Pixar's much-awaited movie about WALL-E, a robot who gets left behind on an abandoned Earth, opened to rave reviews this weekend, despite the fact that there is almost no dialogue in the first half of the movie. Instead, the audience is treated to special sound effects created by four-time academy award winning sound designer, Ben Burtt.

Ben, whose previous work includes the Star Wars series and many of the Indiana Jones movies, says he is no stranger to special sound effects. However, even he concedes that WALL-E was one of his most challenging movies. While most of the other movies had between 700-1000 sound files, WALL-E needed 2,500 sound files. While he succeeded in making the sounds amazing on screen, a behind the scenes glimpse of how he recorded some of the sounds is even more fascinating.

When Ben needed some shopping cart noises for a funny scene, he and his 10-year old daughter placed a recorder wrapped in bread inside a real Safeway cart. They then tossed it against items in the parking lot to get the most authentic sound effects. After that, they let the cart roll down a long hill, recording the entire trip, until its crash at the bottom.

In order to get the right 'whirring' sound that WALL-E makes in the movie, Ben used a World War 11 hand-cranked generator that he purchased from auction company Ebay. When WALL-E moves faster in the movie, the sound effect is created by an inertia engine starter used for biplanes in the 1930's.

His biggest challenge in the movie however was creating the voice for WALL-E and his friend EVE. In the end, they were created similar to how R2D2's voice in the Star War's series was created - by electronically altering a human recording.

While sound effects are important in any movie, in a movie like WALL-E, where there is little dialogue, it is the only thing that can keep the audience engaged - and judging by the early success of the movie, it seem like Ben Burtt has once again outdone himself.

SFgate.com