Answer the following extract based questions :

i, And ere three shrill notes the pipe uttered,
You heard as if an army muttered;
And the muttering grew to a grumbling;
And the grumbling grew to a mighty rumbling;
a) Who owns the pipe mentioned in these lines ?
b) What figure of speech are the words 'grumbling', 'mumbling' and 'rumbling'?
c) Name the poem and the poet of the given lines.