Reference Level

A reference level is a defined anchor point that represents a reasonable or typical level allowing for sensible headroom management. In the United States, this level is typically 0vu, or -20dBFS. This allows for 20dB of headroom before clipping of the audio signal occurs in a digital recording.

This definition/image is licensed under the GNU Free Documentation License found at http://www.gnu.org/copyleft/fdl.html. It uses material from the Wikipedia article at http://en.wikipedia.org/wiki/Alignment_level.