Location sound starter: boom, lav, room tone

By James Jones, founder of Granary Digital · Updated 5 November 2026

Location sound has one job: get dialogue that the editor can use. A boom microphone close to the mouth does most of it. A lavalier covers what the boom cannot reach. Thirty to sixty seconds of room tone fills the gaps the edit will open. Get those three right and most of the repair work never happens.

You can add atmosphere, music and effects later. You cannot take noise out of dialogue without damaging the voice, so every minute spent on the set improves what comes after.

Listen to the room first

Before you rig anything, walk the location with headphones and a notebook. Stand where the actors will stand and listen for a full minute. Write down everything you hear:

• Fridges, freezers, air conditioning and extractor fans
• Traffic, aircraft and building work
• Clocks, creaking floors and radiators
• Buzzing from lights, dimmers and chargers
• Phones, laptops and notifications

Then deal with them. Switch off what you can, move what you can't, and ask permission before you unplug a fridge. Put a note on the door of it so somebody plugs it back in. Hard, bare rooms echo, so soft furnishings, curtains and blankets help. If a noise cannot be dealt with, tell the director before you roll, so the decision is theirs.

The boom

A boom is a directional microphone, often called a shotgun, on a pole, held just out of frame. It sits in a suspension mount with a windshield around it. Directional microphones pick up most from the front, so you aim them at the mouth.

Where it goes. Hold it above the speaker pointing down at the mouth. Overhead is usually cleaner because it points away from floor noise and footsteps. If a low ceiling or a lighting rig stops you, hold it below frame pointing up instead.

How close. As close as the frame allows. Halving the distance lifts the voice by about 6 dB against the room, so a boom 30 to 60 centimetres from the mouth sounds far cleaner than one at a metre and a half. Check the frame with the camera operator, using the monitor, and move the mic in until you can just see it, then back out a little.

How to hold it. Overhead work is tiring, so rest the pole on your shoulder or a stand between takes. Rehearse the movement with the actors, and follow the person who is talking, not the person who is moving. Keep your fingers off the pole in the shot, because handling noise travels down it. Watch for the boom's shadow on a wall or an actor's face and ask the lighting crew to help if it shows.

Safety. Carbon fibre poles conduct electricity. Keep them away from lights, wiring and overhead power lines. This is general guidance, and a competent person must assess the actual site. The page on what a boom operator does describes the role in more detail.

The lav

A lavalier is a small microphone clipped or taped to the speaker's chest, usually on a wireless transmitter. Use it when the boom cannot get close: wide shots, moving actors, crowded sets or a noisy room.

It is small, so placement decides how it sounds:

• Position: on the breastbone or just inside the collar, a few fingers below the chin, with the capsule facing up and out.
• Clothing: synthetics, silk and stiff cotton rustle. Tape the cable and the mic so fabric cannot rub across the capsule. The lav placement guide shows where each position works.
• People: warn the costume and make-up departments before you dress the actors, because they decide where a transmitter pack can sit.
• Batteries and radio: change batteries between set-ups and check there is no interference before you roll.

A lav sounds close and dry whatever the shot size, while the boom sounds like the room the audience can see. Record both on separate tracks. The editor can then use the boom for the natural sound and the lav when a take needs rescuing.

Levels and settings

• Sample rate and bit depth: 48 kHz and 24-bit is the usual starting point for picture work. Set every recorder and the camera to the same sample rate.
• Headroom: a sensible starting point is dialogue peaking around minus 12 dBFS. At 24-bit that leaves enough quiet level to be clean, with room for a surprise.
• Set the gain on the loudest line. Ask the actors for a rehearsal at performance volume, because a whisper and a shout need different settings. If the meter touches the top, the sound is damaged for good.
• Separate tracks: record each microphone on its own track. A mixed track alone gives the editor nothing to fix.
• Monitoring: wear closed-back headphones for the whole shoot and listen to what is recorded, not just the live feed. A meter will not tell you about a hum. Your ears will.
• Camera audio: record a scratch track on the camera, so the editor can sync the sound from the recorder.

The timecode and sync explainer covers how the picture and sound line up, and a sound report template gives you the paper log for each take.

Room tone

Room tone is the sound of the location when nobody is speaking. Every room has its own, and a dialogue edit needs it. When the editor removes a cough, tightens a pause or cuts between two takes, the gap has to sound like that room or the cut jumps out.

To record it:

1. Ask the first assistant director to call "room tone" once the scene is shot.
2. Everyone stops where they are, and nobody speaks or moves. Phones stay silent.
3. Record 30 to 60 seconds on the same microphones and with the same settings as the scene.
4. Keep the set exactly as it was: lights, doors, fridges and air conditioning all in the same state.
5. Say the location and scene number on the recorder and write the file on the sound report.

Record a new one at each location and after anything that changes the sound, such as lights on or off, a door opened or a window shut. Also record a few "wild" lines, which are lines spoken without the camera running, if a take had noise on an important word.

Common problems and quick fixes

A checklist before you roll

1. Listen to the room and deal with the noise.
2. Check every battery.
3. Set sample rate and bit depth the same on every recorder.
4. Set the gain on the loudest line.
5. Monitor on headphones.
6. Slate each take, with the scene and take number.
7. Record room tone at the end of the scene.
8. Fill in the sound report.

If you can book a studio

Recording in a studio takes much of the noise list at the top of this page out of your hands: traffic and weather matter far less indoors. You still need room tone, and you still need to listen. If you are adding a sound recordist, Granary lists one from £495 +VAT a day, indicative, and our kit includes Sanken COS-11D lavalier microphones. You can book the room through studio hire, and the sound and post-production page covers the work that follows.

Related guides

• Lav placement: where to clip a lavalier microphone
• Sound report template, with a worked example
• Timecode and sync explained, with an LTC test file
• Audio test pack: tones, pink noise and sweeps
• How does remote ADR work?
• All guides and tools

The picture at the top of this page is an illustration, not a photograph of a client or a real job.