Effect of inter-aural modulation depth difference on interaural time difference thresholds for speech: An observational study.

Background: The temporal envelope (ENV) plays a vital role in conveying inter-aural time difference (ITD) in many clinical populations. However, the presence of background noise and electronic features, such as compression, reduces the modulation depth of ENV to a different degree in both ears. The effect of ENV modulation depth differences between the ears on ITD thresholds is unknown; therefore, this was the aim of the current study's investigation. Methods: Six normally hearing young adults (age range 20-30 years) participated in the current study. Six vowel-consonant-vowel (VCV) (/aka/, /aga/, /apa/, /aba/, /ata/, /ada/) tokens were used as the probe stimuli. ENV depth of VCV tokens was smeared by 0%, 29%, and 50%, which results in 100%, 71%, and 50% of the original modulation depth. ITD thresholds were estimated as a function of the difference in temporal ENV depth between the ears, wherein in one ear the modulation depth was retained at 100% and in the other ear, the modulation depth was changed to 100%, 71%, and 50%. Results: Repeated measures of ANOVA revealed a significant main effect of interaural modulation depth differences on the ITD threshold (F(2,10)= 9.04, p= 0.006). ITD thresholds increased with an increase in the inter-aural modulation depth difference. Conclusion: Inter-aural ENV depth is critical for ITD perception.

Comparison of temporal fine structure sensitivity and concurrent vowel perception between children with and without reading disability.

Background: Children with reading disabilities (RD) exhibit difficulty in perceiving speech in background noise due to poor auditory stream segregation. There is a dearth of literature on measures of temporal fine structure sensitivity (TFS) and concurrent vowel perception abilities to assess auditory stream segregation in children with reading disabilities. Hence the present study compared temporal fine structure sensitivity (TFS) and concurrent vowel perception abilities between children with and without reading deficits. Method: The present research consisted of a total number of 30 participants, 15 children with reading disabilities (RD) and fifteen typically developing (TD) children within the age range of 7-14 years and were designated as Group 1 and Group 2 respectively. Both groups were matched for age, grade, and classroom curricular instructions. The groups were evaluated for TFS and concurrent vowel perception abilities and the performance was compared using independent 't' test and repeated measure ANOVA respectively. Results: Results revealed that the children with RD performed significantly (p < 0.001) poorer than TD children on both TFS and concurrent vowel identification task. On concurrent vowel identification tasks, there was no significant interaction found between reading ability and F0 difference suggesting that the trend was similar in both the groups. Conclusion: The study concludes that the children with RD show poor temporal fine structure sensitivity and concurrent vowel identification scores compared to age and grade matched TD children owing to poor auditory stream segregation in children with RD.

Effect of systematic desensitization training on acceptable noise levels in adults with normal hearing sensitivity.

CONTEXT: The willingness of a person to accept noise while listening to speech can be measured using the acceptable noise level (ANL) test. Individuals with poor ANL are unlikely to become successful hearing aid users. Hence, it is important to enhance the individual's ability to accept noise levels. The current study was an attempt to investigate whether systematic desensitization training can improve the ANL in individuals having high ANL. AIMS: To investigate the effect of systematic desensitization training on ANLs in individuals with normal hearing sensitivity. SETTINGS AND DESIGN: Observational study design. MATERIALS AND METHODS: Thirty-eight normally hearing adults within the age range of 18-25 years participated in the study. Initially, baseline ANL was measured for all participants. Based on the baseline ANL, participants were categorized into three groups; low ANL, mid ANL, and high ANL. The participants with high ANL were trained using systematic desensitization procedure whereas, individuals with low and mid ANL did not undergo any training and served as the comparison groups. After the training period, ANL was measured again for all the participants. STATISTICAL ANALYSIS USED: Repeated measures of analysis of variance with follow up paired "t" test. RESULTS: Analysis revealed a significant main effect of systematic desensitization training on ANL. There was a significant improvement in ANL in participants with high ANL. However, there was no significant difference in ANL between baseline and follow-up session in individuals with low and mid ANL. CONCLUSIONS: Systematic desensitization training can facilitate ANL, thereby enhancing the individual's ability to accept the noise levels. This enhanced ANL can facilitate better hearing aid fitting and acceptance.