Far too many editors are afraid to touch audio tools like parametric EQ and compression. It’s unfortunate, since the fundamentals are easy to grasp and the payoff is immediate. This month we’re highlighting moviola.com’s free course on using a compressor to control the dynamics of a soundtrack. It can make the difference between a lackluster voiceover and one that punches through the mix. It can also keep an overenthusiastic performance from jarring your viewers.

Compression in itself is a very simple concept: when sounds get too loud the compressor kicks in, reducing the level of the signal. Somewhat counterintuitively, the effect is to make everything sound louder. Why? Because once you’ve removed those intense volume peaks, the entire audio signal can be boosted to a higher level without risk of clipping.

Why is a compressor so important for film and television work? The most obvious application is voiceover, where compression gives that “radio voice” sound. But equally important is the role compression plays in dialog. In theatrical release you can expect a quiet theater, so the whispers of an actor can be easily comprehended by the theater goers. That’s not the case for TV: loud family rooms make it impossible to hear those same lines. Throw some compression on the dialog track though and now an actor’s whisper and her shout are both intelligible.

There are three main components to a compressor: the threshold, the ratio, and the release. The threshold determines how loud a sound needs to get before its volume is reduced. The ratio sets the size of the volume reduction, and the release determines how long the compression remains “on” after being triggered. This last control is subtle, but important. Too short a release time produces an unnatural “pumping” effect.

There are additional elements to a good compressor: makeup gain, soft knee, attack, hysteresis, and even multiband compression. That sounds like a lot, but really the additional controls are fairly intuitive once explained to you. So why wait? Watch the intro to the series below, then follow the link to the entire course. As with all content on moviola.com, the training is completely free, a gift from the Moviola family to the filmmaking community.

Follow the link to the entire series