DRC (dynamic range compression) referred as compression, is a useful process in which the dynamic range of any given audio signal is reduced or, in other words, the gap between low and high audio levels is narrowed down. This process is generally used in broadcasting, live sound reproduction and sound recording. The application of compression is achieved by passing any given audio signal straight through an electronic hard ware unit, or in some cases, through a carefully programmed software. In terms of audio signals, this device is known as a compressor.
Features and uses:
In normal terminology, a compressor is nothing but a device that controls volume automatically. There are two kinds of compression namely, downward compression and upward compression. When downward compression is used, the levels of loud sounds above a particular threshold get reduced. However, the quieter sounds remain untouched. On the contrary, upward compression, when used, makes the sounds that are under the threshold loud leaving the louder sounds untouched. In both the instances, the dynamic range of the audio signal is reduced. This is generally done to minimize the effects of the various limitations present in audio equipment. Compression may help in increasing the audibility of the audio in surroundings where the noise level is substantially high. Generally, in these kinds of places, the background noise could overshadow quiet sounds. If compression is used to reduce the level of louder sounds without affecting the gain of quieter sounds, then the level could be elevated to such a point that the quiet sounds can be audible without louder sounds being intolerably loud. Basically, a compressor is used to reduce the gain of any given audio signal if its amplitude overcomes a particular threshold. The level of reduction is obtained by a fixed ratio. If the fixed ratio is 4:1, it means, if the input gain is 4dB, then, the output gain would have to be 1dB over the threshold.
Compressors often come with additional, useful controls such as release and attack. These controls help in slowing down the response speed of any given circuit. This helps in smoothing the sound effects.