Anatomy and physiology

The audition of cleft child does not work in a normal way. The most common reason of a disfunctioning ear is Otitis Media with Effusion (OME). Conduction loss is the prodominantly hearing loss of OME. A feature of conduction loss is the reduced intensity of the oscillation that normally reach the eardrum. This causes by ignition of OME in the middle ear. The ignition will be mute, what results in poorer perception in the inner ear. 
Another physiological deviation is the Eustachian tube. Because of the abnormal anatomy of the palate and the muscles, the Eustachian tube does not open normal. With every swallow the tube will open, by children with a cleft the tube opens insufficient. When the child get a palate operation the tube will function, most of the time, better. So there will be more oscillation that reaches the eardrum.