clear as a bell vs discernible

clear as a bell

adj
  • Totally clear; distinct and unmistakeable, as a bell's tone is clearly heard. 

discernible

adj
  • Possible to discern; detectable or derivable by use of the senses or the intellect. 

How often have the words clear as a bell and discernible occurred in a corpus of books? (source: Google Ngram Viewer )