“Hearing” in the Bible means more than just the collection of atmospheric vibrations: It represents receiving and understanding new ideas, particularly those from the Lord. On a deeper level it represents obedience, because we must understand to obey. This also is reflected in natural language, in which we often use “hear” to mean “obey.” There are many shades of meaning beyond that, depending on context -- who is hearing whom, and what the subject at hand is.