In the poem, the techniques that are being used are Repetition and Onomatopoeia.
Repetition is a poetic device in which the same word, phrase, or stanza is being repeated over the poem. It is used by the author to emphasize the words in the poem more for the audience.
Onomatopoeia is a poetic device in which the sound of a word imitates its sense. The author uses this device for the the better understanding of words and to portray an imaginary picture of those words in the minds of the readers.
The words :"it" keeps repeating so we came to know about the repetition and hence words like whistles, thunders it out the sense of the word so we know it onomatopoeia.
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