You don't? I think he's already got it subconsciously:

And in the Most Ancient Hall of the Wizengamot an icy voice rang out, speech the color of liquid nitrogen, pitched too high for that it came from too young a throat, and that voice said, "Lucius Malfoy."

seemed a pretty clear reference to

Then the other voice spoke, high-pitched like the hiss of a teakettle, and it was like dry ice laid on Harry's every nerve, like a brand of metal cooled to liquid helium temperatures and laid on every part of him.