sound structure vs word structure

sound structure and word structure both are nouns.

Word	Noun	Adjective	Verb	Adverb
sound structure	Yes	No	No	No
word structure	Yes	No	No	No

As nouns, sound structure and word structure are synonyms defined as:

sound structure and word structure: the admissible arrangement of sounds in words

Other synonyms of sound structure include morphology, syllable structure.

sound structure (noun)	word structure (noun)
the admissible arrangement of sounds in words	the admissible arrangement of sounds in words