unvoiced vs voiceless

unvoiced

adj
  • Spoken without vibration of the vocal chords. 

  • Of an IRC user: not granted voice privileges. 

  • Not spoken or expressed. 

  • That does not contain voice. 

voiceless

adj
  • Spoken without vibration of the vocal cords; unvoiced, surd, breathed. Examples: [t], [s], [f], [m̥], [u̥]. 

  • Without a vote; having no input into a decision. 

  • Lacking a voice, without vocal sound. 

How often have the words unvoiced and voiceless occurred in a corpus of books? (source: Google Ngram Viewer )