The relationship between the visual and aural in film has been at work since its inception.  Sound, which in the loosest sense of the term refers to any auditory accompaniment to the images on the screen-this could include dialogue, sound effects, music, and the like- impacts and influences the parameters of the cinematic experience.  The puropse of this article will be to include a brief history of how sound in film originated, with special regard to the implications of the radical introduction of commercially-viable "sound films" (which refers to the synchronization of the film's audio with the film itself). 

History

Although "sound films" were not widespread until the 1920's, the pairing of audio with image dates back to early cinema.  Thomas Edison was involved in some of the earliest attempts to marry sound with film, which resulted in what Walter Murch calls "officially the oldest synchronous film in existence" (filmsound),the Dickson Experimental Sound Film, which was produced in 1894.  Kinetoscopes were being produced by 1913 that were fitted with special phonographs that provided a rudimentary synchronization with the images. In this particlular setup, "synchronization was achieved by connecting the projector at one end of the theater and the phonograph at the other end with a long pulley" (filmsound).  These marriages of sound and film were far from perfect, however, and often suffered from a lack of accuracy in matching the audio to film. It should be noted that, throughout this early period in cinema, films in theatres were often accompanied by audio in the form of musical score, whether from record or live production.

It was not until the wide-spread incorporation of the "sound-on-film" technique- meaning that the audio track is recorded onto photographic film, most often the same strip of film as the images- that films featuring dialogue and diegetic sound became mainstream (sound films caught on especially quickly in the United States).  1927's The Jazz Singer is often credited as the first film with truly synchronized diaglogue sequences (wikipedia).

Implications of Sound

The effect of sound, especially that of spoken dialogue, had a radical impact on the spaces and realities that film could explore.  In the case of Jean Renior's film La Grande Illusion, for example, character identity is explored through the use of different spoken languages.  If the film relied entirely on inter-title cards or subtitles, as silent film did by way of necessity, the impact of language on character becomes somewhat flattened, as the subtitles themselves were inevitably in the language that was most effective and comfortable for the viewer.  In Renoir's film, national identity and class are explored and indicated by the characters' use of language.  While the French soldiers invariably speak French, and the German soldiers largely speak German, the interaction between the two is central to the film's efficacy.  In one scene, the cordial politeness of the Germans is demonstrated when one of them addresses a captive French soldier in his native tongue. 

*there is much to be done in terms of major editing to this page. Namely, someone could address the exchange between the two officers in English, and any other important uses of sound beyond dialogue in the film.

"History of Film Sound." FilmSound.org: dedicated to the Art of Film Sound Design & Film Sound Theory. 30 Sept. 2009

Sheenan, James. "Jean Renoir's "La Grande Illusion"" American Historical Association. 23 June 2008. 30 Sept. 2009.

"Sound-on-film." Wikipedia. 30 Sept. 2009.