1 Corinthians 14:7-11

7Even things without life, giving a voice, whether pipe or harp, if they give not a distinction in the sounds, how shall it be known what is piped or harped?

8For if the trumpet give an uncertain voice, who shall prepare himself for war?

9So also ye, unless ye utter by the tongue speech easy to be understood, how shall it be known what is spoken? for ye will be speaking into the air.

10There are, it may be, so many kinds of voices in the world, and no kind is without signification.

11If then I know not the meaning of the voice, I shall be to him that speaketh a barbarian, and he that speaketh will be a barbarian unto me.