The effects of air-bone gap and presentation level on word identification.

A sensorineural hearing loss is usually considered more disabling than a conductive loss of equivalent air conduction hearing level, due to the associated impairments in resolution which amplification does not overcome. In noise this generalization holds; however, in quiet, the generalization holds only for high intensity levels of presentation. Determination of isoperformance curves for word identification shows that at low stimulus levels the patient with conductive hearing loss suffers the greater disability for a given hearing loss. The crossover point between these regions, (i.e., where a single predictor from hearing level correctly predicts equal disability for conductives and sensorineurals) is in the region of 85 dB SPL--a level which approximates typical raised voice levels used when communicating under difficult circumstances. Given the long-standing distinction between conductive and sensorineural pathology, prediction of disability from dB HL as a general clinical substitute for actual disability measurement has rested upon a fortunate coincidence.