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This article is about the digital 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 decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to The EBU specifies a PML of 9 dB below 0 dBFS (-9 dBFS), thus giving 9 dB of headroom. dBFS means " Decibels Full scale " It is an abbreviation for decibel amplitude levels in digital systems which have a maximum available level (like PCM

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. The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to 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. The 1990s collectively refers to the years between and including 1990 and 1999 Dynamic range compression, also called DRC (often seen in DVD player settings or simply compression, is a process that reduces the Dynamic range of For processes which reduce the amount of time it takes to listen to and understand a recording see Time-compressed speech. A codec is a device or program capable of encoding and/or decoding a Digital Data stream or signal. MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a Digital audio encoding format using a form of Lossy data compression See Loudness war. The phrase loudness war (or loudness race) refers to the Music industry 's tendency to record produce and broadcast music at progressively increasing levels of

AL = analog level SPL = sound pressure level

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Audio quality measurement seeks to quantify the various forms of corruption present in an audio system or device Noise measurement is carried out in various fields In Acoustics, it can be for the purpose of measuring Environmental noise, or part of a test procedure using Programme level refers to the level that an Audio source is transmitted or recorded at and is important in audio if listeners to CD 's Radio and Television Rumble measurement is carried out on turntables (for vinyl recordings which tend to generate very low frequency noise originating from the centre Bearing and from The ITU-R 468-weighting curve (originally defined in CCIR recommendation 468 is widely used when measuring noise in audio systems especially in the UK Europe and former countries of A-weighting is the most commonly used of a family of curves defined in the International standard IEC616722003 and various national standards relating to the measurement of sound A weighting filter is used to emphasise or suppress some aspects of a phenomenon compared to others for measurement or other purposes An equal-loudness contour is a measure of sound pressure ( dB SPL) over the Frequency spectrum for which a listener perceives a constant loudness The Fletcher–Munson curves are one of many sets of Equal-loudness contours for the human ear determined experimentally by Harvey Fletcher and W A Munson and The phrase loudness war (or loudness race) refers to the Music industry 's tendency to record produce and broadcast music at progressively increasing levels of

Dictionary

headroom

-noun

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