Boom mics record the actor's voices, which are then edited during audio post production.

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Different Aspects of Audio Post Production

In film and TV, the audio portion of a project is recorded separately from the video. Unlike your home video camera, the film or video cameras used in professional productions don't have built-in microphones. Instead, all dialogue is recorded with either a boom microphone (those long sticks with the fuzzy mics on top) or a tiny, wireless lavalier mic that can be hidden in an actor's clothing. Most other audio -- like ambient background noise and music -- is added in post production.

Post production refers to all the editing, assembling and finalizing of a project once all the scenes have been shot. Audio post production begins once the editors have assembled a locked cut of the project. A locked cut of a film contains all of the visual elements -- selected takes, special effects, transitions, graphics -- that'll appear in a film's final cut.

With the locked cut in hand, the audio post-production staff can start spotting the film for sound. Different members of the post production team look for different things:

  • The dialogue editor examines every line of spoken dialogue, listening for badly recorded lines (too quiet, too loud, jarbled, et cetera) or times when an actor's voice is out of sync with his lips.
  • Sound effects designers look for places where they'll need to add ambient background noise (honking cars in a city, tweeting birds in the country), and "hard effects" like explosions, doors slamming and gun shots [source: FilmSound.org].
  • Foley artists look for places to fill in details like footsteps across a wood floor, a faucet running, the sound of a plastic cup being placed on a marble countertop, et cetera.
  • The music editor looks for inspiration to either commission original music or buy licenses for existing song use.
  • The composer, if he's already hired, looks for places where original music would add to the on-screen moment.

If the dialogue editor needs to replace or re-record unusable pieces of dialogue, he'll ask the actors to come in for an automated dialogue replacement (ADR) session. Here, the actors and editors synchronize the newly recorded dialogue with the lip movements on the screen and mix the audio smoothly into the existing recording.

Foley artists -- named after the pioneering audio and effects man Jack Foley -- use an eclectic bag of tricks to reproduce common sounds (a wooden chair for a creaky floor, cellophane for a crackling fire, a pile of audio tape for a field of grass, et cetera) [source: The Art of Foley].

Sound designers and effects editors spend much of their time collecting libraries of ambient natural sounds. They record the sound of Monday morning traffic and save it as a digital file for later use. They record washing machines running, children playing and crowds cheering. You can also buy ready-made libraries with all of these sounds. But some of the best sound designers like to create entirely original effects.

Ben Burtt, sound effects designer on the original Star Wars movies, used a distorted elephant bellow for the roar of a tie fighter. And the famous hum of the lightsaber? A blend of TV static and a 35mm projector [source: FilmSound.org].

The most important job in audio post production is the mix, where all of the sound elements of a project are balanced and blended together. Typically, this job is shared by a dialogue mixer, effects mixer and a music mixer [source: FilmSound.org]. The final copy of the composite soundtrack is delivered either on optical film stock, as a digital file or both.

Now let's look at some of the systems and software used in audio post production.