Answer:
first-person narrative voice
Explanation:
The author, in his work, may opt for one of possible narration ways.
Third person is usually most common way. The author narrates and explains actions, thoughts and emotions of several (or all) characters.
However, Frost in this poem only describes the way he feels after a crow shook down some snow from a tree directly on him. He is the only character (well, besides the crow) and all that we, as readers, or audience, know, are his thoughts and emotions. That means that he narrates from his own perspective, and that is the feature of the first person narration.
