One of the biggest problems with audio quality, especially in a home pc recording studio, is noise. Cheap microphones are notorious for creating lots of hiss along with the thing you ACTUALLY wanted to record. If you use a computer for recording, you get a big slice of computer fan and drive noise along with your serving of hiss. So what can you do about it?
The best way to avoid noise problems is to prevent as much of it getting into your recording as possible. But for this article, we're talking about audio that ALREADY has noise in it. So let's use an example that is very common...a recording of a human voice, likely for a podcast or to narrate a video. The same concepts hold true for any audio though.
Let's say you recorded your voice on your computer for a podcast you're producing. Play the audio and watch/listen (you can do both nowadays thanks to software editors!) for the areas where you are NOT talking. You should here some of that hiss and other junk we mentioned above. If you don't, try listening in headphones. Whoa! There it is. Wow, huh? There are two ways to deal with this. Or you could use them in combination.
The first treatment is called "noise reduction." This is where the audio editing software basically "washes" the noise off of the audio, like washing dirt off your car. To do this, you need to tell the program what the dirt looks like, so it can tell the difference between your voice (which you want to keep), and the noise (which you want gone). This is why you need to find a second or two of the audio file where you are NOT talking. Theoretically that section should be 100 percent noise. Then the program will go through the entire audio file getting rid of the stuff that looks like the sample you fed it, while doing its best to leave your voice alone. There are all kinds of parameters you can adjust to fine tune the results.
The second treatment is called a "noise gate." This tool, also found in the audio program, will put a barrier at a volume setting just above the loudest section of noise. No sound less than the barrier volume is will be heard, but sounds that are louder will be allowed through. The idea is that the sections of the audio where there is no talking will be silenced, but when the talking starts, the barrier opens like a gate, letting it pass through and be heard. The gate is constantly opening and closing as the volume gets louder and softer.
One problem you can have with a noise gate is that you can still hear the hiss when the voice is talking, since the loud stuff does not get treated. Often times the marked difference between the silence between the talking bits, and the hiss during the talking can be really jarring, actually calling attention to the fact that there is lots of hiss in the recording. Gating works best if there is other audio, such as background music, behind the vocal part, masking the hiss.
So there you have it. If your audio has hiss and other gunky sounds in it, use noise reduction, a noise gate, or some combination of the two to create much higher quality audio. Check out our tutorials on noise and all things "home recording."