What are some literary devices in Robert Frost's "The Sound of Trees"?

Robert Frost's "The Sound of Trees" employs a first person speaker to meditate on the relationship between humans and trees.
The speaker begins with a rhetorical question:

I wonder about the trees.
Why do we wish to bear
Forever the noise of these
More than another noise
So close to our dwelling place? (1-5)

The speaker "wonder[s]" why people choose to live in such close company to trees. He asks why we choose to hear the "noise of these / More than another noise." Some of the word choice has a slight negative connotation: "to bear" and "the noise," for example. These phrases suggest that humans "put up with" the sounds that come from trees, as though there is not something inherently pleasant or peaceful about them. The entire poem, as we can see from these first few lines, is written in free verse, with no set rhyme scheme or stanza structure. The lines also feature enjambment, where the speaker's thoughts flow from one line to the next, usually without punctuation at the end of every line. This style more effectively mirrors the speaker's meandering thought process than a more structured form would do.

The speaker continues the ideas first established in lines 2-5 in the following several lines:


We suffer them by the day
Till we lose all measure of pace,
And fixity in our joys,
And acquire a listening air. (6-9)



The word "suffer" is another example of significant diction with a negative connotation. He describes the effect of the trees on the speaker and other humans, however, in a less negative way when he says they "acquire a listening air" from previously "los[ing] all measure of pace."

Next, the speaker writes,


They are that that talks of going
But never gets away;
And that talks no less for knowing,
As it grows wiser and older,
That now it means to stay. (10-14)



The unusual repetition of the word "that" in line ten makes the reader pause and read carefully. The trees represent "that that talks of going / But never gets away." The trees are stable and permanent, and they are also personified when the speaker describes them as "wiser" and ascribes intention to them ("it means to stay.").

The final section of the poem shifts focus back on to the speaker, as he writes,

My feet tug at the floor
And my head sways to my shoulder
Sometimes when I watch trees sway,
From the window or the door.
I shall set forth for somewhere,
I shall make the reckless choice
Some day when they are in voice
And tossing so as to scare
The white clouds over them on.
I shall have less to say,
But I shall be gone. (15-25)

Here, the imagery conveys the similarity between the speaker and the tree. The speaker feels more firmly planted, like a tree, and moves like a tree sways in the wind. Further, the speaker echoes the previous notion about trees in lines ten and eleven when he says, "I shall set forth for somewhere / I shall make the reckless choice." This indicates that the speaker sits there fixed but thinks of moving on and going elsewhere. He also juxtaposes the previous description of trees as "wiser" with his own perception of himself as having the capacity for "reckless[ness]." The speaker ends the poem with an image of the trees in the future, "tossing so as to scare / The white clouds over them on." The difference is that the speaker will be dead, and he will no longer be there to hear the trees' "voice[s]," as he is now. The speaker ends with a reflection on the permanence of the trees versus his own mortality.