Apple Final Cut Pro 6 - Manual (Page 859)

74 Part I Audio Mixing
 Track audio level meter: Each track in the Audio Mixer tab corresponds to a track in
your sequence (or in the Viewer) and has an individual meter with a scale from +12
dBFS to –∞ dBFS (silence). A track audio meter shows the levels of the current audio
clip item in a track. Use these meters to make sure the average level of each clip is
consistent with similar audio material and that peaks are not above 0 dBFS.
Note: The meters in the Audio Mixer can actually display levels above 0 dBFS
because Final Cut Pro mixes audio internally at 32-bit floating-point resolution—
much higher than the 16- or 24-bit audio in typical media files. The high mixing
resolution provides enormous headroom to prevent clipping when multiple audio
tracks are mixed together. However, you should never output a signal that exceeds
0 dBFS on the Master audio meters.
Acceptable range
Clipping range
Acceptable range