What is Sound card?
[[File:Sblive!.jpg|thumb|Creative [[Sound Blaster]] [[Live!]], a [[PCI]] sound card]] A '''sound card''' (or '''audio card''') is the part of the [[computer hardware]] that controls the input and output of the sound signals. A sound card is what is known as an [[expansion card]]. This means that the card can be added to the [[motherboard]]. Nowadays, most of the audio cards are integrated with the motherboard. That means they are built into a [[mainboard]] and can not be removed. In other words, it is not an expansion card anymore. They only offer line-in, [[computer speaker|speaker]], and [[microphone]] connections. For most users this is enough. When thinking of [[computer architecture]], the [[integrated circuit]] sound cards occupy less space and thus became very popular and practical, especially for [[laptop]] computers. For more features like [[MIDI]] ports for connection of musical instruments and low [[latency]] requirements (so that the sound does not come distorted under heavy system usage) sound cards as expansion cards can be used. Modern expansion sound cards use the [[PCI]] [[computer bus]] standard. Earlier sound cards used the [[ISA]] computer bus, which was half-duplex, so the sound cards could not record and play simultaneously. ==Input and output signals== What we hear in speakers is an analog ([[Electric current|current]], [[voltage]] or [[electric charge]]) output of the signal. For example, stored on a [[hard disk]] digital code is transferred under a control of some application (for example [[Winamp]]) to the sound card. Up in there, a special chip, called [[digital-to-analog converter]], changes the [[binary code]] into the analog sound. Afterwards, signal is sent to a [[jack]] (in modern audio cards it has the green color) where the speakers are connected. The result is a nice [[waveform]] of our favorite digital medium, e.g. an [[mp3]]. A typical sound input device is a microphone, connected to the red/pink jack socket. The sound wave is digitized and then it may be stored as a [[comp