Evaluation of the effects of different amplification systems on localization and speech understanding in noise in individuals with single sided deafness

Individuals with single-sided deafness (SSD) can not acquire binaural cues that individuals with bilaterally normal hearing reach because the auditory signals are not processed in both ears. Although it does not provide binaural hearing, Contralateral Routing of Signals (CROS) hearing aids that do not require surgical intervention and Bone-Anchored Hearing Aids (BAHA) with soft bands are used in monaural listeners to eliminate the disadvantage caused by the head shadow effect. The present study aimed to compare the effects of CROS and BAHA amplification systems on auditory localization and speech perception in noise in 15 individuals aged 20-50 years who have SSD and have not used any amplification systems before. Localization tests in the Auditory Speech Sound Evaluation (ASSE) test battery included in Audiqueen software were used to assess localization skills. The Hearing in Noise Test-Adult version (HINT-A) was used to evaluate speech perception skills in noisy environments. While significantly better scores were found in the Azimuth Localization Test with soft band BAHA (p<0.05), the Interaural Loudness Difference (ILD) Localization Test indicated no significant difference between the three conditions (p>0.05). In the Speech Perception in Noise Test, a significant improvement was shown with CROS and BAHA devices when the noise was sent from the front of the participants (p<0.05). There was a statistically significant difference between the comparison without any device condition and with CROS and BAHA devices conditions when the noise was sent from the ipsilateral ear of participants (p<0.05). Significantly better scores were found with soft band BAHA among both device conditions. When the noise was sent from the contralateral ear, there was no significant difference between the three conditions (p>0.05). Considering the satisfaction scores of the participants in terms of Localization and Speech Perception in Noise Tests, for both tests, the score given for the soft band BAHA was found as significantly better than the CROS hearing aid, and the score given for the CROS hearing aid was significantly better than the score given for the without any device condition (p<0.05). These findings indicated that amplification systems, which provide contralateral transmission in individuals with SSD, have a positive effect on speech perception in noise performance and that localization skills can be improved with the usage of soft band BAHA. It can be suggested that individuals with SSD could crucial benefit from the BAHA and CROS hearing aids which provide contralateral transmission. Keywords: Binaural hearing, Single-sided deafness, sound localization, speech perception in noise, contralateral transmission.