The De-ess audio plug-in and module in iZotope RX attenuates or reduces sibilance, the harsh high-frequency sounds that come from S, F, X, SH, and a soft C. RX includes two modes for handling sibilance: Classic and Spectral. Classic Mode detects sibilants and attenuates them with a broadband gain envelope. Spectral Mode is more transparent, intelligent, and frequency-specific than Classic Mode. Spectral Mode only attenuates the high frequencies where sibilance is most active, leaving the lower frequencies untouched.