Apple Final Cut Express HD - Manual (Page 586)

586 Part VIII Audio Mixing
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
We hear sounds in stereo, and our brains use the subtle differences in sounds entering
our left and right ears to locate sounds in our environment. To recreate this sonic
experience, stereo recordings require two microphones, two tracks of recording, and
two speakers for playback. The microphones and speakers must be properly positioned
to the left and right to accurately recreate a stereo image.
If any one of the above elements is missing, the stereo image will most likely be
compromised. For example, if your playback system has only one speaker, you will not
hear the intended stereo image, even if the rest of your recording system meets the
above requirements.
Important: All stereo recordings require two channels, but two-channel recordings are
not necessarily stereo. For example, if you only use one microphone but record that
signal on two tracks, you are not making a stereo recording. A proper stereo recording
must meet all of the above requirements.