voicelessness vs aphonia

voicelessness and aphonia both are nouns.

Word	Noun	Adjective	Verb	Adverb
voicelessness	Yes	No	No	No
aphonia	Yes	No	No	No

As nouns, voicelessness and aphonia are synonyms defined as:

voicelessness and aphonia: a disorder of the vocal organs that results in the loss of voice

voicelessness (noun)	aphonia (noun)
having no voice in the management or control of affairs	a disorder of the vocal organs that results in the loss of voice
speaking softly without vibration of the vocal cords
(phonetics, of a consonant) The property of being spoken without vibration of the vocal cords, as [t], [s], or [f].
a disorder of the vocal organs that results in the loss of voice