1 Corinthians 14:9

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

The same is true of speaking to the church. Unless members speak in easily understandable speech, how will others know what they are saying? How will they know what to do? Their words will vanish into thin air, which will absorb them unheard (because not understood). Only the fresh air will hear them, just as the uncertain notes of the trumpet disappear into the air 'unheard'.

However, it must be seen as possible that by 'you will be speaking into the air' Paul wishes them to have in mind 'the air' in which spirits were seen to exist. Ephesians 2:2 speaks of 'the prince of the power ('power' there was the equivalent of 'kingdom' - compare 'power of darkness' (Colossians 1:13)) of the air'. In this case he would be reminding them of his words in 1 Corinthians 12:1. (This may have been more obvious to them than to us if 'the air' was generally recognised as a sphere of spirits). He may be saying that publicly spoken tongues are only of interest to the spirit world, and without love may well be an indication of the interest of false spirits. However, few commentators see it that way. If it does have that in mind the thought is not expanded on.