i-Angel Sound

Objective: This study investigated whether auditory training could improve cochlear implant (CI) users' speech recognition in noise and whether training with familiar stimuli in a relatively simple task (closed-set digit recognition) would generalize to improve recognition of unfamiliar stimuli in more complex tasks (open-set sentence recognition). Design: Ten post-lingually deafened adult CI users participated in a repeated-measures design. Baseline speech understanding was established by repeatedly measuring recognition of digits, Hearing in Noise Test (HINT) sentences, and IEEE sentences in both steady-state speech-shaped noise and multi-talker speech babble. Following baseline measures, participants engaged in a home-based training program using custom software. Training consisted of identifying random sequences of three digits presented in speech babble (a closed-set task) for approximately 30 minutes per day, 5 days per week, over a 4-week period (totaling ~10 hours). During training, the signal-to-noise ratio (SNR) was adaptively adjusted based on performance, and feedback was provided. Results: Post-training assessments revealed that digit training in babble significantly improved digit recognition in both the trained condition (babble) and the untrained condition (steady noise). Crucially, these training benefits generalized to open-set sentence recognition tasks: participants demonstrated improved recognition of HINT and IEEE sentences in both types of noise. Furthermore, these performance gains were largely retained in follow-up measures conducted one month after the training concluded. Conclusions: The findings demonstrate that targeted auditory training in noise can significantly enhance speech understanding for CI users in noisy environments. The study specifically highlights that training with simple, familiar stimuli in an easy listening task can effectively generalize to improve performance with more difficult, open-set speech materials.

After implantation, postlingually deafened cochlear implant (CI) patients must adapt to both spectrally reduced and spectrally shifted speech, due to the limited number of electrodes and the limited length of the electrode array. This adaptation generally occurs during the first three to six months of implant use and may continue for many years. To see whether moderate speech training can accelerate this learning process, 16 naïve, normal-hearing listeners were trained with spectrally shifted speech via an eight-channel acoustic simulation of CI speech processing. Baseline vowel and consonant recognition was measured for both spectrally shifted and unshifted speech. Short daily training sessions were conducted over five consecutive days, using four different protocols. For the test-only protocol, no improvement was seen over the five-day period. Similarly, sentence training provided little benefit for vowel recognition. However, after five days of targeted phoneme training, subjects' recognition of spectrally shifted vowels significantly improved in most subjects. This improvement did not generalize to the spectrally unshifted vowel and consonant tokens, suggesting that subjects adapted to the specific spectral shift, rather than to the eight-channel processing in general. Interestingly, significant improvement was also observed for the recognition of spectrally shifted consonants. The largest improvement was observed with targeted vowel contrast training, which did not include any explicit consonant training. These results suggest that targeted phoneme training can accelerate adaptation to spectrally shifted speech. Given these results with normal-hearing listeners, auditory rehabilitation tools that provide targeted phoneme training may be effective in improving the speech recognition performance of adult CI users.