Christopher Nolan says the way Heath Ledger modulates his Joker voice, “from its highest pitch to its lowest pitch, is very extreme, and where it shifts is unpredictable and sudden” (via The Hollywood Reporter). He also remarks that Ledger’s line delivery was “always a surprise” (via Gothamist). The actor composes a symphony with his voice, rising and falling at any given moment with a sinister blend of malice and charisma, all tied together with his trademark laugh. He suddenly moves from high-pitched, childlike sounds to bellowing anger.
There are chilling moments where he utters “I’m not crazy” in a quiet, even-keeled whisper, or bellows “LOOK AT ME!” in his kidnapping video. This sudden roar, (which was downright terrifying in IMAX) comes out of nowhere, indicating that he is always just one step away from unhinged anger. All it takes is a little push. These erratic vocals keep both the characters and the audience on edge, never knowing exactly how he is going to respond or if they’ll be the next victim in one of his menacing games.
His loud, gravelly voice is also very exaggerated and performative. Nothing he says sounds sincere, especially the story about his scars. Using interweaving levels and intonations, the Joker paints himself as the commanding, ostentatious ringleader of a twisted circus, torturing the citizens of Gotham for his own amusement. The Joker’s vocals are both scary and impressive, truly capturing the deranged absurdity of someone who just wants to watch the world burn.