It refers to the sound crew member responsible for the process of recording all sync dialog and sync sound effects in a scene. He is the head of the sound department on the set. His duties are: selection and operation of the microphones, and recording equipment used on the set, directing the boom operator, combining the sound of multiple microphones used to capture dialog and effects on a set, recording sound ambiance and room tone for all scenes, and wild track that will aid the editor and sound mixer in matching the different sound takes in a scene for smooth sound transitions.