ask questions of vs sound out

ask questions of

sound out

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

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

  • To speak or sing loudly, to call out. 

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