stage whisper vs susurration

stage whisper and susurration both are nouns.

Word	Noun	Adjective	Verb	Adverb
stage whisper	Yes	No	No	No
susurration	Yes	No	No	No

As nouns, susurration is a hypernym of stage whisper; that is, susurration is a word with a broader meaning than stage whisper:

stage whisper: a loud whisper that can be overheard; on the stage it is heard by the audience but it supposed to be inaudible to the rest of the cast
susurration: speaking softly without vibration of the vocal cords

Other hypernyms of stage whisper include voicelessness, whisper, whispering.

stage whisper (noun)	susurration (noun)
a loud whisper that can be overheard; on the stage it is heard by the audience but it supposed to be inaudible to the rest of the cast	speaking softly without vibration of the vocal cords
	the indistinct sound of people whispering