Tennyson wrote this poem out of his grief over the death of his friend Arthur Henry Hallam. He composed the poem over seventeen years, so their friendship must have been intense and his grief deep.
In section 28, it is Christmastime. Tennyson says that he awoke with pain that morning and almost wished he would never wake again, until he heard the Christmas bells and remember what day it was. Just as when he was a boy, Christmas brings him joy even in his sorrow. According to W. R. Nicoll in his book Alfred Tennyson: His Life and Works, the four "voices" of the four "hamlets" simply refers to the Lincolnshire villages around which he grew up.
As for literary devices, section 28 is composed in 5 stanzas, each with an ABBA rhyme scheme.
The last two lines of the third stanza are an allusion to the angels who visited the shepherds on the night of Christ's birth.
There is alliteration in the second stanza: "Four voices of four hamlets round,/ From far and near, on mead and moor"
The Christmas bells are personified as having voices that "dilate, and now decrease,/ Peace and goodwill, goodwill and peace,/ Peace and goodwill, to all mankind."
I hope this helps.