Brief interview with Ben Burtt

pixar planet has a brief Q&A session with Ben Burtt, the sound designer on Wall-E.

In it he discusseshow he goes about creating voices for creatures and robots. He explains that voices are one of the hardest sounds to create as they have to be both intelligible and realistic for the creature/machine that's producing the sound. He finds that sounds that contain a human element and an electronic element work best.
He likens this to the creation of "ordinary" sounds for sci-fi films. He says that when you're trying to create the sound for a futuristic object that doesn't actually exist then it often pays to try and use a real-world sound as the basis as this will enable people to connect with the sound and make it more believable.