Melody and chord discrimination of cochlear implant users in different pitch ranges.

OBJECTIVE: The study assesses the ability of cochlear implant (CI) recipients to discriminate music excerpts, namely melodies and chords. Natural instrument recordings were used to test whether an improved fine-structure transmission is beneficial for this task at low pitches. METHODS: Seventeen CI recipients using either a continuously interleaved strategy (CIS) strategy or fine-structure coding (FSP) had to discriminate melody pairs played by the violin or the cello, and pairs of chords differing at high or low pitches. The examples were taken from the Mu.S.I.C. perception test. RESULTS: In the melody task, no differences were found according to pitch range or processing strategy. In the chords task, changes in the low-pitch range provided a significantly greater difficulty for CI recipients using the CIS stategy and correct detection was reduced by 11.1% compared to the detection of high-pitch changes. This drop in performance was reduced in the FSP users to 7.4% correct and was statistically not significant. CONCLUSIONS: When musical chords played with natural instrument are discriminated by CI users, a fine-structure coding strategy provides some benefit at low pitches. No benefit was found in the discrimination of unaccompanied melodies.

Logatome discrimination in cochlear implant users: subjective tests compared to the mismatch negativity.

This paper describes a logatome discrimination test for the assessment of speech perception in cochlear implant users (CI users), based on a multilingual speech database, the Oldenburg Logatome Corpus, which was originally recorded for the comparison of human and automated speech recognition. The logatome discrimination task is based on the presentation of 100 logatome pairs (i.e., nonsense syllables) with balanced representations of alternating "vowel-replacement" and "consonant-replacement" paradigms in order to assess phoneme confusions. Thirteen adult normal hearing listeners and eight adult CI users, including both good and poor performers, were included in the study and completed the test after their speech intelligibility abilities were evaluated with an established sentence test in noise. Furthermore, the discrimination abilities were measured electrophysiologically by recording the mismatch negativity (MMN) as a component of auditory event-related potentials. The results show a clear MMN response only for normal hearing listeners and CI users with good performance, correlating with their logatome discrimination abilities. Higher discrimination scores for vowel-replacement paradigms than for the consonant-replacement paradigms were found. We conclude that the logatome discrimination test is well suited to monitor the speech perception skills of CI users. Due to the large number of available spoken logatome items, the Oldenburg Logatome Corpus appears to provide a useful and powerful basis for further development of speech perception tests for CI users.

Development of a speaker discrimination test for cochlear implant users based on the Oldenburg Logatome corpus.

The purpose of the study was to develop a speaker discrimination test for cochlear implant (CI) users. The speech material was drawn from the Oldenburg Logatome (OLLO) corpus, which contains 150 different logatomes read by 40 German and 10 French native speakers. The prototype test battery included 120 logatome pairs spoken by 5 male and 5 female speakers with balanced representations of the conditions 'same speaker' and 'different speaker'. Ten adult normal-hearing listeners and 12 adult postlingually deafened CI users were included in a study to evaluate the suitability of the test. The mean speaker discrimination score for the CI users was 67.3% correct and for the normal-hearing listeners 92.2% correct. A significant influence of voice gender and fundamental frequency difference on the speaker discrimination score was found in CI users as well as in normal-hearing listeners. Since the test results of the CI users were significantly above chance level and no ceiling effect was observed, we conclude that subsets of the OLLO corpus are very well suited to speaker discrimination experiments in CI users.