The spell say:
Your form transmutes into living ice, granting you several abilities. You gain the cold subtype and damage reduction 5/magic. You are immune to ability score damage, blindness, critical hits, deafness, disease, drowning, electricity, poison, stunning, and all spells or attacks that affect your physiology or respiration, because you have no physiology or respiration while this spell is in effect. You cannot drink (and thus can't use potions) or play wind instruments.
It don't say "you can't speak", but the no breathing part seem to imply that.
So the question is:
You can speak?
The implications of the answer are very important for spellcasters.
As written I would say that the subject of the spell can't speak, use breath weapons and so on, but it is a implied thing.