Diegetic sound is the sound source visible on the screen or assumed to be present in the action of the film. The sound of a hound barking is the beginning as Sir Charles runs, and is used several other times in the film. The diegetic sound adds some eeriness to the film. This sound also helps people like Holmes and Watson come to the conclusion that there is indeed some kind of animal out there that may or may not be the killer. This sound is very important at the beginning of the film, because a bloodhound living on the moor is considered just a myth until Holmes investigates and comes to his conclusion.