clear as a bell vs observable

clear as a bell

adj

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

observable

adj

  • Able to be observed. 

  • Deserving to be observed; worth regarding; remarkable. 

noun

  • Any physical property that can be observed and measured directly and not derived from other properties 

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