The show's sound designer, Paula Fairfield, spoke with WNYC's Radiolab to discuss the inspiration behind the dragons' voices, speaking specifically about Drogon, the dragon that is perhaps closest to the Lady of Dragonstone.
"I have sounds I might choose simply by certain personality traits that I want to push forward," Fairfield said. "So in the case of Drogon, she named that dragon after Khal Drogo, her hot, late husband, and so Drogon is like her lover. He's whistling at her all the time, he's looking at her butt and going, 'ooh baby.' "
Most often, the noises are composites of various creatures in the animal kingdom, including birds, insects, and different kinds of amphibians, but in the case of Drogon, the sound inspiration comes from a less family-friendly source.
"Two giant tortoises mating. The groan of the male actually became, with some work and adjustments, the source for Drogon's purr with her [Daenerys]," Fairfield continued. "The funny thing about the purr with Drogon was watching people watching [the show] and giggling when they heard it, but not really knowing why. To me, it's because it had that essence, that kind of sensual, sexual essence."
While mating giant tortoises may be the main source for Drogon's "voice," Fairfield also said that she drew inspiration from dragonfly wings to create the sound of Drogon's thorns on the end of his tail as he moves.
For fans hoping for Khal Drogo's return, they're going to have to settle for the sensual relationship between the Mother of Dragons and her mating tortoise-sounding dragon Drogon. Jason Mamoa squashed rumors that he'd be making an appearance in the show's eighth and final season.
Game of Thrones season 8 is expected to premiere in 2019.