When to Do Signal Processing

When to Do Signal Processing
Given all the signal processing options at our disposal, you may very well ask when they should be done and in what order. There really are no hard and fast rules, though we can provide some guidelines. The thing to remember is that the cumulative effect of all your signal processing is going to depend on how each step in your signal processing affects the next step.

For example, if you recorded your original audio at a low level, you may be tempted to normalize it to start. However, if you're planning to add some EQ, be sure to leave headroom, because you may add to the overall level. If you're going to use compression and EQ, remember that the compression is going to warm up your bottom end and make your audio sound fuller, so you may not need to add too much bottom end. Conversely, because compression is going to fatten your sound, you may be tempted to add a touch of high end to compensate for any lost sparkle.

What Signal Processing Is

When we talk about audio signal processing, we are manipulating level one way or another. For example, when we're equalizing (EQing) a file, we're manipulating the level of particular frequencies to change the tonal quality of the audio. When we use compression, we're turning entire sections of the audio signal up or down, depending on the input level. This may not make complete sense until you've heard these two techniques in action, but it's worth remembering that all we're doing is turning things up and down. It really is that simple. The tricky part is knowing what to turn up or down, and when.

One of the great things about working with audio is that we have such amazingly powerful tools. In the next few pages, you'll see just how malleable audio is. You can make things sound better in many ways and without making things sound unnatural. In fact, we're used to hearing processed audio; virtually all broadcast audio, be it radio or television, is fairly heavily processed.

This is why signal processing is important. We expect a certain level of quality from our audio, particularly in the post-CD world. Gone are the days when people walked around with transistor AM radios with cheap mono earpieces. We're used to high-quality, full-spectrum audio. If your podcast doesn't provide this kind of experience, it sends a none-too-subtle cue: amateur. Think about the difference between a big FM radio station sound and the local community college radio. Some of the difference is the type of programming and the on-air talent, but much of it is just plain inferior processing.

Don't let your podcast fall into that category. You absolutely should be producing a program that sounds at least as good as your local radio station. Anything less is just lazy, and your listeners will know it. Let's start with something we've all probably done unwittingly — equalization.