Even things without life that give sound, whether pipe or harp, except they give a distinction of sounds, how shall it be known what is piped or harped? For if the trumpet give an uncertain sound, who shall prepare himself to the battle? So likewise you, except you utter by the tongue plain speech, how shall it be known what is said? For you shall be speaking into the air.

1 Corinthians 14:7-9 (as quoted in Catholic Bible Douay-Rehims) - First Epistle to the Corinthians