The DeEsser is a frequency-specific compressor, designed to compress a particular frequency band within a complex audio signal. It is used to eliminate hiss (also called sibilance) from the signal.

The advantage of using the DeEsser rather than an EQ to cut high frequencies is that it compresses the signal dynamically, rather than statically. This prevents the sound from becoming darker when no sibilance is present in the signal. The DeEsser has extremely fast attack and release times.

When using the DeEsser, you can set the frequency range being compressed (the Suppressor frequency) independently of the frequency range being analyzed (the Detector frequency). The two ranges can be easily compared in the DeEsser’s Detector and Suppressor frequency range displays

The Suppressor frequency range is reduced in level for as long as the Detector frequency threshold is exceeded.

The DeEsser does not use a frequency-dividing network—a crossover utilizing lowpass and highpass filters. Rather, it isolates and subtracts the frequency band, resulting in no alteration of the phase curve.

The Detector parameters are on the left side of the DeEsser window, and the Suppressor parameters are on the right. The center section includes the Detector and Suppressor displays and the Smoothing slider.

Figure. DeEsser window.
DeEsser Detector Section
  • Detector Frequency knob and field: Sets the frequency range for analysis.
  • Detector Sensitivity knob and field: Sets the degree of responsiveness to the input signal.
DeEsser Suppressor Section
  • Suppressor Frequency knob and field: Sets the frequency band that is reduced when the Detector sensitivity threshold is exceeded.
  • Strength knob and field: Sets the amount of gain reduction for signals that surround the Suppressor frequency.
  • Activity LED: Indicates active suppression in real time.
DeEsser Center Section
  • Detector and Suppressor frequency displays: The upper display shows the Detector frequency range. The lower display shows the Suppressor frequency range (in Hz).
  • Smoothing slider: Sets the reaction speed of the gain reduction start and end phases. Smoothing controls both the attack and release times, as they are used by compressors.