question vs sound out

question

verb
  • To ask a question or questions; inquire or seek to know; examine. 

  • To ask questions of; to interrogate; to ask for information. 

  • To raise doubts about; have doubts about. 

noun
  • A subject or topic for consideration or investigation. 

  • A sentence, phrase or word which asks for information, reply or response; an interrogative. 

  • A proposal to a meeting as a topic for deliberation. 

  • A doubt or challenge about the truth, accuracy, or validity of a matter. 

sound out

verb
  • To question and listen attentively in order to discover a person's opinion, intent, or preference, especially by using indirect conversational remarks. 

  • To pronounce a word or phrase by articulating each of its letters or syllables slowly in sequence. 

  • To speak or sing loudly, to call out. 

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