Apple Final Cut Express HD - Manual (Page 598)

598 Part VIII Audio Mixing
Setting Proper Audio Levels
When you work with audio, you need to make sure you set proper levels during
capture, mixing, and output.
Setting Levels for Capture
When you capture digital audio, you usually cannot make level adjustments because an
exact copy of the digital information is transferred to your hard disk. However, if you are
capturing analog audio using the Voice Over tool, make sure you set the levels so the
meters in the Voice Over tool match the audio meters on your video or audio device.
What Reference Level Should You Use for Mixing?
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, which
reduces 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, and so
the mix is less dynamic.
Venue Acceptable amount of dynamic range
Theatrical Dolby Digital 20 dB
Average videotape 12 dB
Television broadcast 6 dB