BACKGROUND AND OBJECTIVES: The stimulus signals delivered in cochlear implant (CI) systems are generally derived by sampling the temporal envelope of each channel at some constant rate and using its intensity to control the stimulation current level delivered to the corresponding electrode site. The objective of the study was to investigate speech recognition performance of cochlear implant users in quiet and noisy environments using either moderate or high rates of electrical stimulations. MATERIALS AND METHODS: Six post-lingually deafened adult users of the Nucleus CI24 cochlear implant (Contour(R) electrode array, Cochlear(TM), Macquarie Park, Australia) with the Freedom(R) speech processor participated in the study. Stimulation rates of 900 and 2400 pulses-per-second/channel (pps/ch) were used after both stimulation programs were balanced for loudness. Monosyllabic word and sentence recognition scores in quiet and noisy environments were evaluated for each stimulation program after two months of practice. Subjects were also asked to respond to a questionnaire to examine their preference to any stimulation rate in different hearing conditions. RESULTS: Word recognition scores for monosyllabic words in quiet conditions with the 900 stimulation rate was better than that of the 2400 stimulation rate, although no significant differences between them were found for sentence test in noise. A survey questionnaire indicated that most subjects preferred the 900 stimulation rate to the 2400 stimulation rate, especially in quiet conditions. CONCLUSIONS: Most subjects indicated a preference for 900 pps/ch rate in quiet conditions. It is recommended to remap at 900 pps/ch for those CI users whose performance in quiet conditions is less than ideal.
Adult ; Cochlear Implants ; Correction of Hearing Impairment ; Electric Stimulation ; Electrodes ; Hearing ; Humans ; Noise ; Speech Perception ; Sydnones ; Surveys and Questionnaires

OBJECTIVES: Although the cochlear implant (CI) is successful for understanding speech in patients with severe to profound hearing loss, listening to music is a challenging task to most CI listeners. The purpose of this study was to assess music perception ability and to provide clinically useful information regarding CI rehabilitation. METHODS: Ten normal hearing and ten CI listeners with implant experience, ranging 2 to 6 years, participated in the subtests of pitch, rhythm, melody, and instrument. A synthesized piano tone was used as musical stimuli. Participants were asked to discriminate two different tones during the pitch subtest. The rhythm subtest was constructed with sets of five, six, and seven intervals. The melody & instrument subtests assessed recognition of eight familiar melodies and five musical instruments from a closed set, respectively. RESULTS: CI listeners performed significantly poorer than normal hearing listeners in pitch, melody, and instrument identification tasks. No significant differences were observed in rhythm recognition between groups. Correlations were not found between music perception ability and word recognition scores. CONCLUSION: The results are consistent with previous studies that have shown that pitch, melody, and instrument identifications are difficult to identify for CI users. Our results can provide fundamental information concerning the development of CI rehabilitation tools.
Adult ; Cochlear Implants ; Hearing ; Hearing Loss ; Humans ; Music ; Perception

BACKGROUND AND OBJECTIVES: The purpose of this study was to compare speech audiometry test results of the conventional Hahm's list with those of Korean standard word lists for adults (KS-WL-A) using both live voice and compact disc (CD) speech presentation modes. SUBJECTS AND METHOD: Eighty patients with sensorineural hearing loss and 23 control subjects with normal hearing participated in the study. Each hearing loss group comprised 20 subjects (mild, moderate, moderately severe, and severe hearing loss groups). Speech audiometry was performed to measure the speech recognition threshold (SRT) and word recognition score. KS-WL-A was presented either through a live voice mode or recorded CD materials. Test words from Hahm's list were presented using the live voice mode only. Pure tone audiometry was also conducted for all subjects. RESULTS: Differences between the SRT and pure tone average were within 6 dB in all subgroups in all three stimulation methods, indicating high reliability of the SRT in both the conventional and Korean standard methods. The moderate, moderately severe, and severe hearing loss groups showed lower word recognition scores in the CD mode with KS-WL-A than with the two live voice modes. CONCLUSION: Both the live voice mode and CD mode showed reliable speech audiometry test results in normal and hearing-impaired subjects. Although the CD mode is recommended to standardize test methods and reduce test errors, the live voice mode might be more effective for patients with moderate to severe hearing loss.
Adult* ; Audiometry ; Audiometry, Speech* ; Compact Disks ; Hearing Loss ; Hearing Loss, Sensorineural ; Hearing* ; Humans ; Speech Discrimination Tests ; Speech Reception Threshold Test ; Voice