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Abstract
Contractions of the middle ear muscles cause eardrum movements giving rise to pressure changes in the closed ear canal. The registration of these (extratympanic manometry) is strongly impeded by the presence of noise (mainly pulse). By application of extensive noise reducing constructions and repetitive oscilloscope tracings a greatly improved sensitivity has been obtained.
In a group of normal subjects a stapedius reflex has been recorded in both ears in all persons. The method is particularly suitable for latency determinations. The threshold of reflex by this procedure agrees with that obtained by the impedance method.
In some pathologic ears in which no reflex could be demonstrated by the impedance method the extratympanic phonometry has reveiled the presence of a reflex.