What Reference Level Should You Use for Mixing and Output?
The dynamic range of your mix is dependent on the final viewing environment. For
example, movie theaters have large, relatively expensive sound systems that can
reproduce a large dynamic range. Television speakers are much smaller, and often the
listening environment has more ambient noise, so very quiet sounds may not even be
noticeable unless the overall signal is compressed and the level increased, reducing the
dynamic range.
For example, television stations normally accommodate only 6 dB between the average
loudness and the peaks. Dolby Digital feature film soundtracks, on the other hand, can
accommodate up to 20 dB between average and peak levels. This is why loud sounds
in a movie theater sound so loud: they are much louder than the average level.
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.
Venue
Acceptable amount of dynamic range
Theatrical Dolby Digital
20 dB
Average videotape
12 dB
Television broadcast
6 dB
Available headroom with
a reference level of –12 dBFS
–
∞
–66
–36
–24
–18
–12
–6
0
–48
68
Part I
Audio Mixing
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.