Fine Structure Processing improves speech perception as well as objective and subjective benefits in pediatric MED-EL COMBI 40+ users

Objectives

Presently, there are only few studies examining the benefits of fine structure information in coding strategies. Against this background, this study aims to assess the objective and subjective performance of children experienced with the C40+ cochlear implant using the CIS+ coding strategy who were upgraded to the OPUS 2 processor using FSP and HDCIS.

Methods

In this prospective study, 60 children with more than 3.5 years of experience with the C40+ cochlear implant were upgraded to the OPUS 2 processor and fit and tested with HDCIS (Interval I). After 3 months of experience with HDCIS, they were fit with the FSP coding strategy (Interval II) and tested with all strategies (FSP, HDCIS, CIS+). After an additional 3-4 months, they were assessed on all three strategies and asked to choose their take-home strategy (Interval III). The children were tested using the Adaptive Auditory Speech Test which measures speech reception threshold (SRT) in quiet and noise at each test interval. The children were also asked to rate on a Visual Analogue Scale their satisfaction and coding strategy preference when listening to speech and a pop song. However, since not all tests could be performed at one single visit, some children were not able complete all tests at all intervals.

Results

At the study endpoint, speech in quiet showed a significant difference in SRT of 1.0 dB between FSP and HDCIS, with FSP performing better. FSP proved a better strategy compared with CIS+, showing lower SRT results of 5.2 dB. Speech in noise tests showed FSP to be significantly better than CIS+ by 0.7 dB, and HDCIS to be significantly better than CIS+ by 0.8 dB. Both satisfaction and coding strategy preference ratings also revealed that FSP and HDCIS strategies were better than CIS+ strategy when listening to speech and music. FSP was better than HDCIS when listening to speech.

Conclusions

This study demonstrates that long-term pediatric users of the COMBI 40+ are able to upgrade to a newer processor and coding strategy without compromising their listening performance and even improving their performance with FSP after a short time of experience.     

Comparison of the TEMPO+ ear-level speech processor and the cis pro+ body-worn processor in adult MED-EL cochlear implant users

A study was conducted to compare the new MED-EL TEMPO+ ear-level speech processor with the CIS PRO+ body-worn processor in the COMBI 40/COMBI 40+ implant system. Speech tests were performed in 46 experienced subjects in two test sessions approximately 4 weeks apart. Subjects were switched over from the CIS PRO+ to the TEMPO+ in the first session and used only the TEMPO+ in the time between the two sessions. Speech tests included monosyllabic word tests and sentence tests via the telephone. An adaptive noise method was used to adjust each subject's scores to approximately 50%. Additionally, subjects had to complete a questionnaire based on their 4 weeks of experience with the TEMPO+. The speech test results showed a statistically significant improvement in the monosyllabic word scores with the TEMPO+. In addition, in the second session, subjects showed a significant improvement when using the telephone with the TEMPO+, indicating some learning in this task. In the questionnaire, the vast majority of subjects found that the TEMPO+ allows equal or better speech understanding and rated the sound quality of the TEMPO+ higher. All these objective and subjective results indicate the superiority of the TEMPO+ and are mainly attributed to a new coding strategy called CIS+ and its implementation in the TEMPO+. In other words, based on the results of this study, it appears that after switching over from the CIS PRO+ to the TEMPO+, subjects are able to maintain or even improve their own speech understanding capability.     

A comparison of Tactaid II+ and Tactaid 7 use by adults with a profound hearing impairment

OBJECTIVE: To evaluate and compare use of the Tactaid II+ and the Tactaid 7, in terms of speech perception, by adults with a hearing impairment. DESIGN: Eight adults used one device daily for approximately 10 wk and attended seven training sessions. Performance was measured with tests of phonetic contrast perception, closed-set vowel and consonant identification, word and phoneme recognition in monosyllabic word lists, word recognition in sentences and speechtracking rate. A questionnaire was also administered. The protocol was repeated with the alternative device. RESULTS: With each device, the group discriminated most phonetic contrasts at better-than-chance levels and demonstrated somewhat enhanced visual or auditory-visual perception when measured in terms of vowel identification, monosyllabic word recognition and speechtracking rate. An increase in speechtracking rate was also demonstrated for some individuals. Subjects generally reported little subjective improvement in speech perception and production, but were satisfied with the physical attributes of each device. Five of six subjects preferred the Tactaid 7. CONCLUSIONS: The Tactaid II+ and the Tactaid 7 provided suprasegmental and segmental information, enabling the group to discriminate phonetic contrasts and improve their perception of some speech materials. No consistent advantage was found for either device, thought most subjects preferred the Tactaid 7. Alternatives likely to provide a greater benefit to communication should be considered before a Tactaid fitting.     

Fine structure processing improves telephone speech perception in cochlear implant users

The objective of this study was to compare telephone speech perception and subjective preferences in cochlear implant users with two different speech-processing strategies: high-definition continuous interleaved sampling (HDCIS) and fine structure processing (FSP). A randomized double-blind study was designed for intra-individual comparison of HDCIS and FSP. Twenty-five post-lingually deafened patients with either the PulsarCI¹⁰⁰ or SonataTI¹⁰⁰ and Opus2 acoustic processor were tested consecutively with both coding strategies, assigned in a random order. Disyllabic word speech perception was tested 6 weeks after each fitting under the following conditions: landline use with (LWN) and without (LWoN) background noise, mobile use with (MWN), and without (MWoN) background noise and mobile use with a Bluetooth magnetic field transmitter necklace (MB). Changes in health-related quality of life (QoL) were assessed using the Glasgow Benefit Inventory (GBI) and Faber’s questionnaire. Personal preferences between strategies were surveyed upon completion of the study. All subjects included in this study performed better with FSP in the landline tests. There was an improvement of 11.5 % in LWN use (p = 0.014; CI 95 % = 3–20 %) and 10 % in LWoN use (p = 0.001; CI 95 % = 5–15 %). MWoN showed an improvement of 6.3 % with FSP (p = 0.03; CI 95 % = 0–13 %). MB tests showed an improvement of 11 % with FSP (p < 0.05; CI 95 % = 1.5–22 %). Quality of life was significantly better using FSP. Eighty-four percent of participants preferred FSP. The FSP speech coding strategy improved the speech recognition of cochlear implant users when using the telephone compared to HDCIS. Cochlear implantation with FSP coding improved QoL.     

Comparison of two cochlear implant coding strategies on speech perception

Objective: Assess whether differences in speech perception are observed after exclusive listening experience with high-definition continuous interleaved sampling (HDCIS) versus fine structure processing (FSP) coding strategies.

Methods: Subjects were randomly assigned at initial activation of the external speech processor to receive the HDCIS or FSP coding strategy. Frequency filter assignments were consistent across subjects. The speech perception test battery included CNC words in quiet, HINT sentences in quiet and steady noise (+10?dB SNR), AzBio sentences in quiet and a 10-talker babble (+10?dB SNR), and BKB-SIN. Assessment intervals included 1, 3, and 6 months post-activation.

Results: Data from 22 subjects (11 with HDCIS and 11 with FSP) were assessed over time. Speech perception performance was not significantly different between groups.

Discussion: Speech perception performance was not significantly different after 6 months of listening experience with the HDCIS or FSP coding strategy.     

Speech and music perception with the new fine structure speech coding strategy: preliminary results

CONCLUSIONS: Taking into account the excellent results with significant improvements in the speech tests and the very high satisfaction of the patients using the new strategy, this first implementation of a fine structure strategy could offer a new quality of hearing with cochlear implants (CIs). OBJECTIVE: This study consisted of an intra-individual comparison of speech recognition, music perception and patient preference when subjects used two different speech coding strategies with a MedEl Pulsar CI: continuous interleaved sampling (CIS) and the new fine structure processing (FSP) strategy. In contrast to envelope-based strategies, the FSP strategy also delivers subtle pitch and timing differences of sound to the user and is thereby supposed to enhance speech perception in noise and increase the quality of music perception. PATIENTS AND METHODS: This was a prospective study assessing performance with two different speech coding strategies. The setting was a CI programme at an academic tertiary referral centre. Fourteen post-lingually deaf patients using a MedEl Pulsar CI with a mean CI experience of 0.98 years were supplied with the new FSP speech coding strategy. Subjects consecutively used the two different speech coding strategies. Speech and music tests were performed with the previously fitted CIS strategy, immediately after fitting with the new FSP strategy and 4, 8 and 12 weeks later. The main outcome measures were individual performance and subjective assessment of two different speech processors. RESULTS: Speech and music test scores improved statistically significantly after conversion from CIS to FSP strategy. Twelve of 14 patients preferred the new FSP speech processing strategy over the CIS strategy.     

言语编码策略升级对成年人工耳蜗使用者听觉效果影响的研究

目的　探讨言语编码策略升级对有经验人工耳蜗使用者听觉效果的影响趋势,以期为临床制定有效的人工耳蜗言语编码策略升级方案提供参考依据。方法　采用噪声下汉语普通话声调识别测试、普通话噪声下言语识别测试以及自行编制的声音质量自评问卷,对13例有经验成年人工耳蜗使用者言语编码策略升级后的声调识别能力、短句分辨能力以及声音质量和聆听感受进行3个月连续观测。以使用日常言语编码策略（即CIS+策略）的测试结果为参考值,以新言语编码策略（即精细结构编码策略）的测试 结果为目标值,分析言语编码策略升级对成年人工耳蜗使用者听觉效果的影响。结果　①声调识别能力：各测试阶段两种编码策略的声调识别测试成绩无显著差异,随着精细结构编码策略使用经验增加,测试成绩呈明显改善趋势[F（3,36）=5.201,P =0.004];②短句分辨能力：各测试阶段两种编码策略的言语识别测试成绩无显著差异,随精细结构编码策略使用经验增加,测试成绩略有提高[F（3,36）=2.450,P =0.079];③声音质量自评：更换言语编码策略对本组受试者的声音质量和聆听感受无不利影响（P =0.083）。随着精细结构编码策略使用经验增加,受试者认为声音质量更“饱满、丰富”、聆听感受更“容易、轻松”。结论　言语编程策略升级未对有经验人工耳蜗使用者的言语识别能力造成不良影响且存在潜在的改善作用。在临床工作中可参考患者主观意愿确定是否升级言语编程策略。     

Speech and music perception with the new fine structure speech coding strategy: preliminary results

Conclusions. Taking into account the excellent results with significant improvements in the speech tests and the very high satisfaction of the patients using the new strategy, this first implementation of a fine structure strategy could offer a new quality of hearing with cochlear implants (CIs). Objective. This study consisted of an intra-individual comparison of speech recognition, music perception and patient preference when subjects used two different speech coding strategies with a MedEl Pulsar CI: continuous interleaved sampling (CIS) and the new fine structure processing (FSP) strategy. In contrast to envelope-based strategies, the FSP strategy also delivers subtle pitch and timing differences of sound to the user and is thereby supposed to enhance speech perception in noise and increase the quality of music perception. Patients and methods. This was a prospective study assessing performance with two different speech coding strategies. The setting was a CI programme at an academic tertiary referral centre. Fourteen post-lingually deaf patients using a MedEl Pulsar CI with a mean CI experience of 0.98 years were supplied with the new FSP speech coding strategy. Subjects consecutively used the two different speech coding strategies. Speech and music tests were performed with the previously fitted CIS strategy, immediately after fitting with the new FSP strategy and 4, 8 and 12 weeks later. The main outcome measures were individual performance and subjective assessment of two different speech processors. Results. Speech and music test scores improved statistically significantly after conversion from CIS to FSP strategy. Twelve of 14 patients preferred the new FSP speech processing strategy over the CIS strategy.     

Speech recognition outcomes in Mandarin-speaking cochlear implant users with fine structure processing

Conclusion: Mandarin-speaking adults can use the Fine Structure Processing (FSP) coding strategy as well as the Continuous Interleaved Sampling (CIS+) coding strategy. No loss in performance was observed after switch-over. Tone identification improves over time with the FSP coding strategy, which is of benefit to tonal-language users. After some time, fine structure was preferred.

Objective: This study aimed to determine speech perception, tone perception, and the subjective preferences of Mandarin-speaking adults who received the FSP coding strategy, at upgrade from the CIS?+?coding strategy.

Methods: Thirteen Mandarin-speaking subjects were tested at switch-over from CIS?+?to the FSP coding strategy ～1-month after switch-over, 2-months after switch-over, and 3-months after switch-over with the Mandarin Hearing in Noise Test (M-HINT), the Mandarin Tone Identification in Noise Test (M-TINT), and a visual analogue scale assessing Sound and Speech Assessment (SSA).

Results: There were no significant differences in the M-HINT between presentation levels (62?dB SPL vs 65?dB SPL), over time, nor when compared to the CIS?+?coding strategy. Tone perception improved significantly over time with the FSP coding strategy. Subjects rated the FSP coding strategy with the OPUS 2 as significantly more ‘full’ and ‘rich’ than with the CIS?+?coding strategy after 3-months.     

Variables affecting implant performance in children

This study examined the variables that contribute to the large individual differences in the speech perception skills of children with the Nucleus multichannel cochlear implant. Sixty-one children were tested on four measures of speech perception: two tests of closed-set word recognition, one test of open-set recognition of phrases, and one open-set monosyllabic word test, scored on the basis of the percentage of phonemes as well as words identified correctly. The results of a series of multiple regression analyses revealed that the variables of processor type, duration of deafness, communication mode, age at onset of deafness, length of implant use, and age implanted accounted for roughly 35% of the variance on two tests of closed-set word recognition, and 40% of the variance on measures that assessed recognition of words or phomenes in an open set. Length of implant use accounted for the most variance on all of the speech perception measures.     

Speech perception test for Arabic-speaking children

The high incidence of hearing impairment in the Arabic-speaking population in Israel, as well as the use of advanced aural rehabilitation devices, motivated the development of Arabic speech assessment tests for this population. The purpose of this paper is twofold. The first goal is to describe features that are unique to the Arabic language and that need to be considered when developing such speech tests. These include Arabic diglossia (i.e., the sharp dichotomy between Literary and Colloquial Arabic), emphatization, and a simple vowel system. The second goal is to describe a new analytic speech test that assesses the perception of significant phonological contrasts in the Colloquial Arabic variety used in Israel. The perception of voicing, place, and manner of articulation, in both initial and final word positions, was tested at four sensation levels in 10 normally-hearing subjects using a binary forced-choice paradigm. Results show a relationship between percent correct and presentation level that is in keeping with articulation curves obtained with Saudi Arabic and English monosyllabic words. Furthermore, different contrasts yielded different articulation curves: emphatization was the easiest to perceive whereas place of articulation was the most difficult. The results can be explained by the specific acoustical features of Arabic.     

Performance of patients using different cochlear implant systems: effects of input dynamic range

OBJECTIVE: To determine, for patients who had identical levels of performance on a monosyllabic word test presented in quiet, whether device differences would affect performance when tested with other materials and in other test conditions. DESIGN: For Experiment 1, from a test population of 76 patients, three groups (N = 13 in each group) were created. Patients in the first group used the CII Bionic Ear behind-the-ear (BTE) speech processor, patients in the second group used the Esprit3G BTE speech processor, and patients in the third group used the Tempo+ BTE speech processor. The patients in each group were matched on (i) monosyllabic word scores in quiet, (ii) age at testing, (iii) duration of deafness, and (iv) experience with their device. Performance of the three groups was compared on a battery of tests of speech understanding, voice discrimination, and melody recognition. In Experiments 2 (N = 10) and 3 (N = 10) the effects of increasing input dynamic range in the 3G and CII devices, respectively, was assessed with sentence material presented at conversational levels in quiet, conversational levels in noise, and soft levels in quiet. RESULTS: Experiment 1 revealed that patients fit with the CII processor achieved higher scores than Esprit3G and Tempo+ patients on tests of vowel recognition. CII and Tempo+ patients achieved higher scores than Esprit3G patients on difficult sentence material presented in noise at +10 and +5 dB SNR. CII patients achieved higher scores than Esprit3G patients on difficult sentence material presented at a soft level (54 dB SPL). Experiment 2 revealed that increasing input dynamic range in the Esprit3G device had (i) no effect at conversational levels in quiet, (ii) degraded performance in noise, and (iii) improved performance at soft levels. Experiment 3 revealed that increasing input dynamic range in the CII device improved performance in all conditions. CONCLUSIONS: Differences in implant design can affect patient performance, especially in difficult listening situations. Input dynamic range and the method by which compression is implemented appear to be the major factors that account for our results.     

Comparison of the body-worn CIS-PRO+ and the behind-the-ear-worn TEMPO+ cochlear implant systems in Finnish-speaking adult CI users: any differences in results with experienced listeners?

Conclusion. The results indicate that the need for upgrading the processor and/or speech coding strategy should be considered individually, if the processor and coding strategy are functioning properly and a good level of speech perception has been achieved. Objectives. Our aim was to study the intra-individual differences of the body-worn CIS-PRO+ and the behind-the-ear-worn TEMPO+ cochlear implant systems used in the MED-EL Combi40/Combi40+ implants. Subjects and methods. The hearing level, sentence, word and phoneme recognition of eight adult subjects were determined in an ABA study design. Additionally, a self-assessment questionnaire was used. Mean scores and 95% confidence intervals, and individual scores were analysed. Results. The subjects tended to score slightly better on word and phoneme recognition with CIS-PRO+ and CIS strategy than with TEMPO+ and CIS+, but there were no statistically significant differences. Subjectively the participants ranked speech perception and discussion in noise to be slightly easier with TEMPO+ and CIS+. Six of the eight subjects preferred TEMPO+ and CIS+ and two of eight preferred CIS-PRO+ with CIS or number-of-maxima.     

Comparison of speech processing strategies used in the Clarion implant processor

OBJECTIVE: To evaluate the performance of the various speech processing strategies supported by the Clarion S-Series implant processor. DESIGN: Five different speech-processing strategies [the Continuous Interleaved Sampler (CIS), the Simultaneous Analog Stimulation (SAS), the Paired Pulsatile Sampler (PPS), the Quadruple Pulsatile Sampler (QPS) and the hybrid (HYB) strategies] were implemented on the Clarion Research Interface platform. These speech-processing strategies varied in the degree of electrode simultaneity, with the SAS strategy being fully simultaneous (all electrodes are stimulated at the same time), the PPS and QPS strategies being partially simultaneous and the CIS strategy being completely sequential. In the hybrid strategy, some electrodes were stimulated using SAS, and some were stimulated using CIS. Nine Clarion CIS users were fitted with the above speech processing strategies and tested on vowel, consonant and word recognition in quiet. RESULTS: There were no statistically significant differences in the mean group performance between the CIS and SAS strategies on vowel and sentence recognition. A statistically significant difference was found only on consonant recognition. Individual results, however, indicated that most subjects performed worse with the SAS strategy compared with the CIS strategy on all tests. About 33% of the cochlear implant users benefited from the PPS and QPS strategies on consonant and word recognition. CONCLUSIONS: If temporal information were the primary factor in speech recognition with cochlear implants then SAS should consistently produce higher speech recognition scores than CIS. That was not the case, however, because most CIS users performed significantly worse with the SAS strategy on all speech tests. Hence, there seems to be a trade-off between improving the temporal resolution with an increasing number of simultaneous channels and introducing distortions from electrical-field interactions. Performance for some CI users improved when the number of simultaneous channels increased to two (PPS strategy) and four (QPS strategy). The improvement with the PPS and QPS strategies must be due to the higher rates of stimulation. The above results suggest that CIS users are less likely to benefit with the SAS strategy, and they are more likely to benefit from the PPS and QPS strategies, which provide higher rates of stimulation with small probability of channel interaction.     

Connexin-associated deafness and speech perception outcome of cochlear implantation

OBJECTIVE: To compare performance after cochlear implantation in children with mutations in connexin (Cx) 26 (GJB2) or Cx30 (GJB6) and children with deafness of unknown etiology. DESIGN: Genetic analysis and speech perception evaluation was performed in the children with and without Cx mutations who had undergone cochlear implantation. Speech perception performance was retrospectively analyzed 6, 12, 24, 36, and 48 months after implantation. Test material was selected according to the child's age and cognitive and language abilities. SETTING: The study took place at speech and hearing and genetic centers of a hospital in the central part of Israel and the genetics departments of 3 additional centrally located hospitals. PATIENTS: A total of 30 children who had undergone cochlear implantation were selected for the study, with control patients matched according to age at implantation, duration of implant use, and mode of communication. There was no evidence for additional disabilities or handicaps in either group. MAIN OUTCOME MEASURES: Speech perception measurements included a questionnaire, as well as closed and open-set tests. RESULTS: Overall, the 2 groups showed significant improvement in speech perception results after implantation. Four years after implantation, both groups achieved mean open-set speech perception scores of approximately 60%, 75%, and 90% for monosyllabic, 2 syllables, and words in sentences tests, respectively. CONCLUSIONS: There were no apparent differences in speech perception performance after implantation between the children with Cx mutations and children with deafness of unknown etiology. These data have important implications as a prognostic indicator when counseling candidates for cochlear implantation.     

Within-patient longitudinal speech reception measures with continuous interleaved sampling processors for ineraid implanted subjects.

OBJECTIVE: To assess within-subject changes in speech reception over time in a group of Ineraid subjects fitted with continuous interleaved sampling (CIS) wearable processors fabricated in Geneva. To compare asymptotic performance between CIS and Ineraid processors for the same subjects. DESIGN: Twelve patients, all users of the 4-channel Ineraid cochlear implant system for several years and with no previous experience of CIS processors in daily life, were equipped with Geneva Wearable Processors programmed to implement a high-rate CIS sound processing strategy using four to six channels. Their speech reception performance with CIS processors was monitored over a period of 1 yr with consonant and vowel identification tests. For comparison, speech reception performance also was measured with Ineraid processors before switching to CIS and after 6 mo of non-use of Ineraid processors. RESULTS: At fitting, CIS processors produced significantly better consonant identification but no better vowel identification. Subsequently, consonant and vowel scores with CIS processors improved progressively to asymptote after 6 mo of daily use. At 6 mo and beyond, performance with CIS processors was significantly superior to that obtained with Ineraid processors on both consonant and vowel identification tests. Control tests made with Ineraid processors after 6 mo of non-use of the device yielded results that were indistinguishable from those obtained before the study. CONCLUSIONS: The full potential of the CIS strategy is not revealed at fitting. Accumulation of daily experience provides significant improvements, asymptotic performance being reached after about 4 to 6 mo of use. All Ineraid users might greatly benefit from CIS processors.     

Monosyllable speech perception of Japanese hearing aid users with prelingual hearing loss: implications for surgical indication of cochlear implant

OBJECTIVE: The monosyllable speech perception ability after years of educational intervention was compared between prelingually deafened pediatric hearing aid users and their cochlear implant counterparts. DESIGN: An open-set monosyllabic speech perception test was conducted on all subjects. The test required subjects to indicate a corresponding Japanese character to that spoken by the examiner. Fifty-two subjects with prelingual hearing impairment (47 hearing aid users and 5 cochlear implant users) were examined. RESULTS: Hearing aid users with average pure-tone thresholds less than 90 dB HL demonstrated generally better monosyllable perception than 70%, which was equivalent or better performance than that of the cochlear implant group. Widely dispersed speech perception was observed within the 90-99 dB HL hearing-aid user group with most subjects demonstrating less than 50% speech perception. In the cluster of >100 dB HL, few cases demonstrated more than 50% in speech perception. The perception ability of the vowel part of each mora within the cochlear implant group was 100% and corresponding to that of hearing aid users with moderate and severe hearing loss. CONCLUSION: Hearing ability among cochlear implant users can be comparable with that of hearing aid users with average unaided pure-tone thresholds of 90 dB HL, after monosyllabic speech perception testing was performed.     

The effects of an acquired profound hearing loss on speech production. A case study

Three parallel studies conducted with an early adolescent male subject deafened by meningitis at age 11 are reported. Study 1 plotted phonetic errors in spontaneous and read speech, long-term average spectra and vowel formant frequencies. Study 2 measured the subject's speech intelligibility using monosyllabic word lists. Study 3 involved normal hearer 's ratings of the subject's speech 2 months and 30 months after the onset of deafness. The results obtained revealed a deterioration in both speech intelligibility and quality.     

Modification of speech encoding process of single channel cochlear implant utilizing digital delay circuit

Speech perception by single channel cochlear implant can be improved to some extent by modifying the encoding process of the speech signals. The principle of our encoding strategy is to present speech signals with appropriate delay time for lower frequency components of the speech sound, while without delay for higher frequency components. This is based on a cochlear physiology that higher frequency sounds are perceived earlier than lower frequency sounds, since the former is perceived at the basal turn and the latter at the apical turn. The following tests were performed without the aid of lip reading in the two patients implanted with a single channel cochlear implant of 3M-House design. Lower frequency components of the speech signals were digitally delayed with a Sony SDP-777 ES surround processor. The results indicated that the optimal delay time for identification of /i/, /e/ and /u/ needed longer delay time, while that of /a/ and /o/ need shorter delay time, corresponding to the difference between the first and second formant of each vowel. Comparison of vowel perception with and without delay coding showed that vowel identification with delay coding was superior to that without it; 30% vs. 16% in case 1, and 48% vs. 30% in case 2.     

Performance of compressed analogue (CA) and continuous interleaved sampling (CIS) coding strategies for cochlear implants in quiet and noise

Speech understanding with compressed analogue (CA) and continuous interleaved sampling (CIS) coding strategies for cochlear implants was compared in quiet and in noise at signal-to-noise ratios (SNRs) of 15, 10 and 5 dB. The speech recognition of three experienced users of the Ineraid cochlear implant (CA coding strategy) was assessed using a set of sentence, vowel and consonant tests. Three weeks after the fitting of a CIS processor, the tests were repeated with the new device. Speech recognition scores for the sentence and consonant tests tended to be higher with the CIS processor in no or little noise, but lower in the test situations with less favourable SNRs, when compared to the CA processor (average score differences for the consonant test: +7.8% correct at 15 dB SNR; -6.8% correct at 5 dB SNR; p = 0.05). Results for the vowel test were slightly lower on average for the CIS processing strategy at all SNRs. A possible explanation for the differences in performance between CIS and CA in the consonant and sentence tests at different SNRs is the generally higher free-field threshold associated with the CA coding strategy, which may act as a single-channel noise suppression.