The take was perfect for camera and cast, but a plane passed overhead in the last line. The production sound mixer asks for one more, while everyone is still in place. Re-recording that line in a studio later would cost a day of an actor's time and rarely sounds as natural. The production sound mixer is the head of sound on set and records everything the audience will hear the actors say.

What a production sound mixer does

The sound mixer works for the production and in practice for the director. They join in pre-production to visit locations and warn about noise problems, such as a busy road, an airport or a humming air conditioner, before a location is chosen.

On set they record each take on a portable recorder. They decide which microphones to use, usually a microphone on a pole held by the boom operator and small radio microphones hidden on the actors, and mix them as the take is happening. They write a sound report for every take and send the files to post-production, where the re-recording mixer uses them for the final mix.

Responsibilities

  • Check locations for noise problems before they are booked
  • Choose and set up microphones and recorders
  • Record and mix dialogue during every take
  • Work with the boom operator and the first assistant director on quiet on set
  • Record room tone (the silence of a space) and wild lines for the editor
  • Keep the timecode in sync with the cameras
  • Write sound reports and deliver the files to post-production

How the role touches the budget

Only a little. The sound mixer often brings their own kit and charges a rental for it on top of their rate. Extra radio microphones for a crowd scene or a second boom operator are small extra lines. Their biggest effect on the budget is invisible. Clean sound on set saves days of ADR (re-recording dialogue in a studio) in post-production.

How people become production sound mixers

Most mixers start as sound assistant or boom operator and learn the craft on set. Some come from music recording, radio or audio courses. Many own their recording kit, which makes the step to running a sound team a real investment.

In TV and documentary

On documentaries the sound recordist often works alone, holding the boom and mixing at the same time. In TV studios sound is mixed from a control room instead of a portable cart, and the title is usually sound supervisor.