Harry Potter and the Prisoner of Azkaban - Train Scene
The ice being formed on the glass window of the train would be an example synchronous sounds but the train tracks at 2:50 would be non-synchronous as you can not actually see the train moving along the tracks.
"Theres something moving out there" is a line spoken by the character Ron Weasley 0:59. This line is an example of functional dialogue however the large majority of dialogue in the scene is naturalistic.
A number of the sounds heard as the dementor enters the carriage the main characters are in could be considered hyper real. The rat's squeak was unnaturally loud, this was used to highlight the fact that even the animals were afraid of the creature too. Another example is the woman that can be heard screaming "Harry" its so distorted the transition from the scream to the steam engine sound is almost indistinguishable.
This scene uses both non-diegetic and diegetic music throughout to create two different effects.
The boggart scene consists of virtually all naturalistic dialogue. Professor Lupin explains to the class about the creature they're about to encounter. This would be exposition as the audience is learning just like the students.
The diegetic music in the scene is upbeat and lighthearted, this is because the character, Professor Lupin wanted to create a good mood for the students in the class.
The non-diegetic music on the other hand completely contrasts this. There is a glimpse of a dementor roaming the fields surrounding the castle just before we cut to the classroom. The music played is low pitched, and works as a sound bridge into the next scene (the classroom) but unlike the music used in the previous clip it lacks the fast paced string instruments as the characters are not in imminent danger. The first thing you see in the next scene is the cupboard, this is because Alfonso Cuaron wants to direct the audience's anxiety associated with the dementor onto the cupboard. The cupboard is violently shaking and something inside can be heard rattling inside which suggests that a dementor may also be inside trying to escape.
Unlike the music played previously, the non-diegetic music that begins at 2:13 initially starts out in a similar way to before but 10 seconds in high tempo string instruments start playing to represent neville's increasing heart rate. These string instruments could be considered to be a sound motif as the they are is very similar to the ones heard earlier so the viewer has learned to associate them with the dementors.
