Effects of Auditory Fatigue on Central Auditory Processing in Adults With Normal Hearing

This arm will include 30 adults aged 18-40 years with normal peripheral hearing who work in occupations requiring sustained verbal communication, active speech listening, and auditory attention. Participants will include simultaneous interpreters, speech and language therapists, special education teachers, and psychologists conducting regular client consultations. All participants will complete a standardized 60-minute experimental auditory fatigue listening task. Central auditory processing performance will be assessed using the Gaps-in-Noise Test (GIN), Frequency Pattern Test (FPT), and Duration Pattern Test (DPT) before and after the listening task. Perceived auditory fatigue, listening effort, and task demands will also be evaluated using Visual Analog Scales (VAS).

All participants will complete a standardized 60-minute experimental listening task designed to induce acute auditory fatigue. The task will involve sustained listening to Turkish Hearing in Noise Test (HINT-TR) speech materials presented with multi-talker babble noise. The same listening protocol will be administered to participants in both occupational groups under standardized conditions. The intervention will be performed once, following baseline auditory assessments. Immediately after the task, central auditory processing performance will be reassessed using the GIN, FPT, and DPT. Subjective auditory fatigue, listening effort, and perceived task demands will also be evaluated using Visual Analog Scales (VAS) before and after the intervention.

This arm will include 30 adults aged 18-40 years with normal peripheral hearing whose occupations do not require intensive and sustained verbal communication or continuous active speech listening. Participants will be selected to achieve comparable age, sex, and educational characteristics between occupational groups where possible. All participants will complete the same standardized 60-minute experimental auditory fatigue listening task administered to the high occupational listening demands group. Central auditory processing performance will be assessed using the Gaps-in-Noise Test (GIN), Frequency Pattern Test (FPT), and Duration Pattern Test (DPT) before and after the listening task. Perceived auditory fatigue, listening effort, and task demands will also be evaluated using Visual Analog Scales (VAS).

All participants will complete a standardized 60-minute experimental listening task designed to induce acute auditory fatigue. The task will involve sustained listening to Turkish Hearing in Noise Test (HINT-TR) speech materials presented with multi-talker babble noise. The same listening protocol will be administered to participants in both occupational groups under standardized conditions. The intervention will be performed once, following baseline auditory assessments. Immediately after the task, central auditory processing performance will be reassessed using the GIN, FPT, and DPT. Subjective auditory fatigue, listening effort, and perceived task demands will also be evaluated using Visual Analog Scales (VAS) before and after the intervention.

Temporal resolution will be assessed using the Gaps-in-Noise (GIN) Test. The outcome will be the change in gap detection threshold, measured in milliseconds (ms), calculated as the post-intervention threshold minus the baseline threshold. Lower thresholds indicate better temporal resolution. Changes will be compared between the two occupational groups.

Temporal pattern recognition based on frequency variations will be assessed using the Frequency Pattern Test (FPT). Performance will be expressed as the percentage of correctly identified frequency patterns, ranging from 0% to 100%. The outcome will be calculated as the post-intervention percentage minus the baseline percentage. Higher percentages indicate better performance. Changes will be compared between occupational groups.

Temporal pattern recognition based on sound duration will be assessed using the Duration Pattern Test (DPT). Performance will be expressed as the percentage of correctly identified duration patterns, ranging from 0% to 100%. The outcome will be calculated as the post-intervention percentage minus the baseline percentage. Higher percentages indicate better performance. Changes will be compared between occupational groups.

Perceived auditory fatigue will be assessed using a 100-mm Visual Analog Scale (VAS) before and immediately after the experimental listening task. Participants will rate their perceived level of auditory fatigue on a continuous scale ranging from 0 mm (no auditory fatigue at all) to 100 mm (extreme auditory fatigue). Higher scores indicate greater perceived auditory fatigue. The outcome will be calculated as the post-intervention VAS score minus the baseline VAS score, expressed in millimeters (mm). Positive change scores indicate an increase in perceived auditory fatigue following the listening task.

Perceived listening effort will be assessed using a 100-mm Visual Analog Scale (VAS) before and immediately after the experimental listening task. Participants will rate their perceived level of listening effort on a continuous scale ranging from 0 mm (no listening effort at all) to 100 mm (extremely high listening effort). Higher scores indicate greater perceived listening effort. The outcome will be calculated as the post-intervention VAS score minus the baseline VAS score, expressed in millimeters (mm). Positive change scores indicate an increase in perceived listening effort following the listening task.