De-esser

A de-esser is both a tone- and a volume-based plug-in, used to reduce excessive sibilance in a vocal recording.

Sibilance is the high-end tonal harshness (the hiss) of the human voice associated with the expression of particular consonants, like “f,” “s,” and “t,” that can ruin an otherwise good recording. It is typically found somewhere between 5-10 kHz. A de-esser is a special kind of dynamics processor that focuses on and compresses only the part of the frequency spectrum mostly impacted by sibilance. It’s basically a high-end single-band compressor with an adjustable bandwidth.

De-essers come in all shapes and sizes, but they will always have at least a couple of parameters. Measured in Hz or kHz, any parameters regarding "frequency" are used to determine which part of the frequency spectrum will be compressed.

Like other compressors, some de-essers will have a “threshold” parameter, used to determine the level at which the de-essor begins to compress the signal. Typically measured in dB, any parameters regarding gain are used to determine how much "reduction" to apply to any audio that crosses the threshold within the specified frequency band.

A de-esser might not be necessary or even preferable in every mix and can significantly impact the tone and/or overall volume of a track, which can make a bad recording worse. A “reduction” set too high, for instance, can make a vocalist sound like he or she has a lisp. This tool should be used cautiously and discriminately, and only once it is fully understood. Ideally, your recordings should sound good enough to begin with that you don't need to consider the use of a de-esser, but it's an effective tool for a bedroom producer in a pinch!