1 Corinthians 14:7-9

7And even things without life giving sound, whether pipe or harp, except they give a distinction in the sounds, how shall it be known what is piped or harped?1 8For if the trumpet shall give an uncertain sound, who shall prepare himself for battle? 9So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air.2