Location Sound

What is location sound?

Location sound is the audio a film records at the moment of shooting, as opposed to sound created later in post. It sits at the start of the whole chain of sound in film: what the set captures is what editors cut, clean up and mix.

The team is small. The production sound mixer runs the recorder, sets levels and decides which microphones cover each shot. The boom operator holds the pole and follows every speaker just outside the frame line. On bigger shoots a sound utility (second assistant) wires actors, manages batteries and cables and handles a second boom.

What they record:

• Dialogue — the main job, as clean and close as the frame allows.
• Room tone — 30 to 60 seconds of the location's own quiet, recorded with the whole crew frozen.
• Wild lines — the actor repeating a line off camera, in the same space, when a take was spoiled by noise.
• Wild tracks — ambiences and specific sounds of the place (a door, an elevator, a café) for the sound editors.

The word sync matters. Film cameras record picture only, so feature films have traditionally captured sound on a separate recorder (double-system recording) and lined up later — originally with the clap of a clapperboard, today mostly with timecode.

Why production sound matters

A performance is a single event: breath, pace, overlap, the way a voice changes when an actor turns away. Production dialogue keeps all of that. Lines re-recorded weeks later in a booth can match the lips and still lose the moment, which is why most directors fight to keep the set track.

Filmmakers who built their style on the set track prove the point. Robert Altman's Nashville (1975) put radio microphones on a large ensemble and recorded them on separate tracks, so overlapping conversations could be balanced in the mix instead of staged one line at a time. Les Misérables (2012) recorded its singing live on set rather than miming to a playback, trading control for immediacy. And Singin' in the Rain (1952) turns the early talkies' struggle with hidden microphones into comedy, a reminder of how much staging once bent around the mic.

There is also plain economics of time: every scene saved on set is a scene that doesn't need an ADR session, an actor's schedule, a stage and a dialogue editor's hours to hide the seam.

How to record sound on set

Boom first. A boomed microphone above the actor, pointed at the mouth and kept 30 to 60 cm away, gives the most natural dialogue because it hears the voice and a little of the room together. Outdoors, a shotgun reaches farther and rejects the sides; indoors, a hypercardioid usually sounds cleaner, because a long shotgun in a small room picks up hard reflections.

Lavs as backup or primary. A lavalier microphone hidden in costume covers wide shots, walk-and-talks and scenes where a boom can't reach. Most mixers record lavs and boom on separate tracks and let the dialogue editor choose.

Levels and format. Record at 48 kHz, 24-bit or 32-bit float, with dialogue peaking roughly between -20 and -10 dBFS and headroom left for shouts. Keep a separate iso track for every microphone plus a mixed track sent to camera as a reference.

Sync. Jam-sync timecode from the recorder to every camera at call time and re-check after lunch; still slate each take so the editor has a visual check.

Control the set. Before the first take, hunt noise: refrigerators, air conditioning, buzzing ballasts, squeaky floors, hard shoes. Put wind protection on every exterior mic. Talk to the DP early: a wide and a close-up shot at the same time forces the boom to the wide frame line, and hard backlight throws boom shadows onto walls.

Audio recording in production: what the files contain

When people say audio on a production, they usually mean the recorded sound files and the discipline of capturing them cleanly. A typical day's delivery from the sound department contains:

• Polyphonic WAV files (Broadcast WAV) — one file per take, with every iso track and the mix track inside, stamped with timecode, scene and take metadata.
• Sound reports — a sheet per roll listing each take, which track holds which actor, circled takes and problems (plane, truck, clothing rustle).
• Room tone and wild tracks — labeled by scene so editors can find them.
• A backup — most recorders write to two cards at once.

Good metadata is half the job: an editor who can see that track 3 is the lead's lav and take 4 has a car horn saves hours in the sound mix.

Location sound vs. ADR

Both deliver dialogue, but at different moments and with different strengths.

• Location sound is captured during the scene, in the real space, with the full performance. It carries natural acoustics and energy but also every noise that was there.
• ADR is re-recorded later in a studio, in sync with picture. It is clean and controllable, but has to be made to sound like the location with matching mics, reverb and background.

The usual workflow treats ADR as the fallback. When a take is noisy, the mixer asks for a wild line on the spot; only what can't be saved on set or by cleanup goes onto the ADR list.

Planning sound before the shoot

Most sound problems are decided at the location scout: a flight path, a highway, a school playground at 3 p.m., an echoing concrete room. Bring the sound mixer on the scout and ask them to listen for a few minutes in each space.

In FlashBoards, keep the scout photos for each location on the board next to the storyboard frames for that scene, with notes about noise sources and times of day, which shots need lavs and where the boom can stand. When the shot list changes, the sound team sees which setups became wide or cross-shot and can plan for it before the call sheet goes out.

Further reading

Tomlinson Holman, Sound for Film and Television (Focal Press) · Ric Viers, The Location Sound Bible (Michael Wiese Productions)