Background and Aim: Contralateral stimulation with noise can improve auditory intensity discrimination. This may be related to function of the efferent system. The purpose of this study was to determine the relationship between the auditory intensity discrimination and the efferent system function.
Methods: Twenty students with normal hearing were included in this descriptive-analytic study. We examined Difference Limen for Intensity (DLI), Otoacoustic Emissions suppression and Speech In Noise. DLI was evaluated with and without contralateral noise stimulation at two different stimulus levels (20, 70 dB SL).
Results: There was significant difference between mean DLI scores of with contralateral masking comparing to without it, which was more prominent as frequency increased. Mean DLI score while masking with white noise was more than mean scores when masking with narrow band noise (p<0.05). Transient evoked otoacoustic emissions responses decreased significantly in amplitude with contralateral masking. (p<0.05)
Conclusion: These results suggest that medial olivocochlear bundle functions as a key role in auditory intensity discrimination.

Background and Aim: As word recognition score test is one of the most important tests in audiologic test battery and there is no study on reliability and validity of existing monosyllabic word lists, we decided to investigate this in people with noise induced hearing loss.

Methods: In this non-randomized descriptive-analytic study, 30 adults with noise induced high frequency hearing loss with the age of 18 to 46 years were evaluated. Construct validity was evaluated by comparing Mosleh lists with list NU-6 and reliability was achieved by test-retest (-two-week interval).

Results: The mean (SD) score of word recognition was 94.01 (3.95) percent for list 2, 90.40 (4.90) percent for list 4, 89.08 (4.43) percent for list 5, and 94.10 (4.11) percent for list 9. A reliability of 94% was achieved in all four lists . Regression analysis revealed that word recognition score (WRS) had decreased in proportion to pure tone average.

Conclusion: Four lists have good construct validity. All word lists are phonetically reliable too.