AskDefine | Define headroom

Dictionary Definition

headroom

Noun

1 vertical space available to allow easy passage under something [syn: headway, clearance]
2 the capacity of a system to reproduce loud sounds without distortion [syn: dynamic headroom]

User Contributed Dictionary

English

Noun

  1. the vertical clearance above someone's head, as in a tunnel, doorway etc
  2. the ability of a system to reproduce loud sounds free of distortion; dynamic headroom

Extensive Definition

contradict-other Loudness War
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.
Failure to provide adequate headroom is a common problem with CDs published in the late 1990s and early 2000s which often use heavy level compression (not to be confused with data compression by codecs such as MP3), producing a very flat 'mushy' sound that lacks the sparkle provided by brief peaks from percussion sounds. See Loudness war.
AL = analog level SPL = sound pressure level
headroom in German: Aussteuerungsreserve
headroom in Italian: Headroom
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