The De-esser automatically reduces sibilance in the audio signal. Sibilance is most commonly caused by "ssss"’ sounds, and sometimes also by "t", "‘f" and "‘d" sounds. The sibilance generally occurs in the 2 kHz to 10 kHz frequency band, and this is where the Sabine De-esser does its work. The algorithm works by dynamically comparing band-specific and associated harmonic energy levels to the total signal energy. When spikes are detected that correspond to sibilance, a shelving filter is imposed on the appropriate frequency bands, and remains in place for the duration of the sibilance. High frequency energy levels that remain below the comparison threshold do not trigger de-essing, and lows and highs outside the sibilance range are also passed unprocessed and unaffected. This means the Sabine De-esser is effective, but transparent.
Turning the De-esser knob clockwise will increase the amount of sibilance reduction, by increasing the maximum depth of the shelving filter. The maximum allowable cut is 24 dB.