A brief introduction to sound cards and audio interfaces
When you need to get an audio signal out of your computer to some speakers, or get some sound from the outside world into your computer, you need an audio interface.
All computers these days have audio interfaces built into them. They are usually enough to get the job done for most music-making endeavors. To reduce noise, get a clearer sound, and get recorded music to sound nice and open and clear, an external audio interface is usually a good idea. Audio interfaces connect to a computer via USB, Firewire, or have a card in the computer with a cable that hooks into an external box. Here's an example of an external USB/Firewire interface:
On this particular interface, we have input-level trim knobs on the left, speaker volume, and headphone volume.
On the right, there are indicator lights that show us the audio's volume coming in and out of the device. This interface has a pretty nice meter. It has a green area lit up where the audio is at a comfy volume. The yellow area tells us the volume is getting close to peaking and the red area is the audio peak. We don't want audio to peak on input because it will distort. We also don't want it to peak the output, because it will distort as well.
An external audio interface like this gives us a lot of information. If you are using an internal soundcard that came with your computer, you are going to have to rely on the meters in the software you are using and your ears to tell you whether your volume is too loud or not.
