examples of sense of sound in birches

The senses are pretty vivid in this poem. It is as if Frost has given a voice to New England's natural elements. 

You'd think the inner dome of heaven had fallen.
They are dragged to the withered bracken by the load,
And they seem not to break;

When the narrator looks at the birch trees in the forest, he imagines that the arching bends in their branches are the result of a boy “swinging” on them. He hears the sqeaks and laughter of swinking from trees in his childhood. He realizes that the bends are actually caused by ice storms - the weight of the ice on the branches forces them to bend toward the ground.