The Stenger Principle describes the observation that when two tones of the same frequency are presented simultaneously, a single tone is perceived only in the ear in which the tone is louder. This principle underlies the Stenger Test, which is used to identify the presence of unilateral nonorganic hearing loss (NOHL). Minimum contralateral interference levels (MCILs), which can be used to estimate true hearing thresholds in individuals with unilateral NOHL, are also based on this principle. In this study, the Stenger Principle is used to examine MCILs and the correspondence of the MCILs to true hearing thresholds in 16 adults with normal hearing. In Part I of the study, subjects were asked to feign a unilateral hearing loss. Average MCILs were 12.5, 15.1, and 13.5 dB HL for 1.0, 2.0, and 4.0 kHz, respectively. These were obtained with nearly equal interaural stimulus levels. The average difference between MCIL and true hearing threshold was 7.6, 9.7, and 8.9 dB, respectively. In Part II of this study, subjects were asked to make lateralization judgments for simultaneously presented tones with varying interaural intensity differences. Individual subject ratings were compared to MCILs obtained in Part I. Although most subjects showed the Stenger Effect with a midline percept of the two tones, variability between subjects existed. In some cases the Stenger Effect was not apparent until the tonal image was pulled nearly to the "poor" ear. Because of the potential differences in response bias (a client may show the Stenger Effect with a small shift in the tonal signal away from the "good" ear or may require the tonal signal to be fully lateralized to the "poor" ear), clinicians cannot predict exact hearing thresholds. Rather, it is useful to describe a range within which the true threshold will be. The 90% ranges (5th and 95th percentiles) calculated in this study were approximately 1 and 17 dB. That is, the MCILs for the majority of the subjects were within ~ 1 and 17 dB of true hearing thresholds.

No description available.

The Auditory Steady State Response (ASSR) procedure has been established as a frequency specific, objective audiologic measure, which can provide reliable thresholds to within 10 dB of the behavioral thresholds. In order for ASSR to find its place in the existing framework of audiometric procedures, the full potential of the procedure needs to be explored. The aim of this study was to determine the accuracy of monotic ASSR in estimating hearing thresholds in a group of 15 normal hearing subjects and 15 hearing-impaired subjects. A comparative research design was implemented. Indicating that results obtained in the study was compared to relevant literature where dichotic multiple ASSR was implemented. This was done in order to ascertain ASSR’s capabilities with regard to stimulus presentation methods. Monotic single ASSR predicted behavioural thresholds in the normal hearing subjects within an average of 24 dB across the frequency range (0.5, 1, 2&4 kHz). In the hearing-impaired group, ASSR thresholds more closely resembled behavioural thresholds, with an average difference of 18 dB, which is consistent with recent literature. The literature suggests that better prediction of behavioural thresholds will occur with greater degrees of hearing loss, due to recruitment. The focus in this group also centered on the accurate prediction of the configuration of the hearing loss. It was found that ASSR could reasonably accurately predict the configuration of the hearing loss. In the last instance, monotic single and dichotic multiple ASSR were compared with regard to threshold estimation and prediction of configuration of the hearing loss in the hearing-impaired group. Little difference was reported between the two techniques with regard to the estimation of thresholds in both the normal hearing and hearing impaired groups. In conclusion it was established that monotic ASSR could predict behavioural thresholds of varying degrees and configurations of hearing loss in normal and hearing-impaired subjects with a reasonable amount of accuracy. At this stage, however, more research is required to establish the clinical validity of the procedure, before it is routinely included within an objective test battery. / Dissertation (M (Communication Pathology))--University of Pretoria, 2005. / Speech-Language Pathology and Audiology / Unrestricted