Apple Final Cut Pro 7 - Manual (Page 875)

Acceptable amount of dynamic range Venue
20 dB Theatrical Dolby Digital
12 dB Average videotape
6 dB Television broadcast
When you mix your final audio, you choose a consistent reference for the average level.
When you choose the average reference level, you are actually choosing how much
additional headroom you have before your signal distorts. The higher you set the average
level, the less safety margin you have for peaks in the signal. This means that the loudest
sounds in your mix cannot be much louder than the average levels, so the mix is less
dynamic.
If you set the reference level of the Final Cut Pro floating audio meters to -20 dBFS, you
have nearly 20 dB of headroom because 0 dBFS is the digital limit for the loudest sound.
If you set the reference level in your sequence to -12 dBFS instead, you have less
headroom. Even though the average level of your audio is higher, there won’t be as much
dynamic range.
Available headroom with
a reference level of –12 dBFS
−66
−36
−24
−18
−12
−6
0
−48
How much dynamic range you allow in your audio mix depends on its ultimate destination.
If you’re editing a program for TV broadcast, a reference level of -12 dBFS is fine, because
you are only allowed 6 dB of dynamic range anyway. But if you’re working on a production
to be shown in movie theaters, consider using a reference level closer to -18 or even -20
dBFS (both of these are frequently used standards).
Remember that the ultimate goal is to ensure that audio doesn’t peak over 0 dBFS in
your mix (as displayed in the Final Cut Pro audio meters) and won’t peak over +3 dB or
so on an analog meter.
875 Chapter 54 Evaluating Levels with Audio Meters