With each year we see more computers move from the office into the living room, becoming a key to multimedia home entertainment centers. They are gradually replacing stereo systems and video players, and
even karaoke machines and televisions.
Accessing these new uses for computers requires specialized components called video cards and sound cards. Even though
most computer motherboards have built-in sound capacity, you really need to add an improved sound card in order to gain access to
these advanced audio features.
Audio Cards
The standard built-in sound processor on computer motherboards is called AC 97. This typical sound system supports DVD (96
kHz, 16 bits, six channels) audio. The AC 97 built-in connections are somewhat noisy as a rule and the resulting quality is really
unsuitable for high fidelity applications.
Unless you're a musician or video editor looking for a professional sound quality card capable of multi-track recording, there are appropriate no-frills cards that will do the job.
To improve the sound over the AC 97 specs and add features, install a third-party audio card in one of the PCI slots of
your motherboard. The type of card that you need to buy depends on what you want to do. If you just want to watch DVDs, get a basic
card. To record music, or connect a microphone, you'll need a more advanced card.
Digital Audio
All information in computers is digital, so sound must also begin in a digital format. Before we can hear it, the digital
audio has to be converted to analog.
We're all familiar with digital audio because of the popularity of CDs. Until the 1980s, with the introduction of CDs,
nearly all sound was analog. An analog sound signal is a continuous representation of sound. Digital audio tries to recreate analog
signals as closely as possible. No matter what the conversion is, there remains missing audio information in a digital
signal.
The analog signal is broken up into individual steps. The CD audio standard is 44.1 kHz at 16 bits. This means there are
44,100 steps per second. Each step can be symbolized with a number up to 16 bits (65,536). DVD (96 kHz at 16 bits) and DVD audio
(192 kHz at 24 bits) are other digital audio standards.
Digital audio must be converted into an analog signal with a DAC (Digital Audio Converter) to be heard, DAC quality varies
significantly, which is a major factor in determining the cost of sound cards.
Things To Consider
The published specifications of sound cards provide a good idea of their level of quality. An essential number to look for
is the S/N, or signal to noise ratio. The higher the S/N, which compares the audio signal with the background noise ratio, the
better the quality. The S/N is expressed in decibels (db) and should be at least 90db. Professional cards, for example, are
frequently rated at more than 100db.
Also important is the number of channels the sound card supports. Surround-sound cards are available in 5.1 or 6.1 and 7.1
configurations. The first number tells you how many satellite speakers can be placed around the listening area. The .1 indicates
the subwoofer channel used for low-frequency sounds.
The cost of audio cards is another good clue as to their quality. Basic cards that begin at $10 have a poor sound quality,
while a $50 card is pretty decent.
If you want to record sound through your computer, you'll also need to look at the number of inputs the sound card has.
Standard inputs are one stereo pair. Cards designed for recording studios have up to 10 inputs. Professional sound cards go for
about $400.
