Henry Wadsworth Longfellow's "The Sound of the Sea" is in the form of an Italian or Petrachan sonnet.
The meter of the poem is regular iambic pentameter, with very few variations.
The rhyme scheme of the poem is a Petrachan or Italian sonnet, a form first imported from Italy to Britain in the Renaissance and know after the poet Petrarch, its most important Italian practitioner.
The form consists of 14 lines, divided into an octave followed by a sestet with a "volta" or turn between the two, meaning some sort of change of tone or subject matter.
The octave consists of two open quatrains (abba, abba). The sestet consists of six lines using two or three rhyme sounds arranged in any order. Longfellow's sonnet uses cdecde for its sestet.