Alignment level

From Wikipedia, the free encyclopedia

The alignment level in an audio signal chain or on an audio recording is a defined anchor point that represents a reasonable or typical level. It does not represent a particular sound level or signal level or digital representation, but it can be defined as corresponding to particular levels in each of these domains.

For example, alignment level is commonly 0 dBu in broadcast chains in places where the signal exists as analogue voltage. It most commonly is at −18 dB FS (18 dB below full scale digital) on digital recordings for programme exchange, in accordance with EBU recommendations. 24-bit original or master recordings commonly have alignment level at −24 dB FS in order to allow extra headroom, which can then be reduced to match the available headroom of the final medium by audio level compression. FM broadcasts usually have only 9 dB of headroom as recommended by the EBU.

Using alignment level rather than maximum permitted level as the reference point allows more sensible headroom management throughout the audio chain, so that quality is only sacrificed through compression as late as possible.

The more widespread adoption and understanding of alignment level throughout the audio industry could help to solve the Loudness war. CD's in particular have suffered a loss of quality since they were introduced through the widespread use of level compression, which, given their very low noise level is quite unnecessary.^{(Neutrality disputed — See talk page)} The incorporation of (switchable) level compression in domestic music systems and car in-car systems would allow higher quality on systems capable of wide dynamic range and in situations that allowed realistic reproduction. Such compression systems have been suggested and tried from time to time, but are not in widespread use — a 'chicken and egg' problem since producers feel they must make programmes and recordings that sound good in car with high ambient noise or on cheap low-power music systems.