Kapoor will be playing a partly deaf, partly mute man in the film, which is based on legendary comic actor Charlie Chaplin.
According to Mid-Day the actor will stop speaking from January and has already cut down the amount he communicates with people.
A close friend of the actor was reported as saying: "He wants to shut down all communication until he hears the sound of silence in his head."
Director Anurag Basu added that his latest project would be the funniest he has made, despite the tragic subject matter.
"Although Ranbir plays a physically challenged character, he is never depressed. This is a film about high spirits," he said.
"I love the mix of pathos and parody in Chaplin's performances. His silent films are a reference point for Ranbir. Chaplin could be hilarious even when he was placed in tragic situations."