Dictionary Definition
headroom
Noun
2 the capacity of a system to reproduce loud
sounds without distortion [syn: dynamic
headroom]
User Contributed Dictionary
English
Noun
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
See also
External links
- EBU Recommendation R68-2000
- AES Preprint 4828 - Levels in Digital Audio Broadcasting by Neil Gilchrist (not free)
- EBU Recommendation R117-2006 (against loudness war)
- AES Convention Paper 5538 On Levelling and Loudness Problems at Broadcast Studios
- EBU Tech 3282-E on EBU RDAT Tape Levels
- EBU R89-1997 on CD-R levels
- AES17-1998 (r2004): AES standard method for digital audio engineering -- Measurement of digital audio equipment
headroom in German: Aussteuerungsreserve
headroom in Italian: Headroom