Working Through the Numbers
Sound card manufacturers will generally list screeds of technical information with their products, but this detail can help choose a card to fit your needs. The key points to look for after assessing your connection method (internal or external), and desired connectors are bit and sampling rates, audio channels and signal to noise ratio.
First up, before worrying about signal to noise ratio and bit and sampling rates, you'll have to decide how many channels you'll need. A "channel" refers to the number of discrete speakers supported by the sound card.
A base minimum these days is support for 5.1-channel surround-sound audio (covering two rear speakers, two front speakers, one centre speaker, and one sub-woofer), though 7.1-channel surround-sound audio is becoming popular (this standard includes all the speaker positions defined in 5.1, with the addition of left and right middle speakers). If you're only going to rely on headphones for audio playback, the channel support is a non-issue, but this is crucial if you're going to play back through a surround-sound speaker set or an amplifier.
Sound cards are generally marketed by supported bit rates and sampling rates, which refer to the maximum amount of sound data that the sound card can process per second.
Computers have no way of storing a continuous sound, so audio recorded into a computer is broken up into very small chunks. These small chunks are referred to as sample rate, which is a measure of audio resolution. For example, CDs are sampled at 44.1KHz (or 44100Hz), meaning there are 44100 chunks of sound stored for each second of audio. These discrete chunks are played back very quickly and the human ear recognises it as a sound. This is similar to the way a television works: it shows enough information each second to fool the eye into thinking it's watching moving pictures.
The higher the sample rate for a sound card, the "smoother" the sound, and the closer the digital recording resembles the original analogue sound.
The bit rate of a sound card refers to the amount of information stored in each individual chunk of sound. Bit rate and sampling rate go hand-in-hand and the higher the bit rate, the more accurate the digital recording.
CDs are recorded in 16-bit with a sampling rate of 44.1KHz, so any card with base specifications above that will be able to handle CD-quality playback. If you're just playing back MP3s, playing the occasional game, and covering system alerts, you can get away with a relatively basic card with 16-bit support and a 48KHz sampling rate. Keep a close eye on signal to noise ratio specifications on low-end cards, as this can be a major point of differentiation between models. These basic cards will set you back around $40-80.
If you're into watching DVDs and own a surround-sound amplifier, you're best off opting for a mid-range card with 24-bit support and a 96KHz sampling rate. These cards will generally cost around $200 and offer a signal to noise ratio around 85dB.
Finally, if you want to start producing your own music or take your DVD-watching very seriously, it's time to step up to a bells-and-whistles card with 24-bit support and a sampling rate of 192KHz. These top-of-the-line consumer solutions will offer a signal to noise ratio in excess of 110dB and are ideal for recording music live. Many also ship with external connection boxes and retail at around $500.
Of course, a sound card is only half the battle when it comes to setting your PC up for serious sound. After all, you still need to get the sound from the audio connectors to the airwaves. For best results, focus on buying a speaker combination that matches the audio output from your sound card. For instance, buying a 5.1-channel surround-sound speaker system to use with a 7.1-channel card means that you'll miss out on hearing two audio channels during playback. Shop around and demand information on each speaker in a multi-speaker kit, as total output figures can be misleading. Many speaker companies advertise "total output" across the speakers, but this could mean that the majority of the power is going to driving a huge subwoofer, with little attention paid to satellite speakers.
Last but not least, cast an eye over the list of software bundled with a sound card. Some basic solutions will offer little more than a driver CD, while some more expensive models may include games, music sequencing software and some troubleshooting tools. This can often be a differentiator between products with similar pricing and specifications: if in doubt, go for the card with the stronger software set. If software is irrelevant to your buying decision, hunt around for shops that are offering OEM or value bundles on hardware, as it often means you can get the card without bundled extras to save a little cash.
For more information on sound cards and other audio topics, go to PC World's Digital music section
This guide was last updated June 2005