or pots on the audio console; 100 percent modulation or 0 db is read on the VU meter. Sound levels are
what is heard, but signal levels are what is actually being recorded or going through the equipment.
(1) With the use of audio equipment, a correct level is established when the signal peaks at
zero db or the 100 percent modulation point on the VU meter. Any continuous modulation which goes
over zero db or 100 percent modulation mark is called "over modulation" or "riding in the mud." The
end result of over modulation is distortion, because the signal amplitude is too high for the equipment to
(2) Just as over modulation produces distortion, under modulation or "riding in the mud",
will produce a low volume and a low signal-to-noise ratio. Because both over modulation and under
modulation are undesirable situations, they should and can be avoided by "riding the gain." Riding the
gain is the process of constantly readjusting the signal levels during a recording to maintain a proper
(3) Occasional peaking into the red area of the VU meter, because of abrupt changes in
volume level in music selections or emphasis in voice tones, are acceptable as long as they do not
happen too often. When levels must be changed during a recording, the changes should be done
gradually so they are unnoticed. This may present a real challenge when using a musical selection
which has many abrupt changes in levels as do marches or some classical presentations.
b. Balance. Balance is the difference in sound loudness between two or more sound sources. It
is dependent on the audio engineer's hearing and aesthetic sense or balance (how the various sound
sources sound together). Studio speakers must all be the same volume of loudness to achieve a true
balance. A good example of this is the use of music under an announcer's voice. The audio engineer
must determine if the music is too loud and drowning out the announcer's voice or if the music is too
low and cannot be heard.
(1) An ear for balance is something which most audio people develop after working in the
field for awhile. In determining the balance of various sound levels a variety of things can be done.
These may vary from just increasing or decreasing the signal gain on a particular source to moving a
microphone closer to a speaker.
(2) The balance of many sounds should be done prior to recording. Balance is achieved
mostly through testing and trials.
c. Operating Techniques. Operating techniques refers only to the technical aspect of audio
mixing and good techniques depend upon how well the operator handles the equipment and how well he
mixes or blends his sources. The operating techniques should be smooth so that any changes made will
be unnoticed by the listener. Some of the terms used to describe basic operating techniques are: fading,
crossfade, segue, down and under, and up and under.