The audio part of a video program is usually built up from several different sound tracks. These individual components can vary considerably in both their level of reality and their function in the overall sound track.


Level of Reality

Some sounds are absolutely authentic, some are completely artificial, and some fall in between these two extremes. Listed in order of reality, we find:

Live sound.  This audio is recorded simultaneously with the video and is often called the production track.   Live sound includes spoken dialogue, the noises created by the action, and the ambient sounds of the shooting location.

Sweetened sound. This is live audio that has been processed in postproduction to improve its quality.  In some cases, a process called equalization strengthens certain sound frequencies (pitches) while relatively weakening others. Often, extra live sound is added to conceal the audio differences between different shots.

Foley sound. This is a track of sound effects recorded live in a special studio while the video is displayed, so that Foley technicians can synchronize the sounds they are creating with the program in real time.  For example, a Foley studio may have several sections of floor covered variously with gravel, asphalt, concrete, or tile, for use in recording footsteps sounds effect synchronized with the footfalls on on-screen actors walking on similar material.

Library sound.  This is audio that is not created specifically for a particular program, but is stored on discs for use where needed.  Some sound libraries contain thousands of different effects.  General back ground sounds such as waves or forest noises, or city traffic are often recorded on digital “loops”.

Synthesized sound.  This is a digital audio that is created on a computer instead of being recorded acoustically.

Audio functions.

Audio tracks can also be classified by their functions.  Here are some of the most common uses for sound:

Production sound.  As noted above, this s is sound that is recorded with the video.

Presence.  Often called room tone, presence is recorded at a shooting location while the cast and crew remain perfectly still.  The result is a recording of the location’s faint background sounds, such as ventilation systems or equipment hum.  Presence is used to fill gaps in the production track left when unwanted sounds are cut out.

Background sound.  This is an ongoing sound effect like the chatter of diners and the tinkle of china and silver in a restaurant.  When the background track is mixed with the live production tracks, shot-to-shot changes in sound quality are smoothed over.  Like presence, background sound smoothes out differences in the production track.  But it is als  intended to supply sound that was not present during production recording.

Sound effects. Sound effects (often abbreviated “SFX”) are specific sounds such as walk, gunfire, or car engines that are added in post production, whether from Foley recording or from a sound effect library.

Dialogue replacement.  This is a process by which actors re-record dialogues in a studio, synchronizing it to the lip movements of performers as played back on a monitor or screen.  The procedure is still often called “looping” because in pre-digital days it was accomplished by splicing the film containing a few lines of dialogue into an endless, head-to-tail loop, which could be projected continuously.

Music.  Music is added to the sound rack to enhance continuity and communicate feeling.  Music composed for a specific program may be timed right down to the frame.  Library music (pre-composed and stored selections ) may be selected by length, or else faded in, faded out, or both, in order to time it to the picture.  Digital music loops contain embedded information that allows them to be adjusted precisely to fin any length required.

Excerpted with permission from Video: Digital Communication & Production Second Edition by Jim Stinson Copyright 2008. You can read an overview of this new textbook elsewhere in this issue of School Video News. Get more information on this and other valuable textbooks from Goodheart-Willcox by clicking here.