Kira, I think you sprung a leak.

A little about wyvern vocalisations: While they can speak the languages of Men, these tongues are quite difficult for them, and often come out in a growling or gravelly tone. Sleet is better at it than most because he was raised speaking nothing BUT Falvaran (Falvaran is the dominant language in the world at this time; being the diplomatic language as well, most people learn to speak it). Wyverns hiss when showing aggression or trying to intimidate, but when in an attacking frenzy, they made shrill screeches or guttural cackles. The screeches are similar to eagle sounds, whereas the cackles can be likened to hyenas.