How Sound Cards Work

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 theireardrums. 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 translateanalog and digitalinformation:

Instead of separate ADCs and DACs, some sound cards use a coder/decoder chip, also called aCODEC, 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.

Imagine using yourcomputerto record yourself talking. First, you speak into amicrophonethat you have plugged into your sound card. The ADC translates the analog waves of your voice into digital data that the computer can understand. To do this, it samples, or digitizes, the sound by taking precise measurements of the wave at frequent intervals.

The number of measurements per second, called thesampling rate, is measured in kHz. The faster a card'ssampling rate, the more accurate its reconstructed wave is.

If you were to play your recording back through thespeakers, the DAC would perform the same basic steps in reverse. With accurate measurements and a fast sampling rate, the restored analog signal can be nearly identical to the original sound wave.

Even high sampling rates, however, cause some reduction in sound quality. The physical process of moving sound through wires can also causedistortion. Manufacturers use two measurements to describe this reduction in sound quality:

For both THD and SNR, smaller values indicate better quality. Some cards also support digital input, allowing people to store digital recordings without converting them to an analog format.

Next, we'll look at the other components commonly found on sound cards and what they do.

In addition to the basic components needed for sound processing, many sound cards include additional hardware or input/output connections, including:

Digital Signal Processor (DSP): Like a graphics processing unit (GPU), a DSP is a specializedmicroprocessor. It takes some of the workload off of the computer's CPU by performing calculations for analog and digital conversion. DSPs can process multiple sounds, or channels, simultaneously. Sound cards that do not have their own DSP use the CPU for processing.Memory: As with agraphics card, a sound card can use its own内存to provide faster data processing.Input and Output Connections: Most sound cards have, at the very minimum, connections for amicrophoneandspeakers. Some include so many input and output connections that they have abreakout box, which often mounts in one of the drive bays, to house them. These connections include:

Game designers use3-D soundto provide fast-paced, dynamic sound that changes based on a player's position in the game. In addition to using sound from different directions, this technology allows realistic recreations of sound traveling around or through obstacles.Surround soundalso uses sound from several directions, but the sound does not change based on the listener's actions. Surround sound is common inhome theatersystems.

Like agraphics card, a sound card uses software to help it communicate with applications and with the rest of the computer. This software includes the card's drivers, which allow the card to communicate with theoperating system. It also includesapplication program interfaces(api),设置的规则或标准make it easier for software to communicate with the card. The most common APIs include:

Not every computer has a sound card. Some motherboards feature integrated audio support instead. Amotherboardthat has its own DSP can process multiple data streams. It may also support 3-D positional and Dolbysurround sound. However, in spite of these features, most reviewers agree that separate sound cards provide better audio quality.

Laptops usually have integrated sound capabilities on their motherboards or small sound cards. However, space and temperature control considerations make top-of-the-line internal cards impractical. So,laptopusers can purchase external sound controllers, which useUSBorFireWireconnections. These external modules can significantly improve laptop sound quality.

For more information on sound cards and related topics, check out the links on the following page.