headroom

n. space above the head (in a doorway, car, etc.)

This article is about the audio signal processing term. For other uses, see Headroom (disambiguation). In a digital audio system, headroom is the amount by which digital full scale (FS) exceeds the permitted maximum level (PML) in dB (decibels). The EBU specifies a PML of 9 dB below 0 dBFS (-9 dBFS), thus giving 9 dB of headroom.Alignment level is an 'anchor' point, a reference level which exists throughout the system or broadcast chain, though it may have different actual voltage levels at different points in the analog chain. Typically, nominal (alignment) level is 0 dB, corresponding to an analog sine wave voltage of +4 dBu, or 1.23 Vrms (3.47 Vp-p). In the digital realm, alignment level is −18 dBFS. An alternative EBU recommendation allows 24 dB of headroom, which might be used for 24-bit master recordings, where it is useful to allow more room for unexpected peaks during live recording.
See more at Wikipedia.org...

Noun
1. vertical space available to allow easy passage under something
(synonym) headway, clearance
(hypernym) room, way, elbow room
2. the capacity of a system to reproduce loud sounds without distortion
(synonym) dynamic headroom
(hypernym) high fidelity, hi-fi

(n.)
See Headway, 2.
  

The vertical distance between the top of the superstructure of a vehicle or the head of a person and any obstruction above them. See also overhead clearance. 15/7/2000