The Effect of Front-End Processing on Cochlear Implant Performance of Children

Wolfe, Jace; Schafer, Erin C.; John, Andrew; Hudson, Mary

doi:10.1097/mao.0b013e318210b6ec

Cited by 33 publications

(32 citation statements)

References 18 publications

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“…ASC aims to adaptively adjust the sensitivity control to prevent infinite compression of high-level speech signals in noisy environments (i.e., sensitivity decreases when ambient noise >57 dB SPL) and therefore significantly improves speech recognition in noise and comfort for adults and children with cochlear implants relative to a fixed sensitivity setting ( Wolfe et al , 2011Gifford & Revit 2010). The sensitivity control shifts theIIDR window up or down depending upon the setting of the control.…”

Section: Effect Of Cochlear Implant Input Processing On Performance Wmentioning

confidence: 99%

Effects of Input Processing and Type of Personal Frequency Modulation System on Speech-Recognition Performance of Adults With Cochlear Implants

et al. 2013

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Section: Effect Of Cochlear Implant Input Processing On Performance Wmentioning

confidence: 99%

Effects of Input Processing and Type of Personal Frequency Modulation System on Speech-Recognition Performance of Adults With Cochlear Implants

et al. 2013

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“…The term “ASC” was retained to refer to the slow stage of the dual-loop AGC, which has the same time constants as the earlier ASC implementation. Both ASC implementations have been shown to substantially improve speech intelligibility in noise [29], [30].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Automatic Gain Control Structure and Release Time on Cochlear Implant Speech Intelligibility

2013

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Nucleus cochlear implant systems incorporate a fast-acting front-end automatic gain control (AGC), sometimes called a compression limiter. The objective of the present study was to determine the effect of replacing the front-end compression limiter with a newly proposed envelope profile limiter. A secondary objective was to investigate the effect of AGC speed on cochlear implant speech intelligibility. The envelope profile limiter was located after the filter bank and reduced the gain when the largest of the filter bank envelopes exceeded the compression threshold. The compression threshold was set equal to the saturation level of the loudness growth function (i.e. the envelope level that mapped to the maximum comfortable current level), ensuring that no envelope clipping occurred. To preserve the spectral profile, the same gain was applied to all channels. Experiment 1 compared sentence recognition with the front-end limiter and with the envelope profile limiter, each with two release times (75 and 625 ms). Six implant recipients were tested in quiet and in four-talker babble noise, at a high presentation level of 89 dB SPL. Overall, release time had a larger effect than the AGC type. With both AGC types, speech intelligibility was lower for the 75 ms release time than for the 625 ms release time. With the shorter release time, the envelope profile limiter provided higher group mean scores than the front-end limiter in quiet, but there was no significant difference in noise. Experiment 2 measured sentence recognition in noise as a function of presentation level, from 55 to 89 dB SPL. The envelope profile limiter with 625 ms release time yielded better scores than the front-end limiter with 75 ms release time. A take-home study showed no clear pattern of preferences. It is concluded that the envelope profile limiter is a feasible alternative to a front-end compression limiter.

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“…All subjects used the Advanced Combination Encoder program (McDermott et al, 1992;Vandali et al, 2000) with sound processing features Autosensitivity (Patrick et al, 2006) and Adaptive Dynamic Range Optimization (ADRO V R ) enabled (Blamey, 2005), the combination of which has provided beneficial outcomes for CI recipients when listening in noise (Wolfe et al, 2011). The C-sound pressure level (SPL) parameter was set to 75 dB for all subjects.…”

Section: A Subjectsmentioning

confidence: 99%

A beamformer post-filter for cochlear implant noise reduction

Hersbach

Grayden

Fallon

et al. 2013

The Journal of the Acoustical Society of America

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Cochlear implant users have limited ability to understand speech in noisy conditions. Signal processing methods to address this issue that use multiple microphones typically use beamforming to perform noise reduction. However, the effectiveness of the beamformer is diminished as the number of interfering noises increases and the acoustic environment becomes more diffuse. A multi-microphone noise reduction algorithm that aims to address this issue is presented in this study. The algorithm uses spatial filtering to estimate the signal-to-noise ratio (SNR) and attenuates time-frequency elements that have poor SNR. The algorithm was evaluated by measuring intelligibility of speech embedded in 4-talker babble where the interfering talkers were spatially separated and changed location during the test. Twelve cochlear implant users took part in the evaluation, which demonstrated a significant mean improvement of 4.6 dB (standard error 0.4, P < 0.001) in speech reception threshold compared to an adaptive beamformer. The results suggest that a substantial improvement in performance can be gained for cochlear implant users in noisy environments where the noise is spatially separated from the target speech.

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The Effect of Front-End Processing on Cochlear Implant Performance of Children

Cited by 33 publications

References 18 publications

Effects of Input Processing and Type of Personal Frequency Modulation System on Speech-Recognition Performance of Adults With Cochlear Implants

Effects of Input Processing and Type of Personal Frequency Modulation System on Speech-Recognition Performance of Adults With Cochlear Implants

The Effect of Automatic Gain Control Structure and Release Time on Cochlear Implant Speech Intelligibility

A beamformer post-filter for cochlear implant noise reduction

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