Sibilance is the harsh, hissing sound created by certain letters and combinations of letters when they're pronounced. The letters S, Z, SH, CH, and J are the most common sources of sibilance. Sibilance can be a problem when recording or broadcasting audio because it can make speech difficult to understand. It can also be distracting to listeners. In some cases, it can even be painful to listen to. That's why many broadcasters and voice-over artists try to avoid sibilant sounds whenever possible. To avoid sibilance, they might use a de-esser, a type of audio processing plugin that can reduce or eliminate the harsh, hissing sounds of sibilance.