The poem arouses an eerie feeling in us as we read it. How does the poet achieve this?

The constant knocking builds a sense of uneasy suspense:

Is there anybody there?" said the Traveller, Knocking on the moonlit door"

"And he smote upon the door a second time, "Is there anybody there?" he said."

"For he suddenly smote on the door, even Louder, and lifted his head:-"

The constant knocking of the Traveller disrupts the silence and loneliness of the poem as he desperately tries to call to some unknown person or person within the house.