Phonation in oesophageal speech in a case of laryngectomy is produced by:

In a normal person phonation is produced by vocal cords which vibrate in response of force of air produced by lungs. In oesophageal speech, patient "inhales" air into the oesophagus and then ejects it by the contraction of chest muscles. Pharyngo-oesophageal segment functions for the missing vocal cords and vibrates to produce phonation. Since only limited amount of air can be ejected from the oesophagus, maximum phonatorv time is short and patient can speak only a few words.