"Life of Pi" is an adventure film directed by Ang Lee. Adventure films often do well in sound categories at the Oscars, including last year's winner "Hugo."
"Zero Dark Thirty" is an action film about the killing of Osama bin Laden. It's directed by Kathryn Bigelow, whose previous film, "The Hurt Locker," won both sound Oscars in 2009.
"Skyfall" is the latest film in the James Bond franchise. Big-budget action films are often nominated for sound awards, but no Bond film has won since "Goldfinger" won Sound Editing in 1964.
"Django Unchained" is a western directed by Quentin Tarantino, whose last film, "Inglourious Basterds," was nominated for both sound awards in 2009.