This poem describes a train as if it were a horse. which lines uses imagery to describe sound of a train?

The sound imageries are found in the first line of last stanza  the words "neigh" and "Boanerges."  

Explanation:

This poem called "I Like to See it Lap The Miles" was written by Emily Dickinson.  It's a four stanza poem where a train is compared to a horse. There's mostly visual imagery. The train passes on valleys and mountains, stops for fuel and it goes downhill. In the last stanza, however, we can find two words that describe the sound that the train makes:  "neigh" and "Boanerges". "Neigh" is the loud sound made by a horse. "Boanerges" is a vociferous ( i.e loud and forceful) preacher. These two words help to convey  the loud powerful noise a train makes when blowing the horn. It's making a stop like a horse stops at a stable.