A measuring apparatus was developed; its probe tip, which exhibits flat frequency characteristics, enables this apparatus to measure the absolute sound pressure and absolute phase variations versus both sweeping frequency and external auditory canal pressure. Although it is difficult to diagnose ossicular chain separation and fixation from the commonly used tympanograms with a low probe tone frequency (e.g.f = 220 Hz), the results obtained with this apparatus enable one to clearly distinguish patients with ossicular chain disorders from normal subjects. Therefore, it seems to be highly useful in the clinical diagnosis of ossicular chain disorders.