What is the role of a de-esser plugin in vocal processing, and how does it work to reduce sibilance?

The role of a de-esser plugin in vocal processing is to reduce sibilance, which are the harsh, hissing sounds that often occur when a vocalist pronounces 's', 't', 'sh', 'ch', and 'z' sounds. Sibilance can be particularly noticeable and distracting in vocal recordings, especially after compression or EQ has been applied. A de-esser works by detecting these high-frequency sibilant sounds and then applying gain reduction to those frequencies, thereby reducing their prominence in the overall vocal signal. Typically, a de-esser consists of a sidechain circuit that is sensitive to a specific frequency range, usually between 4kHz and 10kHz, where sibilance is most prevalent. When the level of the signal in this frequency range exceeds a set threshold, the de-esser activates and applies gain reduction to that same frequency range. Some de-essers use a broadband gain reduction, meaning they reduce the overall level of the signal when sibilance is detected, while others use a frequency-specific gain reduction, targeting only the sibilant frequencies. The key parameters of a de-esser include the threshold (the level at which the gain reduction begins), the frequency (the center frequency of the sibilance range), the range (the amount of gain reduction applied), and the attack and release times (how quickly the de-esser reacts and recovers). By carefully adjusting these parameters, it's possible to reduce sibilance without significantly altering the overall tone or character of the vocal. Incorrect settings, like an overly aggressive reduction or wrong frequency range, can result in a lisping or muffled sound, so subtle and precise adjustments are key.