[Development of Mandarin tonal identification in noise test materials].

OBJECTIVE: The aim of this study was to develop comprehensive test material for Mandarin tone identification in noise (M-TINT) based on the linguistic characteristics in Chinese. METHODS: In keeping with both the reliability and efficiency in clinical practice, a primary list consisted of 320 words(80 syllables in four tones each) was designed according to the following principles: shortness of the lists, word familiarity and with a meaning in all four tones. The digital sound file was recorded by a male speaker and a female speaker (both of them are radio broadcaster). RESULTS: The tonal identification material database, which included 288 items (72 loudness-balanced syllables in all 4 Mandarin tones) was established by digital filler and balanced for equal loudness. The complete material was recorded in two CDs in a male version and a female version. The speaker-specific masking noises were generated by filtering Gaussian white noise to the speaker's long-term average speech spectrum (LTASS) and by scaling the masking noises to the same RMS amplitudes, as those of the speech, in order to acquire the effective sound masking. The speaker-specific masking noises could be able or disable during the word presentation. The sound pressure level could be selected concerning on the test setting. CONCLUSIONS: The mandarin tonal identification materials were designed by both the tonal acoustic properties and the psychophysics characteristic of adults. It is an useful speech test in clinical work and research, and can potentially be used as the basic list for other tonal language identification test in the future.

[Effects of temporal fine structure stimulation on Mandarin identification in cochlear implant users].

OBJECTIVE: To assess the contribution of the temporal fine structure cues on speech recognition, especially tone perception of cochlear implant users whose native language is Mandarin Chinese. METHODS: Twelve Mandarin speaking users of the MED-EL COMBI 40+ cochlear implants with the standard COMBI 40+ electrode array participated in the study. The subjects were followed up and studied using the longitudinal method for six weeks to compare the difference in speech identification results between fine structure processing (FSP) and continuous interleaved sampler (CIS). The test battery comprised two objective speech tests, including tone identification in quiet as well as a sentence recognition task in quiet and noise. RESULTS: The scores of acute speech test: after replacing FSP strategy, the acute tone test results were similar to that of daily used CIS strategy(male version t = 0.791, P = 0.446;female version t = 0.679, P = 0.511), but the scores of MHINT were decreased significantly (t = -4.365, P = 0.001). The scores of long-lasting speech test were as follows the scores of tone identification test were sharply increased after subjects used the new coding strategy for six weeks continuously(male version t = 3.023, P = 0.018;female version t = 3.883, P = 0.003) and the MHIN results were similar to that of daily used CIS strategy(t = 1.475, P = 0.173). CONCLUSION: The extraction of temporal fine structure cues supplemented in speech processing strategy of cochlear implant benefits the improvements in tone perception and the understanding of speech in cochlear implant recipients, which can further promotes their quality of life.

Electric-acoustic pitch comparisons in single-sided-deaf cochlear implant users: frequency-place functions and rate pitch.

Eight cochlear implant users with near-normal hearing in their non-implanted ear compared pitch percepts for pulsatile electric and acoustic pure-tone stimuli presented to the two ears. Six subjects were implanted with a 31-mm MED-EL FLEX(SOFT) electrode, and two with a 24-mm medium (M) electrode, with insertion angles of the most apical contacts ranging from 565° to 758°. In the first experiment, frequency-place functions were derived from pure-tone matches to 1500-pps unmodulated pulse trains presented to individual electrodes and compared to Greenwood's frequency position map along the organ of Corti. While the overall median downward shift of the obtained frequency-place functions (-0.16 octaves re. Greenwood) and the mean shifts in the basal (<240°; -0.33 octaves) and middle (-0.35 octaves) regions were statistically significant, the shift in the apical region (>480°; 0.26 octaves) was not. Standard deviations of frequency-place functions were approximately half an octave at electrode insertion angles below 480°, increasing to an octave at higher angular locations while individual functions were gradually leveling off. In a second experiment, subjects matched the rates of unmodulated pulse trains presented to individual electrodes in the apical half of the array to low-frequency pure tones between 100 Hz and 450 Hz. The aim was to investigate the influence of electrode place on the salience of temporal pitch cues, for coding strategies that present temporal fine structure information via rate modulations on select apical channels. Most subjects achieved reliable matches to tone frequencies from 100 Hz to 300 Hz only on electrodes at angular insertion depths beyond 360°, while rate-matches to 450-Hz tones were primarily achieved on electrodes at shallower insertion angles. Only for electrodes in the second turn the average slopes of rate-pitch functions did not differ significantly from the pure-tone references, suggesting their use for the encoding of within-channel fine frequency information via rate modulations in temporal fine structure stimulation strategies.

Effects of temporal fine structure stimulation on Mandarin speech recognition in cochlear implant users.

CONCLUSION: The investigated experimental coding strategies significantly improved tone identification as compared with the participants' everyday audio processor settings. However, this benefit could not be attributed entirely to temporal fine structure stimulation but seems to be caused by decreasing the lower corner frequency of the filter bank. The 6 week habituation period used in this study might have been too short to allow the listeners to derive additional lexical information from the unfamiliar stimulation patterns. OBJECTIVES: To evaluate a cochlear implant coding strategy that explicitly conveys temporal fine structure information in the context of the tonal language Mandarin. METHODS: The study was designed as a longitudinal, monocentric, prospective, controlled, and randomized cross-over study and included 12 postlingually deafened adults, who were experienced cochlear implant users. Two experimental coding strategies, one of which explicitly presents temporal fine structure information, were compared to the participants' personal TEMPO+ speech processors, which do not convey fine structure information. RESULTS: Both experimental coding strategies improved tone identification by approximately 11 percentage points. This improvement was significant in the female speaker test. Sentence perception, as assessed with the M-HINT test, and quality of life scores were identical with all three coding strategies.

Visualizing phase relations of the vocal folds by means of high-speed videoendoscopy.

OBJECTIVES: To present a method called Fourier image (FI) for analyzing high-speed videoendoscopy recordings. These false-color images visualize functional vocal fold properties and allow the quantification of phase relations. Furthermore, reference data for phase asymmetries in normophonic speakers as assessed with this method are provided. STUDY DESIGN: Prospective study. METHODS: Phase relations between parts of the vocal folds were assessed using Fourier analysis of the grayscale fluctuations of corresponding pixel within the endoscopic high-speed videos. This phase information was displayed by means of colors and can thus be used to quantify left-right or anterior-posterior phase asymmetries. These phase relations were assessed in 11 normophonic speakers. RESULTS: Several instructive examples are given, which demonstrate how the FIs can be interpreted. From the cohort of clinically normophonic speakers, all but one displayed at least some extent of phase asymmetry. CONCLUSIONS: The method presented herein can be used to display functional vocal fold properties including the absence of oscillation, glottal insufficiency, and phase relations within one single image. The reference data showed that phase asymmetries seem to be frequent even in normophonic speakers.

The contribution of apical stimulation to Mandarin speech perception in users of the MED-EL COMBI 40+ cochlear implant.

CONCLUSION: Not stimulating the apical cochlear region in tonal language speaking cochlear implantees significantly reduces discrimination of Mandarin vowels. The data presented here suggest that electrode arrays that allow complete cochlear coverage with stimulation pulses seem to be preferable over shorter arrays for use in cochlear implant (CI) indications. OBJECTIVE: To assess the contribution of electrical stimulation beyond the first cochlear turn on tonal language speech perception. METHODS: Twelve Mandarin-speaking users of the MED-EL COMBI 40+ cochlear implant with complete insertion of the standard COMBI 40+ electrode array participated in the study. Acute speech tests were performed in seven electrode configurations with stimulation either distributed over the whole length of the cochlea or restricted to the apical, middle or basal regions. The test battery comprised tone, consonant, and vowel identification in quiet as well as a sentence recognition task in quiet and noise. RESULTS: While neither tone nor consonant identification depended crucially on the placement of the active electrodes, vowel identification and sentence recognition decreased significantly when the four apical electrodes were not stimulated.

Development of a Mandarin tone identification test: sensitivity index d' as a performance measure for individual tones.

OBJECTIVE: The aim of this study was to develop comprehensive test material for Mandarin tone identification in noise for a male and a female talker. Additionally, the sensitivity index d' as a measure for the listeners' performance to identify individual tones was evaluated. DESIGN: The study followed a prospective design. STUDY SAMPLE: The complete material comprises 72 loudness-balanced syllables in all 4 Mandarin tones. For a selection of 20 syllables, i.e. 80 test words, performance-versus-intensity functions were measured in spectrally matched noise for 16 normal-hearing participants. RESULTS: The average speech reception thresholds in noise were -12.9 dB for the male and -13.6 dB for the female talker recordings. The corresponding slopes were 8.6%/dB and 7.3%/dB. As a performance measure for individual tones, the proportion of correct responses to specific tones was substantially contaminated by response bias. The sensitivity index d', calculated according to detection theory, provided reasonable and unbiased performance versus intensity functions. CONCLUSIONS: The results firstly indicate that the material is homogenous enough for use as a speech test in clinical work and research. Secondly, to assess the discrimination performance for individual tones, d' values outperform the simple proportion of correct responses.

Temporal fine structure in cochlear implants: preliminary speech perception results in Cantonese-speaking implant users.

CONCLUSION: Acute comparisons between continuous interleaved sampling (CIS) and a temporal fine structure (TFS) coding strategy in Cantonese-speaking cochlear implant (CI) users did not reveal any significant differences in speech perception. Performance with the unfamiliar TFS coding strategy was on a par with CIS. Benefits of extended fine structure use observed in other studies should be investigated for tonal languages. OBJECTIVES: CIS-based stimulation strategies lack an explicit representation of fine structure, which is crucial for tonal language speech perception. The aim of this study was to assess speech recognition with a TFS coding strategy in Cantonese-speaking CI users with no prior fine structure experience. METHODS: The fine structure coding strategy encodes TFS on a few apical channels, while the remaining more basal channels carry CIS stimuli. Twelve MED-EL implantees and long-term CIS users participated in a study comparing recognition for Cantonese lexical tones and CHINT sentences between CIS and fine structure stimulation. RESULTS: Mean tone identification scores in 12 subjects were 59.2% with CIS and 59.2% with fine structure stimulation using 4 TFS channels, mean scores of CHINT sentences in 8 subjects were 54.2% with CIS and 55.9% with TFS stimulation. Differences between the two strategies were not significant for any speech test. Two additional versions of TFS strategy and pulse rates were tested in six subjects. No significant differences between strategies were found.

Results with a cochlear implant channel-picking strategy based on "Selected Groups".

A novel channel-picking strategy for cochlear implants (CIs) which considers the spatial distribution and the spectral relevance of the channels selected for stimulation is described. In the proposed strategy, the available channels are subdivided into groups, designated as "Selected Groups" (SG), and within each group, a specified number of active channels with the largest amplitudes are selected for stimulation. The hypothesis is that most of the spectral information that can be perceived by CI listeners is conveyed by taking the highest filter band outputs within a stimulation area represented by a group of neighboring channels. Two experiments were conducted in subjects with MED-EL implant systems, measuring recognition of sentences in speech-shaped noise. In experiment 1, the SG group size was varied from two to four while selecting one active channel per group and keeping the pulse phase durations constant. Results showed no significant difference in sentence recognition between continuous interleaved sampling and SG configurations up to a group size of three. In experiment 2, phase durations were doubled, using groups of two channels with one active channel each. This resulted in a reduction of pulse amplitudes by about 40%. Intelligibility of sentences in noise was unaffected, making a substantial reduction of implant supply voltages feasible. In all experiments, the stimulation frame rate was kept constant in order to avoid rate-change effects.