An audio leveler performs an audio process similar to compression, which is used to reduce the dynamic range of a signal, so that the quietest portion of the signal is loud enough to hear and the loudest portion is not too loud.

Levelers work especially well with vocals, as there are huge dynamic differences in the human voice and levelers work in such a way as to sound very natural, letting the character of the sound change with the different levels but still maintaining a predictable and usable dynamic range.

A leveler is different from a compressor in that the ratio and threshold are controlled with a single control.

Levelers sometimes feature only an overall gain and peak level control (aka normalization control) on particular models to more accurately and subtly manage peak volume.