A comparison between wireless CROS/BiCROS and soft-band BAHA for patients with unilateral hearing loss

Abstract

This study directly compared the performance of a contralateral routing of signal (CROS)/bilateral routing of signal (BiCROS) and a soft-band bone-anchored hearing aid (BAHA) in patients with unilateral sensorineural hearing loss (SNHL) and assessed the relationship between hearing aid benefits and personal factors. Participants with unilateral SNHL were prospectively enrolled in the study and were tested under the following three conditions: unaided, with CROS/BiCROS, and with soft-band BAHA. Sound localization, consonant, hearing in noise, and psychoacoustic tests were performed. Pseudobinaural benefits (e.g., squelch, summation, and head shadow effect) were obtained in both the CROS/BiCROS and soft-band BAHA conditions and compared to the unaided condition. Sound localization ability was not improved in either the CROS/BiCROS condition or soft-band BAHA condition. Rather, sound localization ability was significantly decreased in the CROS/BiCROS setting. A CROS/BiCROS hearing aid and a soft-band BAHA provided additional benefit for speech-in-noise perception when target speech was directed to the impaired ear side. The CROS/BiCROS hearing aid was superior to the soft-band BAHA one in decreasing the head shadow effect, but it appeared to have a negative effect when the noise was delivered to the better ear. The positive and negative effects of CROS/BiCROS for localization and speech perception were significantly correlated with personal factors such as age, hearing threshold in the better ear, and unaided psychoacoustic performances. Despite the lack of device acclimatization, we believe that this study provides counseling information for hearing aid clinics to use in the context of patients with unilateral SNHL.

Fig 1. Localization results.

Panel A shows the mean RMSEs for the three listening groups (unaided, aided with CROS/BiCROS, and aided with BAHA). Panel B shows the hemifield identification scores of the three listening groups. The hemifield identification score was calculated by counting the correct responses when the speaker identified by the listener was in the correct half of the loudspeaker array. Loudspeaker location was categorized as either on the poorer ear side or the better ear side. Error bars indicate SD. Asterisks (*) indicate significant differences, p < 0.05.

Fig 2. Speech perception.

Panel A shows the aided pure-tone threshold at each frequency for the three listening conditions (unaided, aided with CROS/BiCROS, and aided with BAHA). If the pure-tone threshold is scaled out, it is expressed as 110 dB HL (for 250 Hz and 8 kHz) and 125 dB HL (for the rest of the frequencies). Panel B shows consonant perception in quiet and noisy backgrounds for the three listening conditions. Mean and SD are presented as box-and-whisker plots. Panel C shows pseudobinaural benefits of speech perception in noise for the three listening conditions. The SNR threshold was acquired in the presence of noise for the following three conditions: (1) for measuring the summation effect, both speech and noise were presented from the front (F_SF_N); (2) for measuring the squelch effect, speech was presented from one of the two side speakers (± 90°) toward the better ear (NH), while noise was presented from one of the two side speakers (± 90°) toward the poorer ear (HL) (NH_SHL_N); and (3), for measuring the head shadow effect, speech was presented from one of the two side speakers (± 90°) toward the poorer ear, while noise was presented from one of the two side speakers (± 90°) toward the better ear (HL_SNL_N). Asterisks (*) mean a significant difference; p < 0.05 in post-hoc tests using the Bonferroni correction.

Fig 3. Psychoacoustic performance.

SRD thresholds (A) and TMD thresholds (B) are shown for the three listening conditions. For the SRD test, a higher detection threshold indicates better SMD performance. For the TMD test, a more negative detection threshold implies better TMD performance. An asterisk (*) indicates a significant difference between two groups in post-hoc analysis (p-value was 0.05/3 based on Bonferroni correction).

Fig 4. Subjective assessments.

Panel A shows the study participant preferences for wireless CROS/BiCROS and soft-band BAHA. Panel B shows a six-item VAS for assessing background noise and sound quality in the three listening conditions. A higher score indicates that the sound was perceived better.