Apple Final Cut Express HD - Manual (Page 596)

596 Part VIII Audio Mixing
About Audio Meters in Final Cut Express HD
Final Cut Express HD uses a peak audio meter, which responds very quickly to the audio
signal, alerting you to potential peaks over 0 dBFS. The meters in Final Cut Express HD
display a peak level indicator, which is a yellow line that shows the most recent peak
level for 3 seconds (assuming a higher peak hasn’t been reached).
The peak level indicator helps you get a sense of the dynamic range of your mix
because you can compare the current levels to the most recent peak. For more
information about peak meters, see “
Average Versus Peak Audio Meters ” on page 594.
0 dB (Analog) Versus 0 dBFS (Digital)
Even though audio is exclusively digital in Final Cut Express HD, it is likely that your
audio will exist in an analog context at some point. Even an entirely digital workflow
begins with microphones and ends with speakers, which are both analog devices.
When you look at the meters in Final Cut Express HD, 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 on the digital meter 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.
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 for television or radio.
 –18 or –20 dBFS: This is more common on projects with higher dynamic range, such
as professional post-production workflows using 20- or 24-bit audio.
What Does 0 dB Mean?
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.