coup de glotte
n.— «Actually, Mr. Johnson explained, the trick at the heart of ventriloquism isn’t “throwing” the voice but “treating” it. Thanks to a throat-muscle manipulation that opera singers call a coup de glotte, the amplitude of the emerging sound waves is constricted in a way that the human ear misinterprets as distance. Keeping the lips immobile and shifting focus supports the illusion.» —“Broadway for Dummies (and Ventriloquists)” by Jesse Green New York Times Sept. 17, 2006. (source: Double-Tongued Dictionary)