Compression and Cochlear Implants

Zeng, Fan-Gand

doi:10.1007/0-387-21530-1_6

Cited by 19 publications

(14 citation statements)

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“…In Experiment 2, the temporal envelope cue in the High model was not sufficient to segregate speech streams. This result may not be valid in actual cochlear implant users because the cochlear implant users can detect modulations better than normally hearing individuals (Shannon, 1993;Kohlrausch et al, 2000;Zeng, 2004). The number of spectral channels in Experiment 3 greatly exceeded the number of usable spectral channels in actual cochlear implants.…”

Section: Implications For Cochlear Implantsmentioning

confidence: 47%

“…The sub-band envelope was then used to modulate a pure tone at the center of each frequency band (Shannon et al, 1995;Dorman et al, 1997). A pure tone carrier, rather than a noise carrier, was used to simulate the cochlear implant users' better than normal performance in temporal modulation detection (Shannon, 1993;Kohlrausch et al, 2000;Zeng, 2004). Finally, the output of the modulated sub-band signal was passed through the original analysis filter to remove any sidebands induced by the modulation that exceed the channel width.…”

Section: Subjectsmentioning

confidence: 99%

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Fundamental frequency discrimination and speech perception in noise in cochlear implant simulations

Carroll

Zeng

2007

Hearing Research

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Increasing the number of channels at low frequencies improves discrimination of fundamental frequency (F0) in cochlear implants (Geurts, L., Wouters, J., 2004. Better place-coding of the fundamental frequency in cochlear implants. J. Acoust. Soc. Am. 115 (2), 844-852). We conducted three experiments to test whether improved F0 discrimination can be translated into increased speech intelligibility in noise in a cochlear implant simulation. The first experiment measured F0 discrimination and speech intelligibility in quiet as a function of channel density over different frequency regions. The results from this experiment showed a tradeoff in performance between F0 discrimination and speech intelligibility with a limited number of channels. The second experiment tested whether improved F0 discrimination and optimizing this tradeoff could improve speech performance with a competing talker. However, improved F0 discrimination did not improve speech intelligibility in noise. The third experiment identified the critical number of channels needed at low frequencies to improve speech intelligibility in noise. The result showed that, while 16 channels below 500Hz were needed to observe any improvement in speech intelligibility in noise, even 32 channels did not achieve normal performance. Theoretically, these results suggest that without accurate spectral coding, F0 discrimination and speech perception in noise are two independent processes. Practically, the present results illustrate the need to increase the number of independent channels in cochlear implants.

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Section: Implications For Cochlear Implantsmentioning

confidence: 47%

Section: Subjectsmentioning

confidence: 99%

Fundamental frequency discrimination and speech perception in noise in cochlear implant simulations

Carroll

Zeng

2007

Hearing Research

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“…The rationale for the linear scale is based on the physiological observation that the linear current is directly related to the response of the nerve population, which is attributed to the lack of peripheral compression in electric hearing (Zeng 2004). For this reason, the linear current scale might be preferable when comparing two currents within the same stimulation setting (i.e., in one subject or in the same electrode configuration).…”

Section: Procedures and Notation Of Resultsmentioning

confidence: 99%

Spatial and Temporal Effects of Interleaved Masking in Cochlear Implants

Kwon

Honert

2009

JARO

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Modern cochlear implants utilize interleaved presentation of pulses on different electrodes to avoid physical interference among multiple current fields, yet neural interaction still exists. In the present study, masking was examined with four Nucleus24 users with the banded electrode array in an interleaved masking paradigm, where a probe stimulus was interleaved with a masker stimulus. Spatial and temporal aspects of masking were addressed by fixing the masker at the middle of the electrode array and changing the location of the probe and by testing various stimulation rates: 125, 500, 2,000, and 6,410 Hz. In addition, growth of masking (GOM) was assessed by changing the masker level in six steps. Results indicated that masking patterns were generally much wider, regardless of stimulation rate, than those in acoustic hearing. The amount of masking decreased from the peak at the rate of approximately 0.5 dB/mm even at the highest masker level. The pattern of GOM with the rates higher than 500 Hz was different from that observed in previous masking studies, characterized by markedly shallow growth at low masker levels or overall shallow growth. A facilitating effect of the masker (lowering the threshold) was suspected, except for the 125-Hz condition, due to the fibers that were subliminally excited, but not discharged, by the masker with local perturbations of membrane potentials, and were subsequently discharged easily by a lower level probe when the temporal gap between masker and probe was sufficiently short. These results suggest that both refractory characteristics of neurons and neural summation be considered in interleaved stimulation of pulses at high, but clinically relevant, stimulation rates. Overall, the present masking study might provide a basis for models in psychophysics and speech understanding in current cochlear implant systems utilizing high-rate interleaved stimulation.

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“…Different from a power function in normal loudness growth and a wide 100-120 dB dynamic range, cochlear implant users typically have an exponential loudness growth function and a much narrower 10-20 dB dynamic range. The altered loudness growth and the reduced dynamic range are to large extent due to the damaged cochlea [190] and can be compensated effectively by the amplitude compression circuitry in the speech processor. The temporal pitch is limited to 300-500 Hz in a typical cochlear implant user, whereas pitch above this frequency may be provided by place pitch, as evidenced by the different saturation points between apical and basal electrodes at 1000-2000 Hz high stimulation rates.…”

Section: System Evaluationmentioning

confidence: 99%

Cochlear Implants: System Design, Integration, and Evaluation

Zeng

Rebscher

Harrison³

et al. 2008

IEEE Rev. Biomed. Eng.

674

198

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As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120,000 persons worldwide; half of which being pediatric users who are able to develop nearly normal language. Biomedical engineers have played a central role in the design, integration and evaluation of the cochlear implant system, but the overall success is a result of collaborative work with physiologists, psychologists, physicians, educators, and entrepreneurs. This review presents broad yet in-depth academic and industrial perspectives on the underlying research and ongoing development of cochlear implants. The introduction accounts for major events and advances in cochlear implants, including dynamic interplays among engineers, scientists, physicians, and policy makers. The review takes a system approach to address critical issues from design and specifications to integration and evaluation. First, the cochlear implant system design and specifications are laid out. Second, the design goals, principles, and methods of the subsystem components are identified from the external speech processor and radio frequency transmission link to the internal receiver, stimulator and electrode arrays. Third, system integration and functional evaluation are presented with respect to safety, reliability, and challenges facing the present and future cochlear implant designers and users. Finally, issues beyond cochlear implants are discussed to address treatment options for the entire spectrum of hearing impairment as well as to use the cochlear implant as a model to design and evaluate other similar neural prostheses such as vestibular and retinal implants.

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Compression and Cochlear Implants

Cited by 19 publications

References 100 publications

Fundamental frequency discrimination and speech perception in noise in cochlear implant simulations

Fundamental frequency discrimination and speech perception in noise in cochlear implant simulations

Spatial and Temporal Effects of Interleaved Masking in Cochlear Implants

Cochlear Implants: System Design, Integration, and Evaluation

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