Withheld information
Fear lives in the gap. A writer names the sound but not the source, so your imagination fills the space with something worse than any description.
Sentence length as heartbeat
Long, clause-heavy sentences build dread slowly. Then a short one lands. The rhythm change does as much work as the vocabulary.
Ordinary detail, wrong context
A kettle boiling in an empty house is unsettling because the detail is domestic. Horror often works by breaking normality rather than inventing something alien.