Preferred Name
Mariam Mohamed
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Date of Graduation
5-14-2026
Semester of Graduation
Spring
Degree Name
Doctor of Audiology (AuD)
Department
Department of Communication Sciences and Disorders
First Advisor
Ayasakanta Rout
Abstract
Background: Directional microphones in hearing aids are a well-established strategy for enhancing speech intelligibility in background noise. While previous studies have examined the effects of hair, spectacles, and earmold venting, no systematic research has addressed whether head coverings, commonly worn for cultural, religious, or personal reasons, affect directional performance.
Objective: This study aimed to determine whether a thin cotton head covering alters the directivity index (DI) of premium receiver-in-canal hearing aids from four leading manufacturers, using laboratory-controlled conditions.
Methods: A Knowles Electronics Manikin for Acoustic Research (KEMAR) was positioned within a sound-treated room to measure DI for both omnidirectional and fixed directional microphone settings, comparing exposure conditions with and without the cotton head covering. Measurements were collected at 500, 1000, 2000, and 4000 Hz with all adaptive microphone features turned off. DI was calculated from root-mean-square levels recorded at 30° increments and analyzed using a 2×2 repeated-measures design.
Results: Directional adjustments of the microphones caused a consistent and highly significant increase in DI (p< 0.001, partial eta-squared=0.977) across all test frequencies and hearing aid manufacturers. There was not a statistically significant difference between the two testing conditions (p=0.615). In addition, there were no statistically significant interactions between the head covering condition and either the directionality of the microphones, the test frequencies, or the hearing aid manufacturers. However, the results indicated that the microphones were less sensitive when they were covered, which could result in a small decrease in perceived volume. Additionally, there were statistically significant differences between the hearing aid manufacturers (p< 0.001), with Manufacturer D having the lowest DI compared to manufacturers A, B, and C.
Conclusion: A lightweight cotton scarf offers no significant effect on the directional advantage provided by current hearing aid technology when tested under controlled conditions. Audiologists can confidently inform individuals that such soft, breathable coverings will not appreciably lessen directional gain. Nevertheless, confirmation during routine verification of the individual fitting continues to be prudent. Manufacturer differences should be considered when counseling patients who prioritize hearing-in-noise performance.
