Audio level compression, sometimes referred to as DRC (dynamic range compression) is a process which reduces the dynamic range of an audio signal. It is used in the mastering process very mildly to help increase the overall volume of a source track by decreasing the dynamic fluctuations or peaks. Using a high threshold and low compression ratio generally does this.

Compression makes loud sounds softer, right? Sort of. A compressor is also known as a variable gain device. This means the amount of gain used is dependent on the input level. The diagram below illustrates that a level detector checks to see how loud the signal is and then reduces the gain. All of which is predetermined by how much compression is added.

A compressor only weakens the signal when it is above the threshold level. The threshold is determined by the user. For example, if you have a threshold of -1 dB, then any signal over -1 dB will be reduced. But how much it is reduced is controlled by the compression ratio the user has selected. Are there any rules in mastering compression? Bob Katz the mastering guru says, “The first rule is that there are no rules.” He co

ntinues, “If you want to use a compressor/limiter of any type, shape and size in your music, then go ahead and use it.” The goal in mastering a single track or album is different for every project. Some people want their music LOUD and others want it wide and others want it to sparkle. 

“The five tones deafen the ear.” – Lao Tzu