Gone are the days that computers could only beep at different frequencies and duration; when sound card technology began to surface in the 1980’s, we launched into an era in which computers could provide top-tier audio for music, movies, video games, and whatever other media in which a user might be interested. With the help of sound cards, computers can even capture and record sound from external sources. If you’re interested in what sound cards are and how they work, read on for an introduction to the important computer component.
The challenge behind computing sound involves the fundamental difference between the way we’re used to recording computer-related data and sound-related data. Sounds are analog, meaning they are thought of as waves that travel through matter. We hear sounds when these waves travel through the air and vibrate our eardrums.
Computers communicate digitally, meaning they use electrical impulses that stand for a binary code of 0s and 1s. In order for computers to create a sound, or for sound to be recorded onto a computer, it was necessary to create a bridge between these analog and digital worlds.
Enter the sound card. The sound card acts as a translator behind the analog information of sound and the digital information with which computers can work. Basic sound cards are printed circuit boards that use four main components to complete this process: an analog-to-digital converter (ADC), a digital-to-analog converter DAC), an ISA or PCI interface that connects the sound card to the motherboard, and input and output connections for microphones, speakers, amplifiers, and the like. It’s also common for some sound cards to use a coder/decoder chip called a CODEC to perform both of the ACD’s and DAC’s functions.
So let’s walk through the processes by which a sound card does its job. Say you want to make a recording of yourself speaking; when you speak into a microphone connected to your sound card, the ADC translates the analog sound waves of your voice into digital data that the computer can work with. In other words, the sound card samples, or digitizes, the sound of your voice by taking very precise measurements of the wave at frequent intervals.
Now that you’ve made your recording, say you want to hear it played back to you through your computer’s speakers. That’s where the DAC comes in; it performs the same basic steps as the ADC, but in reverse. In other words, it reads the digital information stored in your computer and creates the sound of your voice accordingly.
High quality systems with high sampling rates can make and play back an almost identical replica of your voice, but no system functions without reducing sound quality to some extent. The process of recording and playing back your voice can also cause distortion. There are two measurements used by manufacturers to measure the reduction in sound quality: total harmonic distortion (THD), which is measured as a percentage, and signal to noise ratio (SNR), which is measured in decibels.