Clear/sound as a bell

For centuries, one of the clearest sounds was that of church bells, which could be heard from miles away. Thus, clear as a bell means perfectly clear but oddly appears to be not as old as sound as a bell which means perfectly healthy or perfectly trustworthy. As sound as a bell dates from the mid-1500s and was used but not coined by Shakespeare in Much Ado About Nothing (1598-1600) Act III, Scene II, “He hath a heart as sound as a bell.” As clear as a bell dates from about a century later.