What characteristic identifies a Type Ad tympanogram?

A Type Ad tympanogram is characterized by a deep peak on the graph, which indicates high compliance of the middle ear system. This deep peak suggests that the tympanic membrane is able to move significantly, which can occur in cases of ossicular discontinuity or other pathologies that lead to an increased mobility of the ossicular chain.

This finding is clinically significant because it helps audiologists distinguish between normal ear anatomy and those abnormalities where the ossicles may be separated, leading to an increased transmission of sound through the middle ear. This peak is generally much higher than what would be observed in a normal (Type A) tympanogram, where the peak is less pronounced and indicates normal mobility.

In contrast, characteristics such as reduced tympanic membrane mobility indicate a Type B tympanogram, while normal ear canal volume corresponds to both Type A and Type B depending on other factors. High compliance is indeed relevant but is better associated as a defining feature of Type Ad rather than an independent characteristic.