voicelessness vs speech defect

voicelessness and speech defect both are nouns.

Word	Noun	Adjective	Verb	Adverb
voicelessness	Yes	No	No	No
speech defect	Yes	No	No	No

As nouns, speech defect is a hypernym of voicelessness; that is, speech defect is a word with a broader meaning than voicelessness:

voicelessness: a disorder of the vocal organs that results in the loss of voice
speech defect: a disorder of oral speech

Other hypernyms of voicelessness include defect of speech, speech disorder.

voicelessness (noun)	speech defect (noun)
having no voice in the management or control of affairs	a disorder of oral speech
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