ABSTRACT
This chapter reviews the role of audibility in speech perception by the hearing impaired before considering the role of suprathreshold factors, particularly the use of computer simulations to evaluate the importance of suprathreshold factors. It describes a series of studies designed to assess the importance of suprathreshold factors for speech intelligibility by simulation of their effects, either singly or in combination. People with cochlear hearing loss have difficulty understanding speech in quiet situations when the speech is at low sound pressure levels, as well as in the presence of background sounds, even when the speech and noise levels are relatively high. The intelligibility of speech in noise was adversely affected by the smearing, especially for large degrees of smearing and at low speech-to-noise ratios. The signal-to-background ratio required to achieve a given level of intelligibility is plotted relative to the value for normal hearing. The smearing had adverse effects on speech intelligibility, especially at adverse speech-to-background ratios.
