This passage is important to the novel as a whole in the way that it features the perennial conflict that Jane faces during the course of the story, but from one side, namely, her cousin, St. John. We can see in the text you have quoted that St. John is busy trying to pressurise Jane to marry him and go with him to India to workk there as a missionary. In the novel as a whole, it is vital to realise that St. John symbolises the forces of duty and reason. He wants Jane to marry him, not because he loves her romantically, but so she can be his helpmate in India. The force of St. John's personality is so strong that Jane feels herself succumbing to his proposition in spite of her desire to marry for love:
I was tempted to cease struggling with him--to rush down the torrent of his will into the gulf of his existence, and there lose my own.
However, what saves Jane is the dream she has of hearing Rochester's voice crying out for her, which gives her the strength she needs to assert herself and defy his hold on her life. Note the way that Jane describes this sudden coming to life of her spirit:
It was my time to assume ascendancy. My powers were in play, and in force.
This passage is therefore important as it captures one element of the ongoing conflict that Jane faces as she struggles to strike a balance between sacrificing her life on the altar of duty and reason on the one hand, and then giving it over completely to passion and feeling on the other.
Which literary devices used in this passage? Would it be correct if we say "Pathetic fallacy" as she used the wind as a symbol?
`What have you heard? What do you see?` asked St John. I saw nothing, but I heard a voice somewhere cry- `Jane! Jane! Jane! - nothing more. `O God! what is it!` I gasped. I might have said, `Where is it?` for it did not seem in the room, nor in the house, nor in the garden; it did not come out of the air, nor from under the earth, nor from overhead.
"The wind sighed low in the firs: all was moorland lonelines and midnight hush".