‘And the sound of the wings of the cherubim was heard even to the outer court, as the voice of God Almighty (El Shaddai) when he speaks.'
The sound of the wings of the cherubim was clearly also awesome (compare Ezekiel 1:24). It filled the whole house even to the outer court. And it was powerful and strong like the voice of the Almighty. In both cases the mention of the sound of their wings is connected with the actual voice of Yahweh being heard.