Nine adults with single-sided deafness previously implanted with a Baha were given a two-week trial with a CROS hearing aid and tested in unaided and aided conditions. Both devices were compared on head shadow effect reduction, speech perception measures, self-assessment questionnaires, and daily diaries. The CROS reduced the head shadow effect for more frequencies than the Baha. Participants performed well across all conditions with speech to the poor ear in quiet. The QuickSIN showed both devices adversely affected speech perception with noise to the poor ear; the CROS was more disadvantageous. Neither device improved speech perception with noise to the better ear. The BBSS and SSQ demonstrated subjective benefit and the diaries indicated frequent use of both devices. Five participants preferred the CROS for sound quality; three preferred the Baha for comfort. As both devices seem comparable, a CROS should be the first intervention option recommended before considering Baha surgery.

Spatial hearing is crucial in real life but deteriorates in participants with severe sensorineural hearing loss or single-sided deafness. This ability can potentially be improved with a unilateral cochlear implant (CI). The present study investigated measures of sound localization in participants with single-sided deafness provided with a CI. Sound localization was measured separately at eight loudspeaker positions (4°, 30°, 60°, and 90°) on the CI side and on the normal-hearing side. Low- and high-frequency noise bursts were used in the tests to investigate possible differences in the processing of interaural time and level differences. Data were compared to normal-hearing adults aged between 20 and 83. In addition, the benefit of the CI in speech understanding in noise was compared to the localization ability. Fifteen out of 18 participants were able to localize signals on the CI side and on the normal-hearing side, although performance was highly variable across participants. Three participants always pointed to the normal-hearing side, irrespective of the location of the signal. The comparison with control data showed that participants had particular difficulties localizing sounds at frontal locations and on the CI side. In contrast to most previous results, participants were able to localize low-frequency signals, although they localized high-frequency signals more accurately. Speech understanding in noise was better with the CI compared to testing without CI, but only at a position where the CI also improved sound localization. Our data suggest that a CI can, to a large extent, restore localization in participants with single-sided deafness. Difficulties may remain at frontal locations and on the CI side. However, speech understanding in noise improves when wearing the CI. The treatment with a CI in these participants might provide real-world benefits, such as improved orientation in traffic and speech understanding in difficult listening situations.