Modification of nasal resonance in cleft-palate children by informative feedback.

Vibration of the walls of the nasal cavities during production of an English vowel or diphthong defined a hypernasal response. A crystal transducer on one side of the nose activated a voice-operated relay when vibration exceeded an arbitrary limit to provide an apparatus definition of the response. During training sessions, responses without nasal vibration turned on a white light in the sound-treated chamber. Subject 1 had a repaired cleft palate and mild hypernasal speech. Introduction of the differential feedback, reversal, and reinstatement of the feedback conditions resulted in a rapid decrease, increase, and decrease in percentage of nasalized productions of the /eI/ sound Subject 2 had a cleft of the soft palate and severe hypernasal speech. Introduction of feedback produced a gradual decline in the percentage of hypernasal productions of the /##/ sound over 22 sessions. Removal and reinstatement of feedback resulted in a rapid increase and decrease respectively in the percentage of nasalized responses.