sound wave vs undulation

sound wave and undulation both are nouns.

Word	Noun	Adjective	Verb	Adverb
sound wave	Yes	No	No	No
undulation	Yes	No	No	No

As nouns, undulation is a hypernym of sound wave; that is, undulation is a word with a broader meaning than sound wave:

Other hypernyms of sound wave include wave.

sound wave (noun)	undulation (noun)
(acoustics) a wave that transmits sound	(physics) a movement up and down or back and forth
	wavelike motion; a gentle rising and falling in the manner of waves
	an undulating curve