What does a compressor do for voice recordings?
Whether you make animations, deliver voice-overs or work as a video editor, sooner or later you will run into audio compression. Together with tone control (equalisation), it is one of the most widely used forms of signal processing in audio production, but it is also a technique that often stays abstract as long as you do not understand exactly which problem it solves.
Dynamic range
To understand that properly, it helps to look first at the dynamic range of a voice recording. If you were to draw the volume curve of a spoken text, you would see that the level fluctuates constantly. Some words are spoken more softly, others with more emphasis. The difference between the loudest and the quietest passages is called the dynamic range.
With a voice-over on its own, that does not have to be a problem. But as soon as a voice is combined with music or other audio elements, a large dynamic range can get in the way. It becomes harder to find a stable balance: at some moments the voice is too loud compared to the music, at others too quiet.
That is exactly what a compressor is used for: a compressor reduces the dynamic range of a signal. It does this by setting a threshold. As soon as the audio signal goes above that limit, the compressor automatically lowers the level. Loud passages are brought down a little, while the quieter passages end up relatively closer to that level.
The result is a recording that sounds more consistent and is therefore easier to combine with other elements in the mix.
Because compression initially lowers the signal level, many compressors also have an output gain. This lets you raise the overall level again once the dynamics are under control. That way you get a voice that not only sounds more even, but also has more presence and body in the mix.
After compression and make-up gain
For voice recordings, a relatively simple compressor is often used. A well-known example is Waves Renaissance Vox, usually shortened to RVOX. This plugin combines several functions in a single control, which makes it quick and intuitive to use.
The most important parameter in RVOX is the comp control. It effectively sets both the threshold and the automatic make-up gain. As you add more compression, the signal is not only kept in check dynamically, but also automatically brought back up to level.
By setting the compressor so that it responds lightly to both the louder and the quieter passages, you get a more stable and consistent voice sound. That makes it much easier to find a good balance between speech and background music.
The end result is a voice-over that stays clear, is easy to understand and sits firmly in the mix, without losing the natural dynamics of the voice.
