Non-diegetic sound
Sound that has been added- which characters cannot hear such as voice-over or music
Parallel sound
Sounds that complements the actions onscreen
Asynchronous sound
Sound which contradicts or conflicts with the actions onscreen
Voice-over
A person who talks over the images, usually narrating or contributing to the story.
Soundtrack
Music or songs that creates mood and atmosphere to the visuals
Diegetic sound
Sound which characters can hear such as speech or an explosion.