How do I get good audio when filming video?

The built-in microphone on a camera or phone is at the wrong place by definition — it is where the camera is, not where the sound is. Every improvement in video audio follows from fixing that.

What you'll need

• A lapel or shotgun microphone, or a phone with wired earphones
• Headphones for monitoring
• A separate recorder or a phone as a backup recorder (optional)

Step by step

1. Get the microphone close.Sound pressure falls with distance, but room reflections do not, so the further the microphone is from the speaker the higher the proportion of echo in the recording. Thirty centimetres sounds present and clear; two metres sounds like a school hall.
2. Choose the microphone by the situation.A lapel microphone for interviews and pieces to camera, where it can be hidden and stays at a constant distance. A shotgun on a boom just out of frame for anything scripted, which sounds better still. A handheld microphone for street interviews. A camera-mounted shotgun only when nothing else is possible.
3. Treat the room before you blame the microphone.Hard floors, bare walls and glass produce reflections that no microphone rejects. Film in a room with a carpet, curtains and soft furniture, or hang a duvet out of frame behind the camera. This costs nothing and matters more than the microphone.
4. Set the level properly.Speak at your normal performance volume and set the gain so peaks land around minus twelve to minus six on the meter. Digital recording has no headroom above zero — anything that touches the top is clipped and permanently distorted.
5. Monitor with headphones.This is not optional. Handling noise, a rustling lapel microphone, a fridge compressor, traffic, wind and a cable fault are all inaudible while filming and obvious on playback. Headphones catch them while you can still do something.
6. Kill the room's own noise.Fridge, extractor, boiler, air conditioning, computer fan, phone notifications. Listen to the room with headphones before recording — you have been tuning these out all day and the microphone has not.
7. Deal with wind outdoors.A foam cover helps a little; a furry windshield helps enormously. Wind noise is low-frequency rumble that overloads the microphone, and it cannot be filtered out afterwards without hollowing the voice.
8. Record a backup.A second recorder or a phone running in the room is cheap insurance. Audio failures are silent until you sit down to edit, and a whole shoot with unusable sound is the most expensive mistake in video.
9. Record room tone.Thirty seconds of the space with nobody speaking and nothing moving. It is used in the edit to fill gaps and to smooth joins, and without it cuts between takes produce a noticeable change in background.
10. Sync separate audio deliberately.If you record sound separately, clap once at the start of every take in view of the camera. It gives a sharp spike and a visible frame to align to, which is what a clapperboard is for.

Tips

• Wired earphones with an inline microphone, clipped near the collar, are dramatically better than a camera microphone across a room, and cost almost nothing.
• Turn off automatic gain control if the device has it. It pumps the background noise up whenever nobody is speaking, which is very audible.
• Lapel microphones pick up clothing rustle. Tape the cable to the skin below the microphone and keep it clear of scarves, necklaces and zips.

Common mistakes

• Relying on the camera or phone microphone from a distance — It records the room as much as the voice, and no editing separates them convincingly. Distance is the single variable that decides how a recording sounds.
• Not listening on headphones while recording — Every audio problem is inaudible in the room and obvious on playback. By then the shoot has finished and the recording cannot be repeated.
• Recording hot to avoid a quiet track — Digital clipping is permanent and cannot be repaired. Record with headroom and raise the level afterwards, which costs nothing.

If it doesn't work

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