Apple Final Cut Pro 7 - Manual (Page 837)

The goal is to make the quiet sounds (in this case, the crickets) louder so they can compete
with the ambient noise in the listening environment. One approach to making the crickets
louder is to simply raise the level of the entire soundtrack, but when you increase the
level of the quiet sounds, the loud sounds (such as the train) get too loud and distort.
Instead of raising the entire volume of your mix, you can compress the loud sounds so
they are closer to the quiet sounds. Once the loud sounds are quieter (and the quiet
sounds remain the same level), you can raise the overall level of the mix, bringing up the
quiet sounds without distorting the loud sounds.
When used sparingly, compression can help you bring up the overall level of your mix
to compete with noise in the listening environment. However, if you compress a signal
too far, it sounds very unnatural. For example, reducing the sound of an airplane jet
engine to the sound of a quiet forest at night and then raising the volume to maximum
would cause the noise in the forest to be amplified immensely.
Different media and genres use different levels of compression. Radio and television
commercials use compression to achieve a consistent wall of sound. If the radio or
television becomes too quiet, the audience may change the channel—a risk advertisers
and broadcasters don’t want to take. Films in theaters have a slightly wider dynamic range
because the ambient noise level of the theater is lower, so quiet sounds can remain quiet.
Stereo Audio
The human ear hears sounds in stereo, and the brain uses the subtle differences in sounds
entering the left and right ears to locate sounds in the environment. To re-create this
sonic experience, stereo recordings require two audio channels throughout the recording
and playback process. The microphones must be properly positioned to accurately capture
a stereo image, and speakers must also be spaced properly to re-create a stereo image
accurately.
If any part of the audio reproduction pathway eliminates one of the audio channels, the
stereo image will most likely be compromised. For example, if your playback system has
a CD player (two audio channels) connected to only one speaker, you will not hear the
intended stereo image.
Important: All stereo recordings require two channels, but two-channel recordings are
not necessarily stereo. For example, if you use a single-capsule microphone to record the
same signal on two tracks, you are not making a stereo recording.
Identifying Two-Channel Mono Recordings
When you are working with two-channel audio, it is important to be able to distinguish
between true stereo recordings and two tracks used to record two independent mono
channels. These are called dual mono recordings.
837 Chapter 52 Audio Fundamentals