Apple Final Cut Express 4 - Manual (Page 605)

Chapter 41 Evaluating Levels with Audio Meters 605
VIII
Important: Final Cut Express can handle digital audio levels above 0 dBFS by internally
using 32-bit floating-point resolution for all audio processing. However, when you
export or output to tape, the bit depth of your audio is usually reduced to 16 or 24 bits,
so you still need to be aware of the 0 dBFS limit.
Original
0 dBFS 0 dBFS 0 dBFS
Too much gain
causes clipping Clipping remains
after gain is reduced
Analog 0 dB Versus Digital 0 dBFS
Even though audio is exclusively digital in Final Cut Express, it is likely that your audio will
exist in an analog context at some point. Most digital workflows begin with microphones
and end with speakers, which are both analog devices.
On an analog meter, 0 dB is the optimal recording or output level of a device. If the
voltage is much higher, it may distort. If it is much lower, it may be lost in the noise
inherent in the device. On a digital meter, 0 dBFS refers to the highest audio level
allowed before clipping.
When you look at the meters in Final Cut Express, you need to consider how the
signal level will correspond to an analog meter. Specifically, you need to choose a
point on the digital meter that corresponds to 0 dB on an analog meter. This point is
where your average signal level should be, providing headroom for occasional peaks.
Headroom is particularly important in digital audio because any audio that goes
beyond 0 dBFS during export or output instantly clips and sounds distorted.
The level you choose for your average audio level affects the potential dynamic range
of your mix. The lower your average signal is allowed to be, the greater the difference
between the average and loudest sounds, providing a larger dynamic range.
However, you should also choose an average level that allows a significant difference
between your quietest sounds and the noise floor.
There are several common digital levels used to correspond to 0 dB on an analog meter:
 –12 dBFS: This level is often used for 16-bit audio such as DV audio, and for projects
with compressed dynamic ranges, such as those for television or radio.
 –18 or –20 dBFS: This level is more common on projects with higher dynamic range,
such as professional post-production workflows using 20- or 24-bit audio.