What physical details of time and place accomplish the mood and what is the effect of using the word soundless to describe the day in "The Fall of the House of Usher"?
The long opening sentence immediately establishes a mood for the story.
Poe's Gothic tale of dualities is rife with ominous happenings, decay, darkness, and foreboding. The use of alliteration with /d/ in the opening sentence--"dull, dark, and soundless day"--generates a dismal mood and an atmosphere of gloom. This mood is also accomplished with certain words and phrases relating to time and place. For instance, the mention of autumn, a season marking the end of colorful foliage and flowers, suggests death; the "dreary tract of land" on which the narrator rides furthers the mood of gloom, as do the "shades of evening" which fall upon the "melancholy House of Usher."
The word soundless in reference to the autumn day clearly connotes lifelessness. Usually in autumn there are still birds singing, squirrels scampering about in the fallen leaves, and, perhaps, even a rabbit hopping somewhere. And, so it is that the narrator states that as he approaches the House of Usher," a sense of insufferable gloom pervade[s] [his] spirit." It is interesting to note, also, that as a counterpoint to the Romantics' use of the sublime, a powerful experience that overwhelms human emotion and perception, Poe creates a dull, lifeless, and soundless scene that is completely devoid of this quality of the sublime as the atmosphere is barren of any uplifting beauty and energy.