Lactantius

“ For the voice is not produced outside of the mouth, but within, and therefore that opinion is more probable, that the breath, being compressed, when it has struck against the obstacle presented by the throat, forces out the sound of the voice: as when we send down the breath into an open hemlock stalk, having applied it to the lips, and the breath, reverberating from the hollow of the stalk, and rolled back from the bottom, while it returns [2] to that descending through meeting with itself, striving for an outlet, produces a sound ”