Sound is important because it is one of the main things you will pay attention to when watching a Trailer.
Different Volumes will be used to make the audience anxious and jumpy.
Distorted sounds can be used to make the audience feel uneasy.
Innocent sounds (Such as a young girls voice) can be used to lure the audience into a false sense of security as this is not something usually matched with the horror genre.
Thudding music can be used to match the human heartbeat. Due to this, if you speed it up, the audience will think their heartbeat is increasing.
