Use of the articulation index for assessing residual auditory function in listeners with sensorineural hearing impairment.

Two experiments were performed to explore the feasibility of deriving an articulation index (AI) based scheme for quantifying residual auditory function in listeners with sensorineural hearing impairment. In the first experiment the AI procedure was applied to audiograms of normal and sensorineural hearing-impaired individuals in order to predict speech discrimination under various conditions. Good predictions were found for the normal and the less impaired subjects, but not for those with greater impairments. These subjects exhibited a disproportionate loss in speech discrimination compared to that predicted on the basis of the AI procedure. In the second experiment it was investigated whether the AI predictions for presbycusic individuals could be improved by making use of the proficiency factor that is not a function of frequency. The results indicate that the deficit in suprathreshold speech processing is frequency-specific and that, therefore, the proficiency factor is not independent of frequency. It assumes the value of 1 at those frequencies where hearing sensitivity is normal and is substantially reduced for frequencies where hearing threshold is elevated.