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Production3 min read

LESSON 112

Recording clean dialogue on set

Boom, lavalier, room tone.

IN THIS LESSON

  1. Who records it
  2. The boom
  3. Lavaliers
  4. Room tone
  5. Practice: a clean-sound checklist

Who records it

On a film set the production sound mixer, also called the location sound recordist, is responsible for every sound recorded during filming. That means choosing and placing microphones, choosing the recording media and mixing the microphones live. The mixer often scouts locations in advance for noise problems, brings wind protection for exteriors and records extra wild sound when asked. The recorded track is later combined with effects, music, narration, Foley and any re-recorded dialogue. Our earlier lesson on sound for video covered microphones and levels; this one is about the set.

The boom

The boom operator places a microphone on the end of a telescopic pole, usually aluminium or carbon fibre, and holds it as close to the actors as possible without letting the microphone or pole into the frame. The idea goes back to the first sound films: on Beggars of Life in 1928, director William Wellman is said to have hung a microphone on a broom handle to follow two walking actors, and on The Wild Party in 1929 Dorothy Arzner had one rigged on a fishing rod so Clara Bow could move freely. The operator also relays warnings about noises and upcoming shots back to the mixer.

Lavaliers

A lavalier, or lav, is a small microphone clipped to clothing, usually wired to a radio transmitter in a pocket or on a belt. Lapel microphones date from 1932. Many come with push-on grilles that gently lift high frequencies, which helps when the microphone sits on the chest or is hidden in the hair and loses some clarity. Lavaliers are quick and reliable for interviews and wide shots where a boom cannot get close, but clothing rustle is their main enemy.

Room tone

Room tone, also called presence, is a recording of a location's silence when nobody is speaking. Every room has its own, and it even changes with microphone position. Editors use it to fill gaps and smooth cuts in dialogue, because a soundtrack that suddenly goes dead sounds like a fault, not like quiet. The mixer records it in mono, with the microphone left where and how it was for the dialogue, and placed on the same track. Without it, the editor has nothing to lay under a cut where background noise changes between takes.

Practice: a clean-sound checklist

This is working practice. Turn off fridges, air conditioning and buzzing lights before takes, and leave a note on the fridge so it goes back on. Boom from above where possible and back it up with lavaliers. Record a minute of room tone at every location with everyone still. Listen on closed headphones throughout. Watch the levels so voices peak well below the top of the meter, and record a safety track a little lower in case someone shouts. Ask for one more take whenever a plane, a car or a cough lands on a line, and note the problem on the sound report so the editor knows which take is clean.

Try it today

  1. 01Record one line spoken by a friend with your camera's built-in mic.
  2. 02Record it again with a boom or handheld mic held just out of frame.
  3. 03Record it a third time with a lavalier on their collar.
  4. 04Record 60 seconds of room tone in the same room.
  5. 05Compare all three on headphones and use the tone to fill a gap.