Sound in practice — microphone selection, boom and synchronisation

An audience accepts surprisingly much varying image quality but reacts immediately to poor sound — noise echo or unclear speech makes the viewer turn off even when the image is beautiful. Therefore sound work on set is not a side task next to the camera; it is an independent discipline with its own equipment its own technique and its own pitfalls.

• 01Directional microphone (shotgun) on boom arm: captures dialogue closely and directionally without being visible in the image — the standard choice for dialogue scenes
• 02Make the template as the profile's negative, and file the edge clean
• 03Handheld microphone: typically used for interviews or reporting where the microphone itself is part of the picture

The boom operator holds the microphone as close to the speaker as possible without entering the frame, and angles it towards the mouth rather than directly from above where the sound would otherwise be hollow and distant. This requires the boom operator to know the frame's crop precisely and continuously adjust the rod's angle and distance as people in the scene move.

Microphones are typically connected with an XLR cable, which sends a balanced signal — this means the cable can be run a long distance without picking up noise, unlike a standard unbalanced jack cable. Most professional condenser microphones also require 48-volt phantom power from the mixer or recorder to function at all, so it is a fixed part of equipment checking to confirm that phantom power is turned on before recording begins.

If audio is recorded on a separate audio recorder instead of directly in the camera — which provides better quality and flexibility — image and audio must be synchronized in editing afterwards. This is solved either with a clapper board where the visual and audible 'clap' provides a common reference point for both tracks, or with timecode where the camera and audio recorder are locked to the same timecode so the editing software can synchronize automatically.

• 01Clapperboard: simple, inexpensive solution that requires manual synchronization in editing
• 02Timecode synchronization: requires equipment that supports it but saves time with many clips and long shoot days

Before the crew leaves a location, the sound technician should record 30 to 60 seconds of silence at the location — called room tone. It sounds like nothing, but is used in editing to fill gaps, cover cuts, and smooth transitions, so pauses in dialogue don't sound like technical silence but as a natural part of the room's sound.

Outdoor recording adds a challenge that does not exist in a studio: wind. Even a light breeze can create a deep, rumbling noise on the recording that is difficult or impossible to remove completely later in editing. Therefore, a windscreen or a dedicated 'dead cat' wind shield is almost always used on the microphone outdoors, and on very windy days it may be necessary to move the recording to a sheltered location or postpone it if the sound would otherwise be unusable.

The best equipment cannot save a sound technician who is not listening actively along the way. Headphones over the ears during the entire recording is not a formality — it is the only way to detect a humming rig a creaky floorboard or a plane in the distance before the recording is in the can and the error is only discovered in the edit room. A rule of thumb is that if what the headphones tell the sound technician doesn't appeal to them the scene should be retaken — regardless of how good the picture looks.