From The Regnum Animale by Bishop Vitellus of Oaken:
There are few living who can claim a thorough knowledge of the lilting, rhyming language of the Fey. It is clear that this tongue can be conveyed through all manner of sounds, from clicks and buzzes to whistles and hoots to spoken words as we understand them. This causes me to speculate that intent may be more important than vocalization when speaking Sylvan, which of course renders any academic study of the language vain. What is clear is that while we may not understand Faeries when they deign to speak, they clearly understand our words.