He explained the effects of sounds on the senses. Everyday sounds are what tell us where we are. The disjointed, short, cacophonic sounds of the city have no rhythm and so you feel restless. Sounds outside the city are quieter, stretched longer, and hence more peaceful. The job of a sound designer is to create an invisible environment, the one we can't see, but which adds to our understanding of where the protagonists are.
Once Open runs the story I will post it here. In the meantime, a brief explanation of what he does, in his own words, from the interview:
"Any sound in a film is not accidental. It is there for a particular feeling, to add texture. In a film if we use 400 tracks of sound, it means we've listened to more than a million files of sound. Not just once. It's far more tedious work than a composer's. When you write a characterization in film, I'm doing the same thing with sound. In sound, if its not real, the audience will reject it. Unless it's a larger-than-life movie. Ghajini was [that kind of movie], and the objective was that the audience shouldn't move from their seat. At the same time, Ghajini had a great emotional line. So I could be as violent as I could. But we decided to restrict ourselves. It's all about killing the girl, right, how brutally you can kill her to create sympathy. We could create brutal sounds. But the audience is a family audience, so if you're brutal, they'll be like "ew". So what we did is, one minute into the film, we brought in metal sounds. You hear soft metal sounds. Every sound we created was metallic. You hear a multitude of metallic sounds. Then we bring the sounds back in reel no.9, where the police inspector narrates the story of how she was killed. So on reel no.1, we started working on the audience's mind with metal sounds, and then we slapped it. The audience accepted it. For me it was a great artistic decision."
This was a brief excerpt; the actual interview is longer and more detailed. It was fun. There's nothing like interviewing a person who loves what he does, and shows you how he does it. Also, I couldn't take my eyes off his magnificent digital recoder. I wanted to go to there.