An investigation into the effect of limiting the frequency bandwidth of speech on speech recognition in adult cochlear implant users

The purpose of this study was to investigate the effect of the limited-frequency bandwidth employed by telephones (300-3400 Hz) on speech recognition in adult cochlear implant users. The Four Alternative Auditory Feature (FAAF) test was used in four conditions: unfiltered and in three filtered conditions of 300-4500 Hz, 300-3400 Hz and 300-2500 Hz. Ten subjects implanted with the Nucleus CI24M device and 10 normal-hearing listeners were assessed to examine differences between word discrimination scores in each condition. Scores obtained from the 300-3400-Hz and 300-2500-Hz filtered conditions were significantly worse than those with unfiltered speech for the cochlear implant subjects, decreasing by 17.7% and 21.4%, respectively, from scores with unfiltered speech. By contrast, the normal-hearing listeners did not experience difficulties in discriminating between words in any of the conditions. Analysis of the word errors demonstrated that the reduction in implant subject scores with bandwidth arose from errors in place of articulation. Filtering speech in this way has a significant effect on speech recognition for cochlear implant subjects but not normal-hearing listeners. Hence, the limitations of the normal telephone bandwidth can be expected to have a negative effect on speech recognition for cochlear implant users using the telephone.     

Mandarin Chinese speech recognition by pediatric cochlear implant users

Objectives

Because of difficulties associated with pediatric speech testing, most pediatric cochlear implant (CI) speech studies necessarily involve basic and simple perceptual tasks. There are relatively few studies regarding Mandarin-speaking pediatric CI users’ perception of more difficult speech materials (e.g., words and sentences produced by multiple talkers). Difficult speech materials and tests necessarily require older pediatric CI users, who may have different etiologies of hearing loss, duration of deafness, CI experience. The present study investigated how pediatric CI patient demographics influence speech recognition performance with relatively difficult test materials and methods.

Methods

In this study, open-set recognition of multi-talker (two males and two females) Mandarin Chinese disyllables and sentences were measured in 37 Mandarin-speaking pediatric CI users. Subjects were grouped according to etiology of deafness and previous acoustic hearing experience. Group 1 subjects were all congenitally deafened with little-to-no acoustic hearing experience. Group 2 subjects were not congenitally deafened and had substantial acoustic hearing experience prior to implantation. Multiple linear regression analyses were performed within each group using subject demographics such as age at implantation and age at testing.

Results

Pediatric CI performance was generally quite good. For Group 1, mean performance was 82.3% correct for disyllables and 82.8% correct for sentences. For Group 2, mean performance was 76.6% correct for disyllables and 84.4% correct for sentences. For Group 1, multiple linear regression analyses showed that age at implantation predicted disyllable recognition, and that age at implantation and age at testing predicted sentence recognition. For Group 2, neither age at implantation nor age at testing predicted disyllable or sentence recognition. Performance was significantly better with the female than with the male talkers.

Conclusions

Consistent with previous studies’ findings, early implantation provided a significant advantage for profoundly deaf children. Performance for both groups was generally quite good for the relatively difficult materials and tasks, suggesting that open-set word and sentence recognition may be useful in evaluating speech performance with older pediatric CI users. Differences in disyllable recognition between Groups 1 and 2 may reflect differences in adaptation to electric stimulation. The Group 1 subjects developed speech patterns exclusively via electric stimulation, while the Group 2 subjects adapted to electric stimulation relative to previous acoustic patterns.     

Fitting prelingually deafened adult cochlear implant users based on electrode discrimination performance

Objective: This study investigated the hypotheses that (1) prelingually deafened CI users do not have perfect electrode discrimination ability and (2) the deactivation of non-discriminable electrodes can improve auditory performance. Design: Electrode discrimination difference limens were determined for all electrodes of the array. The subjects’ basic map was subsequently compared to an experimental map, which contained only discriminable electrodes, with respect to speech understanding in quiet and in noise, listening effort, spectral ripple discrimination and subjective appreciation. Study Sample: Subjects were six prelingually deafened, late implanted adults using the Nucleus cochlear implant. Results: Electrode discrimination difference limens across all subjects and electrodes ranged from 0.5 to 7.125, with significantly larger limens for basal electrodes. No significant differences were found between the basic map and the experimental map on auditory tests. Subjective appreciation was found to be significantly poorer for the experimental map. Conclusions: Prelingually deafened CI users were unable to discriminate between all adjacent electrodes. There was no difference in auditory performance between the basic and experimental map. Potential factors contributing to the absence of improvement with the experimental map include the reduced number of maxima, incomplete adaptation to the new frequency allocation, and the mainly basal location of deactivated electrodes.     

Perception of speech by prelingual pre-adolescent and adolescent cochlear implant users

Abstract

This study was undertaken to assess the speech perception benefits, 24 months after cochlear implantation (CI), in 20 young people (age at CI, 8–18.5 years) with prelingual profound hearing loss, in addition to the use of a proposed CI candidacy assessment profile. Speech perception was evaluated in terms of word and sentence perception before CI, and at six-monthly intervals for two years after CI. Before undergoing CI, all participants were tested on a pre-implantation assessment profile. Compared to the pre-CI findings, group results over 24 months post-CI demonstrated improved speech perception abilities reaching, on average, 46% for word recognition, 71.3% for sentences in quiet, and 33.6% for sentences in noise. Pre-CI profile scores correlated significantly with all speech perception results obtained 24 months after CI. Thus, despite their relatively late ages at implantation, all participants showed gradually improving performance in speech perception. The results showed a high variability in the outcomes of the participants. The pre-CI profile appeared to be useful in formulating realistic expectations of CI outcome during pre-implantation consultations, suggesting that expectations can and should be managed according to each patient's pre-implantation assessment.

Sumario

Se llevó a cabo este estudio para evaluar los beneficios en la percepción del lenguaje, 24 meses después de la implant-ación coclear (CI), en 20 personas jóvenes (edad en la CI de 8-18.5 años), con sordera prelingüística profunda, en quienes se usó un perfil propuesto de evaluación para la candidatura a la CI. La percepción del lenguaje se evaluó en términos de percepción de palabras y oraciones antes de la CI y a intervalos de seis meses, durante dos años, después de la CI. Antes de la CI todos los participantes fueron examinados con un perfil de evaluación pre-implantación. Comparados con los hallazgos pre-CI, los resultados del grupo después de 24 meses de la CI mostraron mejoría en las habilidades para la percepción del lenguaje alcanzando, en promedio, 46% para el reconocimiento de palabras, 71.3% para oraciones sin ruido y 33.6% para oraciones con ruido. Las puntuaciones en el perfil pre-CI correlacionaron significativamente con todos los resultados de percepción del lenguaje obtenidos 24 meses después de la CI. Así, a pesar de las edades de implantación relativamente tardías, todos los participantes mostraron un desempeño gradual-mente mejor en la percepción del lenguaje. Los resultados mostraron una gran variabilidad en los resultados de los participantes. El Perfil pre-CI parece ser útil para formular expectativas realistas sobre los resultados de la CI durante las consultas pre-implante, sugiriendo que las expectativas pueden y deben ser manejadas de acuerdo con las evaluaciones pre-implantación de cada paciente.     

Voice gender discrimination provides a measure of more than pitch-related perception in cochlear implant users

Abstract

Objectives: (1) To investigate whether voice gender discrimination (VGD) could be a useful indicator of the spectral and temporal processing abilities of individual cochlear implant (CI) users; (2) To examine the relationship between VGD and speech recognition with CI when comparable acoustic cues are used for both perception processes. Design: VGD was measured using two talker sets with different inter-gender fundamental frequencies (F₀), as well as different acoustic CI simulations. Vowel and consonant recognition in quiet and noise were also measured and compared with VGD performance. Study sample: Eleven postlingually deaf CI users. Results: The results showed that (1) mean VGD performance differed for different stimulus sets, (2) VGD and speech recognition performance varied among individual CI users, and (3) individual VGD performance was significantly correlated with speech recognition performance under certain conditions. Conclusions: VGD measured with selected stimulus sets might be useful for assessing not only pitch-related perception, but also spectral and temporal processing by individual CI users. In addition to improvements in spectral resolution and modulation detection, the improvement in higher modulation frequency discrimination might be particularly important for CI users in noisy environments.

Sumario

Objetivos: (1) Investigar si la discriminación de voz por género (VGD) puede ser un indicador útil de las habilidades de procesamiento espectral y temporal de usuarios de implantes cocleares (IC); (2) Examinar la relación entre VGD y el reconocimiento del lenguaje con IC, cuando se usan claves acústicas comparables para ambos procesos de percepción. Diseño: Se midió el VGD usando dos series de hablantes con diferentes frecuencias fundamentales (Fo) inter-género así como diferentes simulaciones acústicas de IC. El reconocimiento de vocales y consonantes en silencio y con ruido también se midió y comparó con el rendimiento VGD. Muestra: Once usuarios sordos de IC post-lingüísticos. Resultados: Los resultados mostraron que 1) el rendimiento promedio VGD difirió para diferentes grupos de estímulos; 2) el rendimiento para el reconocimiento de VGD y de lenguaje varió entre usuarios de IC y 3) el rendimiento individual de VGD correlacionó significativamente con el reconocimiento del lenguaje bajo ciertas condiciones. Conclusiones: El VGD medido con grupos seleccionados de estímulos puede ser útil para evaluar no solamente la percepción relacionada con la frecuencia sino también el procesamiento espectral y temporal en usuarios de IC. Además de la mejoría en la resolución espectral y en la detección de la modulación, la mejoría en la discriminación en frecuencias de alta modulación puede ser particularmente importante para los usuarios de IC en ambientes de ruido.     

Effects of residual speech and auditory deprivation on speech perception of adult cochlear implant recipients

Objective

Possible predictive factors of cochlear implant (CI) outcomes have been extensively reported in literature for different user groups such as prelingual pediatric or postlingual adult users. However, there remains unexplained outcome variability among adult CI users; therefore, research concerning these patients continues and many different variables have been reported. This study aimed at evaluating the relationship between preoperative speech reception capacity, residual hearing, duration of deafness, age of implantation, and postoperative monosyllabic word recognition scores (WRSs) in postlingual CI users.

Computer-based auditory phoneme discrimination training improves speech recognition in noise in experienced adult cochlear implant listeners

Objective: Specific computer-based auditory training may be a useful completion in the rehabilitation process for cochlear implant (CI) listeners to achieve sufficient speech intelligibility. This study evaluated the effectiveness of a computerized, phoneme-discrimination training programme. Design: The study employed a pretest-post-test design; participants were randomly assigned to the training or control group. Over a period of three weeks, the training group was instructed to train in phoneme discrimination via computer, twice a week. Sentence recognition in different noise conditions (moderate to difficult) was tested pre- and post-training, and six months after the training was completed. The control group was tested and retested within one month. Study sample: Twenty-seven adult CI listeners who had been using cochlear implants for more than two years participated in the programme; 15 adults in the training group, 12 adults in the control group. Results: Besides significant improvements for the trained phoneme-identification task, a generalized training effect was noted via significantly improved sentence recognition in moderate noise. No significant changes were noted in the difficult noise conditions. Improved performance was maintained over an extended period. Conclusions: Phoneme-discrimination training improves experienced CI listeners’ speech perception in noise. Additional research is needed to optimize auditory training for individual benefit.     

人工耳蜗植入电极分布频带不同排列模式对语言识别能力的影响

目的通过测试电子耳蜗植入患者电极分布频带颠倒排列前后声音识别的变化,探讨电极分布频带排列模式对声音识别能力的影响。方法15名电子耳蜗植入患者,分别依次测试电极分布频带颠倒排列前后对铃声（代表高频）和鼓声（代表低频）两种不同声音的识别能力,记录并分析结果。结果在电极分布频带按低频对应蜗尖、高频对应蜗底的正常顺序排列时,均能准确识别出铃声和鼓声。在电极分布频带颠倒排列后,13名受试者将铃声和鼓声均识别为鼓声,另2名则将铃声识别为鼓声,而将鼓声识别为铃声。结论电子耳蜗电极分布频带排列模式改变可以影响电子耳蜗植入患者对声音的识别能力。     

The long-term results of speech perception in elderly cochlear implant users

Objectives: To evaluate the speech discrimination performance of elderly post-lingually deafened cochlear implant (CI) users and the stability of performance over time relative to a control group of younger CI users.

Methods: The study group consisted of 20 native Dutch speaking, post-lingually deafened CI users, aged 70 or older at the time of implantation. Controls were patients aged 40–60 years at implantation and included according to the same inclusion criteria (except age). Linear mixed models assessed speech recognition scores between groups, the variability of their performance, and stability over time.

Results: 20 elderly and 37 controls were included. The mean follow-up was 4.4 and 5.3 years for elderly and controls, respectively. There was no significant difference in average speech discrimination between both groups. The elderly group had a larger intra-subject variability over time. There was no significant effect of follow-up on the speech discrimination, indicating a stable performance over time.

Discussion: This study has a longer follow-up than methodologically comparable previous studies. We found no difference in speech discrimination between elderly patients and controls and no deterioration of performance over time. The subjects in the elderly group exhibit a larger variability around their mean performance.

Conclusion: Speech recognition in both elderly and younger adult CI users is stable over time and is not significantly related to the age of implantation.     

Effects of electrode deactivation on speech recognition in multichannel cochlear implant recipients

Objectives: The objective of the current study is to evaluate how speech recognition performance is affected by the number of active electrodes that are turned off in multichannel cochlear implants. Several recent studies have demonstrated positive effects of deactivating stimulation sites based on an objective measure in cochlear implant processing strategies. Previous studies using an analysis of variance have shown that, on average, cochlear implant listeners’ performance does not improve beyond eight active electrodes. We hypothesized that using a generalized linear mixed model would allow for better examination of this question.

Methods: Seven peri- and post-lingual adult cochlear implant users (eight ears) were tested on speech recognition tasks using experimental MAPs which contained either 8, 12, 16 or 20 active electrodes. Speech recognition tests included CUNY sentences in speech-shaped noise, TIMIT sentences in quiet as well as vowel (CVC) and consonant (CV) stimuli presented in quiet and in signal-to-noise ratios of 0 and +10?dB.

Results: The speech recognition threshold in noise (dB SNR) significantly worsened by approximately 2?dB on average as the number of active electrodes was decreased from 20 to 8. Likewise, sentence recognition scores in quiet significantly decreased by an average of approximately 12%.

Discussion/conclusion: Cochlear implant recipients can utilize and benefit from using more than eight spectral channels when listening to complex sentences or sentences in background noise. The results of the current study suggest a conservative approach for turning off stimulation sites is best when using site-selection procedures.     

Outcome evaluation on cochlear implant users with residual hearing

Objectives: The performance outcome with Freedom? Hybrid? versus the CP900 series sound processor with Hybrid Hearing was investigated. In addition, a preliminary evaluation was conducted to consider the feasibility of upgrading experienced electric-only cochlear implant (CI) users who had substantial residual hearing to Hybrid Hearing.

Methods: This study was a single-centre prospective, non-inferiority design with repeated measures conducted at Hannover Medical School (MHH). The randomized AABB cross-over design to compensate for learning effects included two test groups. Group 1 compared two systems for Hybrid Hearing (Freedom Hybrid sound processor versus CP900 series sound processor) and Group 2 compared CP900 series sound processor (electric-only) versus the CP900 with Hybrid Hearing in experienced CI users who had confirmed residual low-frequency hearing. Groups 1 and 2 were composed of different participants.

Results: Group 1 (n?=?24) performance on speech perception tests was equivalent or superior with the CP900 series sound processor showing a statistically significant mean improvement of 1.87?dB in background noise (P?P?=?0.064) for participants tested with the CP900. The patient-reported outcome questionnaire confirmed the beneficial performance with the CP900 series sound processor with Hybrid Hearing. The feasibility portion of the study (Group 2, n?=?14) showed an average benefit of 0.54?dB in background noise when using the CP900 with Hybrid Hearing function versus electric-only stimulation.

Conclusions: The outcome presents sufficient evidence to show the effectiveness of the CP900 series sound processor with Hybrid Hearing over the Freedom Hybrid for participants with substantial residual hearing. Positive outcomes were observed for improved speech understanding and subjective hearing performance. Further, a trend was demonstrated in the data towards better performance with CP900 with Hybrid Hearing versus electric-only stimulation. Hybrid Hearing users showed a clinically relevant and statistically a significant benefit from the current CP900 series sound processor generation supporting its recommendation, on a case-by-case basis, to current electric-only users. More research is needed to confirm these findings.     

Correlative studies of cochlear neuronal loss with speech discrimination and pure-tone thresholds

Summary Correlations were made between speech discrimination scores, pure-tone thresholds, and neuronal populations in 28 cochleae which were removed postmortem from elderly patients who had known premortem audiometric records. The predominant pathology present was loss of cochlear neurons. The capability for speech discrimination correlated directly with the innervation density of the 15- to 22-mm region (segment III) of the cochlea. Speech discrimination scores showed an inverse relationship to pure-tone thresholds in the middle frequency range of 1 kHz to 2 kHz.Supported by the National Institute of Neurlogical and Communicative Disorders and Stroke, grant no. 5 ROI NS05881     

语前聋儿童人工耳蜗植入效果的评估

目的探索语前聋儿童人工耳蜗植入效果的评估方法.方法受试者为18名接受人工耳蜗植入的语前聋儿童,耳蜗植入时平均年龄6岁.按人工耳蜗使用时间长短分为四个阶段进行评估:第一阶段18名患儿,使用人工耳蜗1～12个月;第二阶段12名,使用人工耳蜗13～24个月;第三阶段8名,使用人工耳蜗25～36个月;第四阶段6名,使用人工耳蜗在36个月以上.描述性分析,以问卷的形式了解儿童在人工耳蜗植入后声音接受、言语表达及行为等方面的变化;言语测试,进行言语识别能力和发声能力测试.结果第一阶段患儿,能够感知和辨别来自家庭和环境中的声音;第二阶段患儿,封闭项词识别率是51%,开放项词识别开始启动;第三阶段患儿,封闭项词识别率达到72%,开放项词识别率是40%,能正确发出的单词数是42%;第四阶段患儿,封闭项词识别率和开放项词识别率分别达到84%和53%,能正确发出的单词数达62%,部分患儿已有自发的口语表达.结论人工耳蜗植入对语前聋患儿的言语发育有帮助,患儿的言语能力随着人工耳蜗使用时间的推移不断进步.     

Prior exposure to a reverberant listening environment improves speech intelligibility in adult cochlear implant listeners

Objectives: The goal of this study is to investigate whether prior exposure to reverberant listening environment improves speech intelligibility of adult cochlear implant (CI) users.

Methods: Six adult CI users participated in this study. Speech intelligibility was measured in five different simulated reverberant listening environments with two different speech corpuses. Within each listening environment, prior exposure was varied by either having the same environment across all trials (blocked presentation) or having different environment from trial to trial (unblocked).

Results: Speech intelligibility decreased as reverberation time increased. Although substantial individual variability was observed, all CI listeners showed an increase in the blocked presentation condition as compared to the unblocked presentation condition for both speech corpuses.

Conclusion: Prior listening exposure to a reverberant listening environment improves speech intelligibility in adult CI listeners. Further research is required to understand the underlying mechanism of adaptation to listening environment.     

Optimizing the perception of soft speech and speech in noise with the Advanced Bionics cochlear implant system

Abstract

Objective: This study aimed to provide guidelines to optimize perception of soft speech and speech in noise for Advanced Bionics cochlear implant (CI) users. Design: Three programs differing in T-levels were created for ten subjects. Using the T-level setting that provided the lowest FM-tone, sound-field threshold levels for each subject, three additional programs were created with input dynamic range (IDR) settings of 50, 65 and 80 dB. Study sample: Subjects were postlinguistically deaf adults implanted with either the Clarion CII or 90K CI devices. Results: Sound-field threshold levels were lowest with T-levels set higher than 10% of M-levels and with the two widest IDRs. Group data revealed significantly higher scores for CNC words presented at a soft level with an IDR of 80 dB and 65 dB compared to 50 dB. Although no significant group differences were seen between the three IDRs for sentences in noise, significant individual differences were present. Conclusions: Setting Ts higher than the manufacturer's recommendation of 10% of M-levels and providing IDR options can improve overall speech perception; however, for some users, higher Ts and wider IDRs may not be appropriate. Based on the results of the study, clinical programming recommendations are provided.

Sumario

Objetivo: Este estudio buscó proporcionar pautas para optimizar la percepción del lenguaje suave y del lenguaje en ruido para usuarios del implante coclear (IC) de Advanced Bionics. Diseño: Se crearon tres programas para diez pacientes, que eran diferentes en sus niveles T. Al usar el control de nivel T que proporcionaba el tono FM más bajo, con niveles de umbral en campo libre para cada sujeto, se crearon tres programas adicionales con controles de ingreso del rango dinámico IRD de 50, 65 y 80 dB. Muestra de Estudio: Los sujetos fueron sordos adultos postlingüísticos implantados con los modelos Clarion CII o 90K CI. Resultados: Los niveles de umbral en campo libre fueron más bajos con los niveles T colocados 10% más alto que los niveles M y con los dos IDR más anchos. Los datos del grupo revelaron puntuaciones significativamente mayores con palabras CNC presentadas en un nivel suave con un IDR de 80 dB y 65 dB comparados con 50 dB. No obstante que no se encontraron diferencias significativas en los grupos entre los tres IDR para oraciones en ruido, si se presentaron diferencias significativas individuales. Conclusiones: La colocación de los niveles T más altos en 10% que la recomendación del fabricante, sobre los niveles M y el proporcionar opciones de IDR, en general pueden mejorar la percepción del lenguaje; no obstante, niveles mayores de T y IDR más anchas, pueden no ser apropiados para algunos usuarios. Con base en los resultados de este estudio, se proporcionan recomendaciones clínicas para la programación.     

低年龄段语前聋儿童人工耳蜗植入后汉语声调识别变化的分析

目的:探讨低年龄段经人工耳蜗植入的语前聋儿童经过开机一段时间后声调识别的变化特点。方法:选择29例已经接受人工耳蜗植入的低年龄语前聋儿童,按植入时年龄分为2组,即A组:3.0~4.5岁,B组:5.0~6.5岁,植入后平均开机时间为1.5~2.0年。采用聋康系统的《聋儿听觉言语康复评估词表》中主要反映声调识别的相应评估内容进行封闭项测试。结果:A组:同音单音节声调识别率为(63.00±16.75)%,双音节声调识别率为(75.60±11.18)%,单音节词识别率为(72.38±11.39)%。B组:同音单音节声调识别率为(49.46±13.91)%,双音节声调识别为(64.71±9.64)%,单音节词识别率为(55.71±8.59)%。所有正确识别率结果均大于机会水平。人工耳蜗植入后不同年龄组患儿有关声调识别的三项测试内容,低年龄组患儿均好于高年龄组,结果均差异有统计学意义。结论:对于语前聋行人工耳蜗植入的低年龄儿童,植入时年龄仍是影响植入后声调识别的重要因素之一,而在更能反映汉语声、韵、调特点的单音节词中差异更为明显,因此植入年龄是术后汉语学习的重要影响因素之一。     

Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors

Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with Nucleus™ systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode, the lower and upper limits of electric stimulus were defined by the values corresponding to “very soft” and “too loud”. Within this dynamic range, the stimulus strength intervals associated to the verbal categories “soft”, “medium”, “loud” and “very loud” were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments, the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue in favour of the development of flexible and channel-specific mapping function parameters in future CI systems. Parts of this paper were presented at the 76th annual meeting of the Deutsche Gesellschaft für HNO-Heilkunde, Kopf- und Hals-Chirurgie in Erfurt on 8 May 2005.     

Influence of stimulation rate and loudness growth on modulation detection and intensity discrimination in cochlear implant users

In cochlear implants (CIs), increasing the stimulation rate typically increases the electric dynamic range (DR), mostly by reducing audibility thresholds. While CI users’ intensity resolution has been shown to be fairly constant across stimulation rates, high rates have been shown to weaken modulation sensitivity, especially at low listening levels. In this study, modulation detection thresholds (MDTs) were measured in five CI users for a range of stimulation rates (250–2000 pulses per second) and modulation frequencies (5–100 Hz) at 8 stimulation levels that spanned the DR (loudness-balanced across stimulation rates). Intensity difference limens (IDLs) were measured for the same stimulation rates and levels used for modulation detection. For all modulation frequencies, modulation sensitivity was generally poorer at low levels and at higher stimulation rates. CI users were sensitive to modulation frequency only at relatively high levels. Similarly, IDLs were poorer at low levels and at high stimulation rates. When compared directly in terms of relative amplitude, IDLs were generally better than MDTs at low levels. Differences in loudness growth between dynamic and steady stimuli might explain level-dependent differences between MDTs and IDLs. The slower loudness growth associated with high stimulation rates might explain the poorer MDTs and IDLs with high rates. In general, high stimulation rates provided no advantage in intensity resolution and a disadvantage in modulation sensitivity.     

语速和耳语对人工耳蜗植入者言语识别效果的影响

目的研究不同语速和耳语式的言语是否会影响人工耳蜗植入者的言语识别效果。方法在本研究中,分别对一组人工耳蜗植入者和一组听力正常者进行以下4种不同说话方式的言语识别率测试：慢速言语、常速言语、快速言语和耳语。测试时,人工耳蜗植入者聆听由扬声器播放的未经处理的言语声,正常受试者聆听经4通道人工耳蜗处理的言语声,二者使用相同的原始测试材料。结果人工耳蜗植入组与正常对照组对4种不同说话方式的言语识别结果相似,当说话语速增加时言语识别率逐渐下降,耳语的识别率最差,对于人工耳蜗植入者来说快速言语的识别率显著低于慢速言语识别率。结论人工耳蜗植入者言语识别效果会随着所聆听言语的语速增加而降低,并且聆听耳语式的言语对人工耳蜗植入者来说是非常困难的。