• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.249-255
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• 2012

A cochlear implant system uses charge-balanced biphasic pulses that are known to reduce tissue damage than monophasic pulses. In this study, we investigated effect of pulse pattern on neural responses using a computer model, based on the Hodgkin-Huxley equation. Electric pulse phase, pulse duration, and phase gap have been systematically varied to characterize auditory nerve responses. The results show that neural responses, dynamic range and threshold are represented as a function of stimulus patterns and duration. The results could greatly extend to develop more efficient cochlear implant stimulation.

• Phonetics and Speech Sciences
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• v.5 no.4
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• pp.71-78
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• 2013

The purpose of this study was to compare the acoustic voice outcomes of children with cochlear implant to those of children with normal hearing. Participants were 41 children using unilateral cochlear implant (18 males and 23 females), and children with normal hearing from the same age and sex. Mean age of implantation was approximately 3 years old, mean duration of implant use was 4 years in CI group. Acoustic analyses were performed using MDVP of CSL. Speech samples were 3 sustained vowels, /a, i, u/. 9 parameters (F0, Fhi, Flo, Jitter, Shimmer, vF0, vAm, NHR, and SPI) were analyzed. Children with CI did not show the significant differences in those parameters after the vowel /a/ phonation. Meanwhile, there were significantly different results in F0, Fhi, vF0, and SPI after /i, u/ phonation. These results revealed that differences of voice characteristics in children with CI compare to children with NH persist regarding vowel context. It suggests that high vowels would recommend as speech samples for acoustic evaluation. Futhermore perceptual analysis and speech therapy for phonation control would be necessary for children with CI.

• Speech Sciences
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• v.10 no.4
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• pp.181-187
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• 2003

This paper introduces a new zinc coated copper wire electrode with coiled cone shape which has low surface resistance and tolerance to the motion artifact for promontory stimulation electrically auditory brainstem responses (PSEABR). Auditory brainstem responses (ABR) can be used to predict hearing threshold level with a great deal of accuracy particularly for a young child who cannot cooperate mechanically and some hearing impaired who are exaggerating a hearing loss for economic compensation. While severe profound sensorineural hearing losses may not be implemented by auditory potentials, PSEABR is proven as a useful tool even for some sensorineural related hearing impaired. It was shown that PSEABR gives the electrical stimuli to promontory of the cochlear instead of giving acoustic stimuli. For this reason, PSEABR can be used as an alternative for cochlear implantation, and can also be used as an optimal device selection and neural information for MAP. It was found that the role of electrode is very important in PSEABR. Even though this cone-shaped electrode was applied in animal experiments, waveforms are well produced by PSEABR. Thus, it was concluded that cone-shaped electrode turned out to be a useful preoperative audiological evaluation tool in deciding time for cochlear implantation surgery.

• Speech Sciences
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• v.14 no.2
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• pp.35-42
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• 2007

The aim of this study is to analyze the correlation between current intensity and amplitude of stimulus artifact on the cochlear implantee, and to find out basic information to check the device failure. Subjects were a prelingual child and 3 postlingual adults with more than severe hearing losses. The charge-balanced biphasic pulses were presented at stimulus rates of 11 pulses per second, each pulse width of $25{\mu}s$ with monopolar mode(MP1+2). Current intensities were delivered at 27.5, 33.7, 41.3, 50.5, 61.9, $75.8{\mu}A$. Stimulus artifacts were recorded by evoked potential system. This procedure was performed just before the initial stimulation, and then, the amplitude of stimulus artifacts were compared with each current intensity. The amplitude of stimulus artifacts was increased significantly according to the current intensity (p<0.01). The results suggest that the change of the amplitude of stimulus artifact can be used as a good cue to check the device failure in the cochlear implantee.

• Phonetics and Speech Sciences
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• v.3 no.1
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• pp.117-123
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• 2011

Most individuals with hearing impairment have difficulty in understanding speech in noisy situations. This study was conducted to investigate sentence recognition ability using the Korean Standard-Sentence Lists for Preschoolers (KS-SL-P2) in pre-school age children with cochlear implants and hearing aids. The subjects of this study were 10 pre-school age children with hearing aids, 12 pre-school age children with cochlear implants, and 10 pre-school age children with normal hearing. Three kinds of signal-to-noise (SNR) conditions (+10 dB, +5 dB, 0 dB) were applied. The results for all pre-school age children with cochlear implants and hearing aids presented a significant increase in the score for sentence recognition as SNR increased. The sentence recognition score in speech noise were obtained with the SNR +10 dB. Significant differences existed between groups in terms of their sentence recognition ability, with the cochlear implant group performing better than the hearing aid group. These findings suggest the presence of a sentence recognition test using speech noise is useful for evaluating pre-school age children's listening skill.

• Journal of Preventive Medicine and Public Health
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• v.37 no.4
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• pp.353-358
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• 2004

Objective : To determine the quality of life and cost consequences for deaf adults who received a cochlear implant. Methods : The data from 11 patients, post-lingual deaf adults who received cochlear implants from 1990 to 2002, underwent cost-utility analysis. The average age of the participants was 49.6 years. The main outcomes were direct cost per quality-adjusted life-year (QALY) using the visual analog scale (VAS), health utility index (HUI), EuroQol (EQ-5D), and quality well-being (QWB), with costs and utilities being discounted 3% annually. Results : Recipients had an average of 5.6 years of implant use. Mean VAS scores increased by 0.33, from 0.27 before implantation to 0.60 at survey. HUI scores increased by 0.36, from 0.29 to 0.65, EQ-5D scores increased by 0.26, from 0.52 to 0.78, and QWB scores increased by 0.16, from 0.45 to 0.61. Discounted direct costs were $22,320, yielding $19,223/QALY using VAS, $17,387/QALY using HUI, $24,604/QALY using EQ-5D, and $40,474/QALY using QWB. Cost-utility ratios using VAS, HUI, and EQ-5D were all below $25,000 per QALY, except using QWB. Conclusion : Cochlear implants in post-lingual deaf adult have a positive effect on quality of life at reasonable direct costs and appear to produce a net saving to society.

• Journal of Sensor Science and Technology
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• v.22 no.2
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• pp.150-155
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• 2013

Recently, various hearing aids are developed to overcome hearing loss. There are available hearing aids, such as air conduction hearing aid, implantable middle ear hearing aid and so on. But air conduction hearing aid is inconvenience caused by howling, and ossicle chain driving type implantable middle ear hearing aid has some week point due to problem of possible nercobiosis of coupling spot along incus long process. In recent years, in order to improve these shortcomings round window (RW) driving hearing aid has been paying attention. In this paper, the physical cochlear model is proposed for a performance evaluation of the RW driving hearing aids of a transducer. In order to verify an experiment proposed on a performance of physical cochlear model, the transducer which has ossicles characteristics is used. By measuring and comparing the frequency characteristics of transducer with ossicles and human temporal bone, performance of physical cochlear model was verified. As from the result of experiment, it is expected that an implemented cochlear model is useful for evaluating characteristics of RW transducer.

• MALSORI
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• no.62
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• pp.33-49
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• 2007

The purpose of this study is 1) to investigate the phoneme inventories and phonological processes of cochlear implant(CI) children and 2) to describe their utterances using narrow phonetic transcription method. All ten subjects had more than 2 year-experience with CI and showed more than 85 % open-set sentence perception abilities. Average consonant accuracy was 81.36 % and it was improved up to 87.41% when distortion errors were not counted. They showed similar phonological processing patterns to HA or normal hearing children in some way as well as different phonological processing patterns from HA or normal hearing children. The prominent distortion error pattern was weakening of consonants. Every subject had his/her idiosyncratic error pattern that demanded his/her own individualized therapy program.

• Electronics and Telecommunications Trends
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• v.8 no.2
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• pp.69-91
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• 1993

In the conventional speech processing, the technique of FFT(Fast Fourier Transform) is usually applied to the finite number of samples within the window of specified length using the fixed sampling rate. In this case, the temporal resolution is dependent upon the length of window while the spectral resolution is dependent upon the number of samples within the window. Thus, once the temporal resolution is determined the spectral resolution is also determined or vice versa. To resolve this type of dilemma, a new type of bank-filter similar to the characteristics of cochlear model needs to be considered. Furthermore, wide dynamic range of cochlea certainly helps the stable extraction of speech features. In the paper, the human auditory system will be briefly introduced and previous works on auditory preprocessors based on cochlear model will be reviewed. As a conclusion, the design considerations of auditory preprocessors based on cochlear model will be addressed.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.205-211
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• 2007

A novel envelope extraction algorithm for speech processor of cochlear implants, called adaptation algorithm, was developed which is based on a adaptation effect of the inner hair cell(IHC)/auditory nerve(AN) synapse. We achieved acoustic simulation and hearing experiments with 12 normal hearing persons to compare this adaptation algorithm with existent standard envelope extraction method. The results shows that speech processing strategy using adaptation algorithm showed significant improvements in speech recognition rate under most channel/noise condition, compared to conventional strategy We verified that the proposed adaptation algorithm may yield better speech perception under considerable amount of noise, compared to the conventional speech processing strategy.