There are no shortage of haunting images in “Us,” the new horror film from Jordan Peele. But many of the movie’s most effective jolts are heard rather than seen, from the chilling score (including a macabre riff on Luniz’s “I Got 5 on It”) on down.

No sound in the film is more likely to induce nightmares than the voice of its main villain, Red. Played by Lupita Nyong’o in a dual performance (she is also Adelaide, Red’s non-villainous doppelgänger), Red becomes the movie’s most unsettling enigma the moment she first opens her mouth.

(Warning: If you haven’t seen “Us,” moderate spoilers about the character follow).

In a showstopping monologue at the top of the second act, Red’s speaking voice — a dyspeptic rasp, as if her vocal cords have been gnawed through by rats — suggests someone who has seen the unspeakable, and takes an already eerie performance by Nyong’o to a darker, unearthly realm.

[Read the review of “Us,” and watch how Jordan Peele builds suspense in the film.]

The sound has provoked strong reactions in audiences and critics. In his review, New York magazine’s David Edelstein described it as “the whistle of someone whose throat has been cut” and “a rush of acrid air from a tomb.”