Obscure auditory dysfunction (OAD) is a disorder characterized by patient report of excessive amounts of difficulty understanding speech in the presence of background noise, despite relatively normal hearing sensitivity. It has been hypothesized that OAD may be the result of mild cochlear dysfunction, central auditory processing deficits, and/or psychological disorders. To evaluate auditory processing aspects of this disorder, speech recognition was measured in complex listening conditions for 10 normal-hearing persons with self-reported problems understanding speech in noisy environments. Ten normal-hearing listeners without reported difficulty hearing speech in noise served as controls. Each participant completed a standard audiometric evaluation, the QuickSIN test (standard clinical test of speech recognition in noise), and experimental speech recognition measures in simulated background environments, which included a range and combination of competitor stimuli presented in monaural and binaural conditions. The results show that the OAD participants had poorer overall speech recognition abilities in noise than did control participants for the experimental speech recognition tasks. The pattern of performance deficits suggests that the speech-understanding problems of these OAD participants are not attributable to abnormally poor binaural hearing or to a reduction in masking release. Further, performance deficits exhibited by listeners with OAD were not identified by a standard clinical speech-in-noise measure.

Military noise environments, and, in particular, the noise environments faced by dismounted soldiers on the battlefield, are characterized by wide variations in ambient level. Situations can quickly and unexpectedly change from quiet conditions where the sound of a snapping twig might alert the listener to hostile enemy activity to extreme noise conditions where firefights, explosions, or loud machinery create levels of noise that can cause hearing loss in a matter of minutes or seconds. This poses a unique challenge for the designers of military hearing protection, who must produce systems that provide enough comfort and acoustic transparency to convince users to consistently wear them in quiet conditions to ensure that they will be in place if an unexpected blast or other potentially damaging noise exposure occurs. In this talk, we discuss some of the issues that can influence the willingness of listeners to wear hearing protection for extended periods in quiet environments, including acoustic factors that have been shown to influence situational awareness while wearing hearing protection. Additionally, lessons on the factors impacting the comfort of hearing devices drawn from studies of how consistently hearing aids are worn by hearing impaired listeners will be discussed.