Integration of fundamental frequency and voice-onset-time to voicing categorization: Listeners with normal hearing and bimodal hearing configurations.

This study investigates the integration of word-initial fundamental frequency (F0) and voice-onset-time (VOT) in stop voicing categorization for adult listeners with normal hearing (NH) and unilateral cochlear implant (CI) recipients utilizing a bimodal hearing configuration [CI + contralateral hearing aid (HA)]. Categorization was assessed for ten adults with NH and ten adult bimodal listeners, using synthesized consonant stimuli interpolating between /ba/ and /pa/ exemplars with five-step VOT and F0 conditions. All participants demonstrated the expected categorization pattern by reporting /ba/ for shorter VOTs and /pa/ for longer VOTs, with NH listeners showing more use of VOT as a voicing cue than CI listeners in general. When VOT becomes ambiguous between voiced and voiceless stops, NH users make more use of F0 as a cue to voicing than CI listeners, and CI listeners showed greater utilization of initial F0 during voicing identification in their bimodal (CI + HA) condition than in the CI-alone condition. The results demonstrate the adjunctive benefit of acoustic hearing from the non-implanted ear for listening conditions involving spectrotemporally complex stimuli. This finding may lead to the development of a clinically feasible perceptual weighting task that could inform clinicians about bimodal efficacy and the risk-benefit profile associated with bilateral CI recommendation.

Synchronized Automatic Gain Control in Bilateral Cochlear Implant Recipients Yields Significant Benefit in Static and Dynamic Listening Conditions.

Individuals with bilateral cochlear implants (BiCIs) rely mostly on interaural level difference (ILD) cues to localize stationary sounds in the horizontal plane. Independent automatic gain control (AGC) in each device can distort this cue, resulting in poorer localization of stationary sound sources. However, little is known about how BiCI listeners perceive sound in motion. In this study, 12 BiCI listeners' spatial hearing abilities were assessed for both static and dynamic listening conditions when the sound processors were synchronized by applying the same compression gain to both devices as a means to better preserve the original ILD cues. Stimuli consisted of band-pass filtered (100-8000 Hz) Gaussian noise presented at various locations or panned over an array of loudspeakers. In the static listening condition, the distance between two sequentially presented stimuli was adaptively varied to arrive at the minimum audible angle, the smallest spatial separation at which the listener can correctly determine whether the second sound was to the left or right of the first. In the dynamic listening condition, participants identified if a single stimulus moved to the left or to the right. Velocity was held constant and the distance the stimulus traveled was adjusted using an adaptive procedure to determine the minimum audible movement angle. Median minimum audible angle decreased from 17.1° to 15.3° with the AGC synchronized. Median minimum audible movement angle decreased from 100° to 25.5°. These findings were statistically significant and support the hypothesis that synchronizing the AGC better preserves ILD cues and results in improved spatial hearing abilities. However, restoration of the ILD cue alone was not enough to bridge the large performance gap between BiCI listeners and normal-hearing listeners on these static and dynamic spatial hearing measures.

Duration of Processor Use Per Day Is Significantly Correlated With Speech Recognition Abilities in Adults With Cochlear Implants.

OBJECTIVE: Quantify the relationship between average hours of processor use per day and measures of speech recognition in post-lingually deafened adults with cochlear implants. SETTING: Cochlear implant (CI) program at a tertiary medical center. PATIENTS: Three hundred adult (mean age = 64, 130 women) CI users were included. MAIN OUTCOME MEASURES: Correlation analyses were completed for CI-aided speech recognition (Consonant-Nucleus-Consonant [CNC] monosyllables and AzBio sentences) at approximately 12 months post-implantation and average hours of processor use per day, which was extracted from the CI programming software. RESULTS: Average processor use was 10.2 hours per day (range, 0.1-22.7), and average speech recognition scores were 49.9 and 61.7% for CNC and AzBio sentence recognition, respectively. We found a strong, significant correlation between hours of processor use per day and consonant-nucleus-consonant (CNC) word recognition (rs = 0.61, p < 0.0001) and AzBio sentence recognition (rs = 0.56, p < 0.0001). CONCLUSIONS: Results suggest that highest speech recognition outcomes are correlated with greater than 10 hours of CI use per day. Further research is needed to assess the causal link between daily CI use and speech recognition abilities.