De-Esser compressors work to eliminate or reduce unwanted noise in audio frequencies in vocal tracks caused during recording or mixing processes. It is a useful tool for reducing 'hissing', 'sizzling' and other unwanted vocal sibilance.
De-essing can be achieved by temporarily reducing the high frequency content of in a signal when the unwanted sounds are prevalent.
De-essing is a dynamic process related to the compression of a vocal signal, which only enganges when the level of the vocal track's signal in a set sibilant range exceeds that of the set threshold. This is different from equalization (EQ), but can also be used to reduce sibilant frequencies.