An operation of audio signal processing that consist either in reducing the volume of loud sounds or in amplifying quiet sounds. Compression is used in sound recording, music post-production, or broadcasting typically in order to prevent a sound from being too loud. The other common aim of compression is to play with the volume of a sound, especially sounds of percussion instruments, in order to make them sound more strikingly. A hardware or software (plug-in) unit that applies compression is called a compressor.