Headroom

In digital and analog audio, headroom refers to the amount by which the signal-handling capabilities of an audio system exceed a designated nominal level.^[1] Headroom can be thought of as a safety zone allowing transient audio peaks to exceed the nominal level without damaging the system or the audio signal, e.g., via clipping. Standards bodies differ in their recommendations for nominal level and headroom.

Digital audioEdit

In digital audio, headroom is defined as the amount by which digital full scale (FS) exceeds the nominal level in decibels (dB). The European Broadcasting Union (EBU) specifies several nominal levels and resulting headroom for different applications.

Application	Headroom
FM broadcasts	−9 dBFS
Digital broadcasts and ordinary digital recordings	−18 dBFS
Original master recordings	−24 dBFS

Analog audioEdit

In analog audio, headroom can mean low-level signal capabilities as well as the amount of extra power reserve available within the amplifiers that drive the loudspeakers.

Alignment levelEdit

Alignment level is an anchor point 9 dB below the nominal level,^{[citation needed]} a reference level that exists throughout the system or broadcast chain, though it may imply different voltage levels at different points in the analog chain. Typically, nominal (not alignment) level is 0 dB, corresponding to an analog sine wave of voltage of 1.23 volts RMS (+4 dBu or 3.47 volts peak to peak). In the digital realm, alignment level is −18 dBFS.

• AL = analog level
• SPL = sound pressure level

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.