A silent film is a film with no synchronized recorded sound, especially with no spoken dialogue. In silent films for entertainment the dialogue is transmitted through muted gestures, mime and title cards.

Silent Film Sound:
Silent Film Sound (Book)
American silent film
Music and the Silent Film
Silent Films and Strange Stories: Theory of Mind, Gender, and Social Experiences in Middle Childhood
Fallen Women, Rising Stars, New Horizons: Shanghai Silent Film As Vernacular Modernism
Writing Himself into History: Oscar Micheaux, His Silent Films, and His Audience by Pearl Bowser; Louise Spence
New remission criteria for RA: 'modern times' in rheumatology--not a silent film, rather a 3D movie
Steven J. Ross, Working-Class Hollywood: Silent Film and the Shaping of Class in America. Princeton: Princeton University Press, 199...
Babel and Babylon: Spectatorship in American Silent Film. By Miriam Hansen. (Cambridge: Harvard University Press, 1991. xii + 377 pp...