Lexicon Reference Level
Level that is used as a reference point when calibrating or leveling (also called calibrating) systems. This is often specified in a standard or technical guideline.
For the calibration of recording or playback devices, sound carriers are usually available which contain signals recorded at the reference level. Examples are measuring records or measuring tapes. Furthermore, there are calibrated generators with which signals with reference level can be generated. These are built into some instruments as an aid.
The reference level is usually not the maximum level a device is capable of. The maximum level of a device (Limit of Level Control) is the level up to which a distortion-free or low-distortion processing of the audio signal is possible. If this level is exceeded, the distortion increases rapidly (overload). Therefore, in practice, a certain distance is kept to the level limit (Headroom or Level Control Reserve), in order to have room for short-term signal peaks without them being distorted immediately.
Depending on the application, there are various international or national standards and regulations for the reference levels. For the hi-fi sector, for example, the regulations on the Line-Level apply, along with other standards, e.g. for microphones and record players. The reference level is often specially marked on Line Level Meter.
See also the Wikipedia articles: [reference level] and [calibration].