The proposed research comprises four areas of investigation. The objective of the first project is to produce a homogeneous subset of passages of connected discourse that are equivalent in intelligibility as assessed either by a method-of-adjustment or a rating procedure. Equivalence will be established separately on normal-hearing listeners and listeners with sensorineural hearing loss. The final product will be a Revised Speech Intelligibility Rating (SIR) Test. In the second project we will examine the functional relation between frequency and intelligibility by defining the frequency-importance function for connected discourse and comparing those results with previously reported findings for other measures of speech recognition. In the third project we will describe the ways in which intelligibility is transferred among different measures of speech recognition. The final project will concern the differential effects of spectro-temporal characteristics of maskers on the intelligibility of connected discourse, and endeavor to distinguish between the masking and distracting effects of competing signals (maskers).
