Since various types of tympanograms (T. G.) are obtained in the cases of otitis media with effusion (OME), it may be rather difficult to determine the actual pathophysiological states of the middle ear cleft by mean of impedance audiometry.
In this paper, we attempted to investigate how various types of T. G. are formed by experimentally modified middle ear clefts. The plastic models, the guinea pigs' middle ear bulla and the human temporal bone which is obtained at the time of autopsy, are used in the present experiments. The results; 1) B type of T. G. is often produced by an occlusion of the aditus-equivalent-site of the plastic models and of the epitympanic isthmus of the human temporal bone. 2) Even if the middle ear effussion is present in the mesotympanum, B type of T. G. is not detected in the plastic ear models, guinea pig and human middle ear specimens without blockage of the aditus-equivalent-site. 3) A blockage of the aditus as well as a diminution of the capacity-volume of the mastoid cavity are chief causatives of the pathological types of T. G. 4) The present experiments could not draw any conclusions about a question how does a viscosity of the effusion affect to the form of T. T. G. 5) Middle ear pressure is almost equivalent to the pressure at the peak of the compliance.
