Modern Times, the last of Charlie Chaplin's films to star his famous "Little Tramp" character, was released in 1936 as a comedic commentary on the effects of the Great Depression. Chaplin felt strongly that the rising implementation of industrial processes were directly responsible for the high unemployment rates of the time and he expressed these views satirically throughout the picture. In what might have been another attempt to take a jab at modern technology, Chaplin decided to forgo any real talking in the film even though talking pictures had already been in continuous production since 1927. He also felt that the silent pantomime style of comedy that made his "Tramp" character so famous should remain intact for the character's final film appearance. The only human voices to be heard during the film are when they are being emitted from various technological devices (such as a phonograph), in some sound effects, and when Chaplin momentarily sings in faux-Italian babble in one of the movie's final scenes.
Source: Robinson, D. (2004). Filming Modern Times. Retrieved from: https://www.charliechaplin.com/en/articles/6-Filming-Modern-Times