Tympanograms of weighted models. An experimental study.

We examined tympanometry using an ear drum model made of plastic tube and film of polychloride vinyliden. Weights of plastic rubber (30mg to 150mg) were placed on the center of the film. As more weights were added, the tympanogram (probe tone÷220Hz) showe dhigher peaks. When a weight of about 180mg was placed on the membrane, the tympanogram developed into a two-peak type.Similar results were obtained in clinical cases. When a metalic weight of about 93mg was attached to the umbo of the tympanic membrane, in some cases the tympanogram showed higher peaks than when there was no load, and in other cases it developed into a multi-peak type.Our study revealed that when a weight is placed on the film, the type of tympanogram can be changed, for example from A to M. Therefore, when a weight, such as metal or fluid, is attached to the membrane, the tympanogram may show higher peaks than with no load. The same weight was placed on the film in different places and with varying areas of contact. Tympanograms showed the highest peaks when a weight covered a small area at the center of the membrane.These results indicate that, in humans, the ossicular chain may act to increase the peak of the tympanogram. However, the area of the malleus in contact with the ear drum may be regarded as relatively large when the highest peak of the tympanogram is relatively small.We added a pars flaccida model, and the results suggest that the pars flaccida influences the type of tympanogram at lower frequencies.