The effect of hearing aid microphone directivity on localization and hearing quality in individuals with unilateral and bilateral hearing loss

The localization and lateralization abilities of individuals using hearing aids may differ from those with normal hearing. Hearing quality and speech understanding performance are also key parameters in hearing aid applications. This study aimed to evaluate the effects of microphone directionality settings in hearing aids on individuals' localization, lateralization, and hearing quality. Participants were grouped into three: individuals with unilateral hearing loss using hearing aids, those with bilateral hearing loss using bilateral hearing aids, and individuals with normal hearing. A two-phase adjustment was applied to the microphone directionality settings of the hearing aids. Pre- and post-adjustment evaluations included lateralization (via Weber test), speech perception, spatial perception, and hearing quality (using the Turkish version of the Speech, Spatial and Qualities of Hearing Scale – SSQ), and localization (using the Auditory Localization Scale). SSQ total scores were highest in the control group (8.58 ± 0.28), moderate in the unilateral group (6.36 ± 0.53), and lowest in the bilateral group (5.56 ± 1.02) in both measurements. The change between the two measurements was more significant in the bilateral group (p < 0.0001). Localization total scores in the first measurement were highest in the bilateral group (49.68 ± 2.83) and lowest in the control group (47.4 ± 1.4) (p < 0.0001). A significant improvement was observed in the SSQ communication subscale of the bilateral group after switching to directional microphone use (4.82 ± 1.62 → 5.32 ± 1.35; p = 0.001). In the unilateral group, a moderate negative correlation was found between the outdoor localization subscale and the SSQ communication change score (r = -0.466, p = 0.010).This study demonstrates that using a directional microphone, particularly in bilateral hearing aid users, positively impacts speech intelligibility and spatial hearing abilities. Unilateral users also benefited from microphone directionality to a limited extent. However, their performance generally remained lower than that of individuals with normal hearing. The results emphasize the importance of considering microphone directionality settings in personalized hearing aid fitting processes.