Production sound mixer, Erik H. Magnus, has posted to his website that he is working on The Whole truth starring Keanu Reeves and Renee Zellweger and he is now listed on the film’s IMDb page.
Mr. Magnus is based in New Orleans and he records dialogue for motion pictures and episodic television on location. He was nominated for the 50th annual 2013 CAS Award for Outstanding Achievement Sound Mixing in t Television Movie or Mini Series for Bonnie and Clyde Part Two.
Update: Here is a description of what a production sound mixer does from Get In Media.
The production sound mixer is the head of the sound department on set, and is brought in during pre-production to collaborate with the director and production manager to choose what type of microphones to use and select additional audio gear. This person may also give input on crew members to fill additional audio roles, like sound assistant, equipment technician, boom operator or cable runner.
During principal photography, the production sound mixer’s responsibilities are extensive. They include recording all sound on set: dialogue, sound effects, wild lines, live music, and room tone. He or she is also charged with maintaining log sheets for each roll of tape (or digitally formatted unit) recorded and marking printed takes, in conjunction with the camera assistant and script supervisor. The production sound mixer must make script notes to be used in case of reshooting (for continuity) and keep lists of wild tracks and sound effects that will be recorded later. This person will also direct the boom operator and design the placement of microphones and recording techniques for each shot—and keep an eye out for the dreaded boom shadow.