Archive for the ‘How Sound Cards Work’ Category

How Sound Cards Work

Computer Hardware Image Gallery

Computer Hardware Image Gallery

A sound card allows a computer to create and record real, high-quality sound.

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 atCrossfire Designs.


Fortunately, computers’ sound capabilities increased greatly in the 1980s, when several manufacturers introduced add-on cards dedicated to controllingsound. 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.

In this article, you’ll learn how a sound card allows a computer to create and record real, high-quality sound.


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 agraphics 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)
  • 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.