In poetry, the auditory elements usually include sound devices which add rhythm to a poem and encourage a reader to interpret its mood and tone. In The Road Not Taken, Robert Frost wants the reader to find a personal message in the poem so he is attempting to illicit an emotional response which will prompt firm action or at least help the reader understand the contradictory effects of placing too much emphasis on a decision after it has been made and cannot be changed.
The rhyme scheme in the poem is consistent so that it creates expectancy and, for the narrator, a false sense of security. It is calming (abaab cdccd) and reassuring but belies the narrator's real feelings. The meter is a little more complicated and open to interpretation as Frost cleverly creates his own beat making the poem more unique and adding uncertainty- just as it should when there is a question of choice.
The use of repetition in the words "way leads on to way" and "ages and ages since" extends the length of time so that the reader can understand that the time frame is long and this is not some lightly-made decision. The repetition of the opening line also adds depth to the reader's understanding of the narrator's dilemma as the emphasis placed on how "two roads diverged" rather than the outcome of having taken one of the roads reveals just how much of a problem it is for the narrator to have to make a choice at all.
The use of sound devices or auditory elements therefore reinforces the message and reveals that there is a pattern in Frost's use of sound devices which support the theme and confirm the narrator's insecurities. He starts with what should be an interesting prospect. he introduces an interesting beat and then he lulls the narrator with the rhyme only to expose him for his inability to find satisfaction in his choice.