Dynamics Processing Effects
Quick Note on Effects
Audio effects are more powerful than ever and can do ridiculously amazing things. However, the best tool to use them properly is your ear. Fortunately for traditional musicians, the best way to train your ear is to perform and attend acoustic performances. Knowing what sounds good is more than half the battle, and completely essential.
The best effects are the ones that come naturally. The quality of performance, space, and equipment can render many effects unnecessary. That being said, they are amazing tools to improve or color a performance.
Dynamics in the Context of Audio
We all know what dynamics are—the varying degrees of musical volume/intensity, usually described as piano, mezzo-piano,
The Mighty Compressor
Compression lowers the dynamic range of the affected audio. It does this by squashing the loudest parts and/or raising the quiet parts of the audio.
Ratio: This determines the overall compression. The first number is how much the signal must go over the threshold for the output signal to raise 1 dB. For example, at 4:1, a signal that is 12 dB over the threshold will be output at only 3 dB over the threshold. 3:1 is fairly common for vocals, but depends largely on the singer’s technique. There is almost always a gain reduction meter that shows how much the compressor is altering the audio. A safe practice is to keep the reduction less than -6 dB, often less. Too much and the song sounds boring and unnatural.
Threshold: The point at which the compressor begins to function.
Attack: The time it takes the compressor to begin affecting the audio. If you want to keep the attack of an instrument at full volume, then have the compressor kick in (as is often the case with drums), you should set the attack for long enough to allow that audio through.
Release: How long the compressor continues to function after the audio drops below the threshold. Too short may sound unnatural, while too long could reduce quiet audio too much.
Knee: The shortest knee kicks in immediately at the threshold and is always reducing at the chosen ratio. A softer knee has a more gradual compression curve that could kick in much sooner than the threshold and gently increases the ratio as the signal gets louder.
Input/Output Gain: Most compressors have an output gain to compensate for the compression. Some also have an input gain, if the signal is too low coming into the compressor (this can be remedied elsewhere though).
Mix: Usually, a compressor affects 100% of the audio it receives. If there is a mix parameter, it’ll let a percentage of the unaltered audio through with a corresponding percentage of compressed audio (always adds up to 100%). Mix parameters are common on many audio effects.
A limiter is simply a compressor with a high ratio (usually 20:1 or infinite). These are usually used to prevent audio
A gate lowers the level of an incoming signal by a set amount the moment it goes below the threshold. For example, if the threshold is set at -30 dB and the attenuation is set at 10 dB, then if the audio dips to -30.5 dB, it’ll be attenuated to -20.5 dB. Gates are often too jarring, but if they’re set right, they can clean up audio nicely. They’re a good way to keep noise, breaths, hum, etc . . . under control without having to automate or clean up every spot.
An expander has a similar function, but the decrease is set to a ratio. It’s basically the opposite of a compressor—the decrease varies with how far under the threshold the audio dips. Expanders are rarely jarring since the expansion doesn’t all happen at once.