Recent results with the MED-EL COMBI 40+ cochlear implant and TEMPO+ behind-the-ear processor

Cochlear implantation is a viable treatment for patients with severe to profound hearing loss. We report the results of speech perception tests (numbers, monosyllables, and sentence tests) achieved with MED-EL's COMBI40+ (C40+) cochlear implant after 12 months of use. These findings, which were taken from a larger German study, were similar to those of other studies of the C40+ implant. We also compared the differences in speech perception observed with the CIS PRO+ body-worn speech processor and the newer TEMPO+ behind-the-ear speech processor. Although these results were similar with respect to most of the measured parameters, the TEMPO+ processor had a distinct advantage during tests in noise.     

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.     

Handling of the TEMPO+ behind-the-ear speech processor by MED-EL cochlear implant users

MED-EL launched its ear-level speech processor, the TEMPO+, in 1999. Studies have already demonstrated improved speech perception, sound quality and the ability to enjoy music with the TEMPO+ due to the new CIS+ speech-coding strategy. This study evaluated responses to 185 questionnaires about ease of handling and usage of the TEMPO+, opinion of and satisfaction with the TEMPO+ and its performance, as well as satisfaction with accessories. There was particular interest in seeing if the TEMPO+ was suitable for use with children. Results showed that MED-EL cochlear implant users felt comfortable manipulating the dials and switches, changing the battery pack, using external sources of input and with provided accessories. Overall, there was satisfaction with the TEMPO+. Notably, one third of respondents were under the age of 10. Results show the suitability of the TEMPO+ behind-the-ear speech processor for young children.     

Handling of the TEMPO+ behind-the-ear speech processor by MED-EL cochlear implant users

Abstract

MED-EL launched its ear-level speech processor, the TEMPO+, in 1999. Studies have already demonstrated improved speech perception, sound quality and the ability to enjoy music with the TEMPO+ due to the new CIS+ speech-coding strategy. This study evaluated responses to 185 questionnaires about ease of handling and usage of the TEMPO+, opinion of and satisfaction with the TEMPO+ and its performance, as well as satisfaction with accessories. There was particular interest in seeing if the TEMPO+ was suitable for use with children. Results showed that MED-EL cochlear implant users felt comfortable manipulating the dials and switches, changing the battery pack, using external sources of input and with provided accessories. Overall, there was satisfaction with the TEMPO+. Notably, one third of respondents were under the age of 10. Results show the suitability of the TEMPO+ behind-the-ear speech processor for young children.     

Handling of the MED-EL TEMPO+ ear-level speech processor by paediatric cochlear implant users and their parents

MED-EL launched the first ear-level speech processor offering a high-rate CIS+ strategy, the TEMPO+, in 1999. Studies have already demonstrated improved speech perception, sound quality and ability to enjoy music with the TEMPO+ due to the new CIS+ speech-coding strategy, when compared to the body-worn processor. In this study we evaluated responses from parents of young children about ease of handling and usage of the TEMPO+, and satisfaction with the TEMPO+ and its performance. Overall, 65 custom-designed questionnaires were analysed. The results showed that MED-EL cochlear implant users felt comfortable manipulating the dials and switches, changing the battery pack, using external sources of input and using the accessories provided. These results confirm the suitability of the TEMPO+ for infants and toddlers.     

Handling of the MED-EL TEMPO+ ear-level speech processor by paediatric cochlear implant users and their parents

MED-EL launched the first ear-level speech processor offering a high-rate CIS+ strategy, the TEMPO+, in 1999. Studies have already demonstrated improved speech perception, sound quality and ability to enjoy music with the TEMPO+ due to the new CIS+ speech-coding strategy, when compared to the body-worn processor. In this study we evaluated responses from parents of young children about ease of handling and usage of the TEMPO+, and satisfaction with the TEMPO+ and its performance. Overall, 65 custom-designed questionnaires were analysed. The results showed that MED-EL cochlear implant users felt comfortable manipulating the dials and switches, changing the battery pack, using external sources of input and using the accessories provided. These results confirm the suitability of the TEMPO+ for infants and toddlers.     

Clinical Trial Results with the MED-EL Fine Structure Processing Coding Strategy in Experienced Cochlear Implant Users

Objectives: To assess the subjective and objective performance of the new fine structure processing strategy (FSP) compared to the previous generation coding strategies CIS+ and HDCIS. Methods: Forty-six adults with a minimum of 6 months of cochlear implant experience were included. CIS+, HDCIS and FSP were compared in speech perception tests in noise, pitch scaling and questionnaires. The randomized tests were performed acutely (interval 1) and again after 3 months of FSP experience (interval 3). The subjective evaluation included questionnaire 1 at intervals 1 and 3, and questionnaire 2 at interval 2, 1 month after interval 1. Results: Comparison between FSP and CIS+ showed that FSP performed at least as well as CIS+ in all speech perception tests, and outperformed CIS+ in vowel and monosyllabic word discrimination. Comparison between FSP and HDCIS showed that both performed equally well in all speech perception tests. Pitch scaling showed that FSP performed at least as well as HDCIS. With FSP, sound quality was at least as good and often better than with HDCIS. Conclusions: Results indicate that FSP performs better than CIS+ in vowel and monosyllabic word understanding. Subjective evaluation demonstrates strong user preferences for FSP when listening to speech and music.     

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.     

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.     

Intra-and intersubject comparison of cochlear implant systems using the Esprit and the Tempo+ behind-the-ear speech processor: Comparacion intra e inter-personal de los sistemas de implante coclear utilizando los procesadores de lenguaje retroauriculares Esprit y Tempo+

A patient with bilateral profound deafness was implanted with a Nucleus CI24M cochlear implant (CI) and used an Esprit behind-the-ear (BTE) speech processor. Thirteen months later, the implant had to be removed because of a cholesteatoma. As the same electrode could not be reinserted, a Medel combi40s CI was implanted in the same ear, and the patient used a Tempo+ BTE processor. After 1 year of use of the Combi40s/Tempo+ system, speech recognition was better and was rated better subjectively than with the CI24M/Esprit system. Speech recognition and subjective ratings were also assessed for two matched groups of nine CI users each, using either an Esprit or a Tempo+ processor. On average, speech recognition scores were higher for the group of Tempo+ users, but the difference was not statistically significant. Users of the Esprit processors rated their device higher in terms of cosmetic appearance and comfort of wearing.

Sumario: Un paciente eon una sordera profunda bilateral fue implantado con un sistema coclear (IC) Nucleus CI24M, con el que utilizó un procesador de lenguaje retroauricular (BTE) Esprit. Trece meses después, el implante fue removido debido a un colesteatoma. Dado que el mismo electrodo no podia ser reinsertado, se implantó en el mismo oido un IC Med-El Combi 40+, con el que el paciente utilizó un procesador retroauricular (BTE) Tempo+. Luego de un año de uso del sistema Combi 40/Tempo+ el reconocimiento del habla fue considerado subjetivamente mejor con éste que con el sistema CI24M/Esprit. Se evaluó el reconocimiento del habla y la apreciación subjetiva en dos grupos de nueve usuarios de IC, utilizando procesadores Esprit o Tempo+. En promedio, los puntajes de reconocimiento del habla fueron más altos para el grupo de usuarios del Tempo+, pero la diferencia no fue estadisticamente significativa. Los usuarios del procesador Esprit calificaron su dispositivo como mejor en términos de apariencia y de comodidad de uso.     

Speech understanding with the CIS and the n-of-m strategy in the MED-EL COMBI 40+ system

Speech tests have been performed on 6 subjects for comparing the standard 12-channel continuous interleaved sampling (CIS) strategy (CIS12), the 7-channel CIS strategy (CIS7) and the 7-of-12 strategy in the MED-EL COMBI 40+ system. An ABAB experimental design was used whereby each strategy was reversed and replicated. Speech tests were performed in quiet (vowels, consonants, monosyllables, sentences) and noise (sentences). Results showed that for vowels, CIS12 is significantly superior to CIS7, for consonants and sentences CIS12, CIS7 and 7-of-12 performed equally well, and that for monosyllables 7-of-12 is significantly superior to both CIS12 and CIS7. In addition, 7-of-12 is superior to CIS7 by almost the same amount as CIS12, but in this case the difference is not significant. Further, all strategies have been found to be equally robust in noise with respect to sentence understanding. The differences between CIS12 and 7-of-12 on the one hand and CIS7 on the other hand may be attributed to decreased spectral resolution of the latter. The fact that - in contrast to what has been reported for the SPEAK strategy - 7-of-12 is equally robust in noise as the CIS strategies is explained by the use of higher stimulation rates, wider frequency bands and a higher percentage of channels stimulated in each cycle.     

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.     

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.     

Intra- and intersubject comparison of cochlear implant systems using the Esprit and the Tempo+ behind-the-ear speech processor

A patient with bilateral profound deafness was implanted with a Nucleus CI24M cochlear implant (CI) and used an Esprit behind-the-ear (BTE) speech processor. Thirteen months later, the implant had to be removed because of a cholesteatoma. As the same electrode could not be reinserted, a Medel combi40s CI was implanted in the same ear, and the patient used a Tempo+ BTE processor. After 1 year of use of the Combi40s/Tempo+ system, speech recognition was better and was rated better subjectively than with the CI24M/Esprit system. Speech recognition and subjective ratings were also assessed for two matched groups of nine CI users each, using either an Esprit or a Tempo+ processor. On average, speech recognition scores were higher for the group of Tempo+ users, but the difference was not statistically significant. Users of the Esprit processors rated their device higher in terms of cosmetic appearance and comfort of wearing.     

Recognition of speech presented at soft to loud levels by adult cochlear implant recipients of three cochlear implant systems

OBJECTIVE: The purpose of this study was to conduct a large-scale investigation with adult recipients of the Clarion, Med-El, and Nucleus cochlear implant systems to (1) determine average scores and ranges of performance for word and sentence stimuli presented at three intensity levels (70, 60, and 50 dB SPL); (2) provide information on the variability of scores for each subject by obtaining test-retest measures for all test conditions; and (3) further evaluate the potential use of lower speech presentation levels (i.e., 60 and/or 50 dB SPL) in cochlear implant candidacy assessment. DESIGN: Seventy-eight adult cochlear implant recipients, 26 with each of the three cochlear implant systems, participated in the study. To ensure that the data collected reflect the range of performance of adult recipients using recent technology for the three implant systems (Clarion HiFocus I or II, Med-El Combi 40+, Nucleus 24M or 24R), a composite range and distribution of consonant-nucleus-consonant (CNC) monosyllabic word scores was determined. Subjects using each device were selected to closely represent this range and distribution of CNC performance. During test sessions, subjects were administered the Hearing in Noise Test (HINT) sentence test and the CNC word test at three presentation levels (70, 60, and 50 dB SPL). HINT sentences also were administered at 60 dB SPL with a signal-to-noise ratio (SNR) of +8 dB. Warble tones were used to determine sound-field threshold levels from 250 to 4000 Hz. Test-retest measures were obtained for each of the speech recognition tests as well as for warble-tone sound-field thresholds. RESULTS: Cochlear implant recipients using the Clarion, Med-El, or Nucleus devices performed on average equally as well at 60 compared with 70 dB SPL when listening for words and sentences. Additionally, subjects had substantial open-set speech perception performance at the softer level of 50 dB SPL for the same stimuli; however, subjects' ability to understand speech was poorer when listening in noise to signals of greater intensity (60 dB SPL + 8 SNR) than when listening to signals presented at a soft presentation level (50 dB SPL) in quiet. A significant correlation was found between sound-field thresholds and speech recognition scores for presentation levels below 70 dB SPL. The results demonstrated a high test-retest reliability with cochlear implant users for these presentation levels and stimuli. Average sound-field thresholds were between 24 and 29 dB HL for frequencies of 250 to 4000 Hz, and results across sessions were essentially the same. CONCLUSIONS: Speech perception measures used with cochlear implant candidates and recipients should reflect the listening challenges that individuals encounter in natural communication situations. These data provide the basis for recommending new candidacy criteria based on speech recognition tests presented at 60 and/or 50 dB SPL, intensity levels that reflect real-life listening, rather than 70 dB SPL.     

Brazilian Portuguese speech material and its application in occupational audiology

Brazilian Portuguese speech test material consisting of nine monosyllabic 25-word lists was developed and digitally recorded on one channel of a compact disk with a speech-weighted modulated broadband noise on the other channel. Speech recognition functions in quiet and in noise, with word and phoneme scores, were obtained, and normative speech recognition data were standardized by determination of the psychometric function in 21 normally-hearing volunteers in quiet, and in 30 normally-hearing subjects in noise. The homogeneity of the nine lists was investigated in phoneme recognition data with 30 normally-hearing subjects. Speech recognition functions in quiet and in noise, with word and phoneme scores, were obtained in 65 noise-exposed workers. These results were very close to normative data, when tested in quiet, but significantly worse when tested in noise. It is concluded that the speech test material can be useful for estimating the communication performance of noise-exposed workers.     

A multicentre clinical evaluation of paediatric cochlear implant users upgrading to the Nucleus® 6 system

ObjectivesThe aim of this study was to investigate whether experienced paediatric cochlear implant users could show benefits to speech perception outcomes from the introduction of noise reduction and automated scene classification technologies as implemented in the Nucleus^® 6 sound processor. Previous research with adult cochlear implant users had shown significant improvements in speech intelligibility for listening in noisy conditions and good user acceptance for upgrading to the Nucleus 6 processor. In adults, these improvements for listening in noise were primarily attributed to the use of a range of new input processing technologies including noise reduction, as well as introduction of automatic scene classification technology.MethodsExperienced paediatric cochlear implant users (n = 25) were recruited from four clinics located in three countries. Research participants were evaluated on three occasions, an initial session using their Nucleus 5 sound processor; a second session in which participants used the Nucleus 6 processor programmed with the same technologies as were used in their Nucleus 5 sound processor; and a final session in which participants used the Nucleus 6 processor programmed with the default technologies including automatic scene classification (SCAN) which automatically selects the microphone directionality, noise reduction (SNR-NR), and wind noise reduction (WNR) technologies. Prior to both the second and third evaluations, research participants had approximately two weeks take-home experience with the new system. Speech perception performances on monosyllabic word tests presented in quiet and in noise, and a sentence test presented in noise, were compared across the three processor conditions. Acceptance of the Nucleus 6 default settings was assessed in a final session.ResultsNo group mean difference in performance was found for monosyllabic words in quiet. A significant improvement in speech perception was found for both monosyllabic words and sentences in noise with the default Nucleus 6 program condition as compared with the Nucleus 5 condition. No acceptance issues were noted for any of the children.ConclusionsExperienced paediatric cochlear implant users showed a significant improvement in speech perception in listening in noise when upgraded to the Nucleus 6 sound processor primarily due to the introduction of a noise reduction technology, and all children accepted the default program. These findings suggest that school-aged children may benefit from upgrading to the Nucleus 6 sound processor using the default program.     

Speech understanding in noise with a Med-El COMBI 40+ cochlear implant using reduced channel sets

OBJECTIVE: The objective of the investigation described in this paper was the determination of the number of (widely spaced) active electrodes needed for users of a COMBI 40+ cochlear implant to achieve asymptotic performance in the recognition of speech against a background of wideband noise. DESIGN: This study measured the performance in speech tests of patients using the Med-El implementation of continuous interleaved sampling with widely spaced electrode pair subsets of 2, 3, 4, 6, 8, and 10 out of a possible maximum of 12. An eight-vowel test, a 16-consonant test, and BKB sentences were presented against a background of pink noise. Additionally, AB monosyllabic words were presented both in quiet and in noise to processors with 6, 8, and 11 widely spaced electrodes. 11 subjects participated in the study. RESULTS: Using moderate signal-to-noise ratios, for these patients the curve relating percentage score to increasing numbers of active channels approached an asymptote before the 10-channel data point was reached. Asymptotic performance was achieved using four channels for consonants, and eight channels for sentences. Understanding of monosyllabic words reached a maximum value at a similar number of channels for both quiet conditions and against a background of pink noise, and the mean increase in test score between 6 and 11 channels was only 7%. CONCLUSIONS: These results are similar to those of previous experiments carried out in quiet listening conditions. The data suggest that 12 frequency channels (the number implemented by the COMBI 40+ cochlear implant) are more than adequate for users to achieve asymptotic performance levels in clinical speech tests applied in the presence of wideband noise at moderate signal-to-noise ratios.     

Speech understanding in quiet and noise in bilateral users of the MED-EL COMBI 40/40+ cochlear implant system

OBJECTIVE: The purpose of the study was to investigate speech understanding in quiet and noise in subjects bilaterally implanted with multi-channel cochlear implants. DESIGN: Nine adults bilaterally implanted with MED-EL implants were included in the study. The subjects were tested in three conditions: with both implants, with the right implant only, and with the left implant only. Speech tests included monosyllables in quiet and sentences in noise (10 dB signal to noise ratio). Speech was presented from the front, and noise was presented from either 90 degrees or 270 degrees azimuth. RESULTS: All subjects reported benefit from bilateral stimulation. Speech scores for all subjects were higher with bilateral than with unilateral stimulation. The average score across subjects for sentence understanding was 31.1 percentage points higher with both cochlear implants compared with the cochlear implant ipsilateral to the noise, and 10.7 percentage points higher with both cochlear implants compared with the cochlear implant contralateral to the noise. The average score for recognition of monosyllabic words was 18.7 percentage points higher with both cochlear implants than with one cochlear implant. All of these differences in average scores were significant at the 5% level. CONCLUSIONS: Bilateral cochlear implantation provides a significant benefit in speech understanding in both quiet and noise.     

Effects of stimulation rate on speech recognition with cochlear implants

Phoneme and speech recognition were measured as a function of stimulation pulse rate in 12 listeners with three types of cochlear implants. Identification of consonants and vowels and recognition of words and sentences were measured in 5 Clarion C1 subjects fit with continuous interleaved sampling (CIS) processors having 4 or 8 electrodes, 4 Nucleus 24 subjects fit with CIS processors having 4, 8, 12 or 16 electrodes and 3 Clarion C2 subjects fit with CIS processors with 4, 8, 12 and 16 electrodes. Stimulation rates ranged from 200 to more than 5000 Hz per electrode, depending on the device, number of electrodes used and stimulation strategy. Listeners were also tested on the same materials with their original processor prior to receiving the experimental processors. All testing was done in quiet listening conditions with essentially no practice with the experimental processor prior to data collection. Listeners scored the highest with their original processor. Little difference in speech understanding was observed for listener scores with processors using different stimulation rates. Speech recognition was significantly poorer only at the lowest stimulation rate and at high rates that used noninterleaved pulses. Speech recognition was similar for processors using 8, 12 or 16 electrodes. Only 4-electrode processors produced a significantly poorer performance. These results suggest that patients with present commercial implants are not able to make full use of the number of channels of spectral information delivered by the present speech processors. In addition, the results show no significant change in performance as a function of stimulation rate, suggesting that high stimulation rates do not result in improved access to temporal cues in speech, at least under quiet listening conditions.