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Computer Audio Tutorial


No computer is complete without sound. From listening to our favorite tunes to playing the latest, most popular video games, sound makes our computer experience fun. All this is done with a sound card.

Sound Card

In the natural world, sound travels in waves. We refer to these waves as analog. Computers only understand digital, or 1's and 0's. Sound card technology converts analog sound, such as from a microphone or other source, to digital, then back to analog for output through speakers or headphones. While being converted to digital, sound effects or other enhancements are added before being sent to speakers.

To achieve this, some cards have an ADC and a DAC chip on them. ADC stands for analog to digital converter and, as you might guess, DAC is for digital to analog converter. If they do not have these chips, a codec is used to accomplish the same thing. However, this codec is not the same as one used to convert from one file type to another, such as from mp3 to wav. So don't confuse them. Sound cards may have their own processor, called a digital signal processor (DSP) to take some of the load off the CPU. If there is no DSP, the card uses the computer's processor. They may also have their own memory.

Practically every board today has on-board sound. However, as I mentioned on another page, you can use an expansion slot to have your own card added. There are also external sound cards that connect through a USB port. Some people like buying their own card because many of them have more features than what's on a motherboard. But whichever you choose, there are three common ports: Line-In, Line-Out, and Mic.

Audio Ports

  • Line-In: This port is where sound from an external source enters the card, such as recording from a tape recorder. On many sound cards this port is light blue.
  • Line-Out (Speaker Out or Front): Where sound is output; usually to headphones or stereo speakers. On many cards this port is lime green.
  • Mic: Microphone port; usually pink.
Other Ports:
Game/MIDI port: The MIDI port is a dual-purpose port used to connect a joystick, electronic instruments or a synthesizer. MIDI stands for Musical Instruments Digital Interface. Nowadays it is not available on all sound cards. Its color is usually yellow.

SPDIF Port: Stands for Sony/Philips Digital Interface - Remember, the job of a sound card is to convert audio from analog to digital then back to analog so it can be played through speakers. Well with a SPDIF port, everything is digital, from the input of sound to the output to the speakers. Connectors can be either RCA or optical. RCA ports are round and use coax cable. Optical ports are small and square and use a TOSLINK fibre optic cable. They are labeled optical in and optical out. Some cards come with RCA and optical connectors.

Surround Sound:
Going to the movies has long been a favorite pastime. We went from silent movies to sound. As time advanced, so did the improvement of theater audio. Eventually, a night at the movies became more enriching because the sound encompassed the audience - it came from all directions. This enveloping effect is what's known as surround sound and is supported by many of today's audio cards.

Surround sound cards provide computer owners with the same audio experience that's at the movies. They utilize multiple speakers positioned behind as well as in front and to the sides of listeners. As of this writing, the most popular types are 5.1, 6.1, and 7.1. The number in front represents how many speakers there are. The .1 channel is for extremely low bass called LFE (Low Frequency Effects), which is usually sent to the subwoofer. Below is a description of the different types:
  • 5.1 - In a 5.1 surround sound system, there are five speakers: a left front and a right front speaker, a center speaker, surround left and surround right speakers. Dolby Digital (aka AC 3) and DTS formats support 5.1.
  • 6.1 - 6.1 surround has the same speakers as in 5.1 except it adds a surround back speaker. Dolby Digital EX (Extended), THX Surround EX and DTS-ES formats support 6.1.
  • 7.1 - In a 7.1 setup the same standard five speakers are used as in 5.1 with a surround back left and surround back right speaker added. Dolby True HD supports 7.1.
Back of a sound card

Let's look at some sound card technology by Creative Labs that enhances surround sound on a computer.

  • X Fi (Extreme Fidelity): An audio processor that improves sound in music, movies, and games and can transform stereo music into surround sound.
  • X Fi Crystallizer: X Fi Crystallizer re-masters damaged parts of audio. In addition to that, instruments, particularly the bass, are much more enhanced and clearer.
  • X Fi CMSS 3D Virtual: Don't have a surround sound setup. No problem. CMSS 3D Virtual turns a two-speaker system into surround sound by providing seven virtual speakers.
  • X Fi CMSS 3D Headphone: Similar to 3D Virtual. Makes your headphones play surround sound with nine virtual speakers.
  • X Fi-RAM: 64MB of memory that currently exists on Sound Blaster X Fi Fatal1ty and Sound Blaster X Fi Elite Pro cards only. X Fi also uses EAX (Extended Audio Extensions), which makes games come alive by providing super real life-like sounds. Also, just as in a movie, the music changes according to what's taking place while you're playing. For instance, the music may sound alarming if the enemy is around or sad if your character dies. Developed in 1998, there have been several versions. Below are some features of EAX Advanced HD 5.0, the latest as of this writing.
  • EAX Pure Path: Produces Dolby Digital and DTS surround sound in games just as you hear at the movies.
  • EAX Macro: Produces extremely close-up sounds as if they are right next to you. It practically puts the player in the game.
  • EAX Voice: A gamer can attach a microphone to an EAX device so that he can hear his voice with the same type of effects as those in the game itself.
  • Environment FlexiFX: Allows for major improvement in sound effects.
External Sound Cards:
External USB sound cards are also available. They provide excellent audio quality like internal add-in cards. Many have 5.1 and 7.1 surround sound capabilities as well as the standard two speaker setup. Some are as small as your finger. These are especially handy for those who want to add their own card but are not tech savvy enough to install an internal one or don't have the money to pay a tech to do it for them.







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