Compressors

Compressors are designed to manage the dynamic range of an audio signal. A compressor accomplishes this by reducing the gain of a signal that is above a defined level (threshold) by a defined amount (ratio). Without this gain reduction, a signal that gets, say 10% louder as an input, will be 10% louder at the output. With the gain reduced, a signal that gets 10% louder at the input will be perhaps 3% louder at the output. Most compressors available are designed to allow the operator to select a ratio within a range typically between 1:1 and 20:1, with some allowing settings of up to ∞:1. A compressor with an infinite ratio is typically referred to as a limiter. The speed that the compressor adjusts the gain of the signal (called the attack) is typically adjustable as is the final output of the device.

Compressor applications vary widely from objective system design criterion to subjective applications determined by variances in program material and engineer preference. Some system design criteria specify limiters for component protection and gain structure control. Artistic signal manipulation is a subjective technique widely utilized by mix engineers to improve clarity or to creatively alter the signal in relation to the program material. An example of artistic compression is the typical heavy compression used on the various components of a modern rock drum kit. The drums are processed to be perceived as sounding more punchy and full.