There are many different types of sound that are extremely important, if not more so than the visual aspects of a film. Dialogue, music and sound effects are the three types of sound used within film. Dialogue is used for obviously speaking, when a character talks his or hers voice will be heard and that contributes to the visuals at the same time. Sound effects are also very important, when a character is walking you will be able to hear the sound of someone, not always them walking. If someone slams a door, you will hear this. If sound effects were not placed into a film you would never get the same effect. Music is something that plays during the film that references what is going on, Its not something the characters are saying or doing as it tends to add to the film’s mood/emotion.
Very often sound within a film is not the sound that would have been there while recording/filming was happening. The sounds would have been added during the editing process and would have been made by sound artists.
For example, sound is used during the shower scene of Alfred Hitchcock’s psycho, the character can be seen taking a shower, sound effects are evident as the viewer see’s a dark shadow approaching the shower curtain. Screams are exploded from the character and more sound effects while the victim is being brutally stabbed. These sound effects make the scene more horrific/realistic.