Benefits from hearing aids in relation to the interaction between the user and the environment

It is becoming increasingly recognized that, in addition to the influence of audiometric variables and associated psychoacoustic abilities, the benefits from and candidature for various signal-processing schemes in hearing aids are strongly influenced by listeners' characteristics (such as motivations, expectations, and personality), and also the auditory environments in which those listeners are required to function (i.e. their auditory ecology). We will report elsewhere an experiment on a group of 50 listeners in a within-subject, randomized, blind, crossover design of five different hearing aid rationales, of which two contained linear amplification and three contained non-linear amplification which differed only in release-time constant. This article reports the interaction between the audiometric and cognitive characteristics of listeners, and the test conditions under which speech identification procedures are conducted (presentation level, signal-to-noise ratio, and temporal characteristics of interfering noise). The analyses show significant interactions between hearing impairment and cognitive ability, and the extent to which, when tested unaided, listeners can derive advantage from temporal structure in a background noise. The analysis then addresses the benefits of amplification (defined as the difference between performance in the amplified and unaided conditions) and shows significant interactions between cognitive ability, the temporal characteristics of interfering noise, and the time constants of non-linear amplification rationales. The direction of the interaction is that listeners with greater cognitive ability derive greater benefit from temporal structure in background noise when listening via fast time constants, one of whose effects is to facilitate 'listening in the gaps'.