*Warning: Spoilers ahead*
If the sound of crackling ice were a language, it would be the White Walkers'. But, alas, the decision to take away the voice of the (growing) majority was made early on.
According to Vanity Fair, who recently combed through the Game of Thrones scripts that are on display at the Writers Guild of America West library, showrunners D.B. Weiss and David Benioff originally wrote the language into the show, but then it got scrapped.
In the show's pilot, the scripts say the Army of the Dead calls out in “inhuman shrieks” and “a chilling sound like crackling ice,” the same way George R.R. Martin’s books describe their native tongue. “These are not the noises of mindless predators. This is a language and whatever is speaking is getting closer,” the script reads. (*Shivers*)