[1] Esophageal speech uses air supply to create phonation from the esophagus and pharyngo-esophageal segment to act as a replacement for the glottis.
[2] This is created by producing an air bubble between the left (or right) upper jaw and the cheek that can act as an alternative "lung".
The person then uses muscular action to drive the air through a small gap between or behind the teeth into the mouth.
This produced an “unpleasant, markedly hoarse voice quality which was consistently evident in her pharyngeal speech".
[1] Such speech was "generally well understood by immediate family members" but "reported to be largely unintelligible to outsiders".