Simultaneous recording of changes in relative impedance and air pressure during acoustic and non—acoustic elicitation of the middle—ear reflexes

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Abstract
Intra—aural reflex responses for normal and pathological human ears were obtained while utilizing equipment constructed at Sahlgren's Hospital. Acoustic and tactile stimuli were employed to elicit reflexes. Responses were displayed simultaneously on two channels of a graphic recorder, indicating changes in amplitude and amplitude—phase of an 800 Hz probe tone in the recorded ear. Changes in air pressure in the same sealed auditory canal in response to middle—ear muscle contraction were simultaneously recorded on a third channel. The response pattern on the impedance indicator and on the pressure transducer system during acoustic stimulation are primarily due to the stapedial muscle reflex. In a small fraction of the group of normal subjects (13 %) it appears that contraction of both middle—ear muscles was elicited by acoustic stimulation. In the group in which the tensor muscle was the only functioning muscle in the middle ear, the tensor reflex could not be elicited by acoustic stimulation.