How does the poetic element of sound develop the theme of "Mending Wall"? I have to focus on the aspect of sound and how it develops the poem's theme.
To discuss sound here, let us separate three kinds – the ambient sound, of the atmosphere, the physical place (wind, animal sounds, clanging of stones, footsteps, etc.) -- the sound of dialogue – discussions, human spoken words – and the poetic sounds – rhythm, rhyme, scansion, repetition, etc.
The most obvious ambient sound is “the yelping dogs.” Subtler sounds are the “frozen ground swell,” the clanging of stones (both as they hit the ground when falling and the sound of their being replaced), and perhaps the footsteps of the poet and the neighbor. The dialogue sounds are of two kinds: the actual conversation ("Good fences make good neighbors") and the imagined or implied or unspoken dialogue ('Stay where you are until our backs are turned!'; 'Why do they make good neighbors? Isn't it/ Where there are cows?” This implied dialogue, while not spoken in the scenario, is sounded out in the reader’s mind when reading the poem . Finally, there is the gentle rhythm of the poetic lines themselves – the carefully constructed scansion and beat lengths (“That sends the frozen-ground-swell under it” ; “We wear our fingers rough with handling them.”), and the very subtle rhymes ( made repair/ we find them there). Frost has constructed a legitimate narrative of the event, but has given his descriptive lines a natural yet poetic flow that enhances the whimsical, friendly observations of the narrator. The sound of the poem is personal and philosophical, giving weight to his theme : we should examine our habits.