Speech and Hearing Sciences ETDs

Publication Date



Recent research has demonstrated that auditory learning can be adversely affected when performed under degraded listening conditions. Perhaps the most common of these degraded listening conditions are environments of moderate intensity noise, such as found in the class­room or in the home. A second degraded listening condition occurs when the speech signal is heard at a reduced intensity. This situation is experienced by the hearing impaired individual. That reduced speech intensity and/or noise can have detrimental effects upon learning has been almost exclusively attributed, by audiologists, to impaired signal intelligibility. The present study (which controlled for high speech intelligibility) investigated whether the added processing demands of auditory learning under degraded listening conditions could account for learning deficits. Specifically, the question examined was whether processing demands during auditory learning were greater under noisy versus quiet listening conditions and/or when the learning signal was presented at a reduced intensity level. To assess processing demands during auditory learning, a double stimulation procedure was employed. The double stimulation procedure allows the experimenter to simultaneously measure both processing accuracy (i.e., performance) and ease (i.e., attention or effort) during a learning task. In the present study, processing accuracy was determined using a paired associate learning task where 10 couplets of spondee words served as the learning stimuli. Processing ease was assessed with a probe reaction time task presented simultaneously during the learning task. The rationale for this procedure is that as the processing demands of the primary learning task increase, there will be a concomitant increase in reaction time during the secondary probe task. Forty-nine normal hearing undergraduates were randomly assigned to 7 experimental groups. Each of the groups heard the learning signal through the sound field under different listening conditions. These listening conditions represented the primary variables, and included: 1) Signal presented in quiet or noise (+6 dB S/N), and 2) Signal pre­sented at 50, 35, or 20 dB sensation level. Six of the experimental groups performed both the learning and probe reaction time tasks. The seventh group only performed the learning task, and thus served as a control condition. Results of the study indicated that neither of the primary variables exerted an effect upon learning accuracy. Rather, the results indicated a significant difference in learning ease between the noise and quiet listening conditions. Specifically, subjects in the noise conditions required greater effort to perform the learning task. No difference in learning ease was evident between groups at the different signal presentation levels. These results have important implications for: 1) The present listening conditions found in educational settings, 2) Hearing aid selection, 3) Education of the hearing impaired, and 4) Future audiological research and clinical procedures where multiple measures of auditory processing may be warranted.

Degree Name

Speech-Language Pathology

Level of Degree


Department Name

Speech and Hearing Sciences

First Committee Member (Chair)

Michael Allen Crum

Second Committee Member

Richard Baxter Hood

Third Committee Member

Max Edgar McClellan

Fourth Committee Member

Wayne Everett Swisher



Document Type