Audio
Crest Factor / Headroom
01 — Definition
The gap, in dB, between a signal's peak level and its RMS (average) level. Music has a high crest factor — transient peaks rising well above the average; a sine wave sits at 3 dB, and heavily compressed pop can drop under 6 dB. Hence the need to reserve headroom above the working RMS level to pass peaks cleanly: an amp or converter that clips them destroys the transients, even when the average level looks safe.
02 — In the field
Leave enough headroom above your nominal RMS for the programme crest factor — 12–18 dB for live music. A system metering fine on averages can still clip snare and kick transients if headroom is too tight.