The Collaborative International Dictionary of English v.0.48:
Aphonic \A*phon"ic\, Aphonous \Aph"o*nous\, a. Without voice; voiceless; nonvocal; incapable of all but whispered speech. [1913 Webster + WordNet 1.5]WordNet (r) 3.0 (2006):
aphonic adj 1: being without sound through injury or illness and thus incapable of all but whispered speech [syn: aphonic, voiceless]