aztech, AdLib, Creative Labs, Philips and TerraTec as leading manufacturers of sound cards. In the professional field particularly Akai, Avid/Digidesign, Roland and Native Instruments as well as Steinberg, Universial Audio and Yamaha are mentioned.