How Sound Cards Work

A sound card must translate between sound waves and bits and bytes.

Analog vs. Digital

Sounds and computer data are fundamentally different. Sounds are analog - they are made of waves that travel through matter. People hear sounds when these waves physically vibrate their eardrums. Computers, however, communicate digitally, using electrical impulses that represent 0s and 1s. Like a graphics card, a sound card translates between a computer's digital information and the outside world's analog information.

Sound is made of waves that travel through a medium, such as air or water.

The most basic sound card is a printed circuit board that uses four components to translate analog and digital information:

  • An analog-to-digital converter (ADC)
  • A digital-to-analog converter (DAC)
  • An ISA or PCI interface to connect the card to the motherboard
  • Input and output connections for a microphone and speakers

Instead of separate ADCs and DACs, some sound cards use a coder/decoder chip, also called a CODEC, which performs both functions.

In the next section, we'll explore the analog-to-digital and digital-to-analog conversions that take place on the sound card.