Tehran University of Medical Sciences Auditory and Vestibular Research 2423-480X 34 2 2024 08 27 151 157 EN Jafar Aghazadeh Department of Audiology, School of Rehabilitation, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Saeideh Mehrkian Department of Audiology, School of Rehabilitation, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran AND Department of Clinical Sciences, School of Rehabilitation, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Enayatollah Bakhshi Department of Biostatistics and Epidemiology, School of Education Sciences and Social Welfare, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Talieh Zarifian Department of Speech Therapy, School of Rehabilitation Sciences, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran 2024 06 22 2024 08 04 Background and Aim: Many older adults experience difficulty in speech perception in noisy environments and fast speech. Speech perception is dependent on bottom-up and top-down auditory processing information. This study aimed to investigate the relationship between Interaural Time Difference (ITD) and speech processing speed in older adults with difficulty in speech perception in noise. Methods: In this study, 36 Iranian older adults with normal hearing (23 men and 13 women) aged 65–75 years who had complaints about the difficulty with speech perception in noise, participated. The ITD test with two stimuli (high-pass and low-pass noise) was used to asess the auditory localization ability. Time-Compressed Speech Test (TCST) and reaction time test were used to measure their speech processing speed. Pearson correlation test was performed to examine the relationship between ITD and speech processing speed. Results: The auditory localization errors were more significant for ITDs with low-pass noise than high-pass noise. The results showed a negative correlation between localization errors and the TCST score at time compression ratios of 40% (p=0.005) and 60% (p=0.002). The highest correlation was observed between ITD (low-pass noise) and the TCST score at the time compression ratio of 60% in the right ear (r=–0.66). The mean ITD errors were not significantly correlated to the reaction time test score (p>0.05). Conclusion: Word recognition in the elderly declines with increasing speech rate. The findings of this study can be used in clinical practice for consultation and rehabilitation of older adults with communication difficulties. https://avr.tums.ac.ir/index.php/avr/article/view/1325