A Psychoacoustic "NofM"-Type Speech Coding Strategy for Cochlear Implants

Nogueira, Waldo; Büchner, Andreas; Lenarz, Thomas; Edler, Bernd

doi:10.1155/asp.2005.3044

Cited by 92 publications

(82 citation statements)

References 22 publications

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“…Table 3 shows strategies that are currently being evaluated in company-sponsored studies. These strategies include "Fine Hearing" (Hochmair et al, 2006;Arnoldner et al, 2007), HiRes with the "Fidelity™ 120 option" (or "HiRes 120" for short) (Trautwein, 2006;Buechner et al, 2008;Litvak et al, 2008), and MP3000 (Nogueira et al, 2005;. The Fine Hearing strategy also is called the fine structure processing (FSP) strategy, and the MP3000 strategy also is called the psychoacoustic advanced combination encoder (PACE) strategy.…”

Section: Processing Strategies For Cochlear Implantsmentioning

confidence: 99%

Cochlear implants: A remarkable past and a brilliant future

2008

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The aims of this paper are to (i) provide a brief history of cochlear implants; (ii) present a status report on the current state of implant engineering and the levels of speech understanding enabled by that engineering; (iii) describe limitations of current signal processing strategies and (iv) suggest new directions for research. With current technology the "average" implant patient, when listening to predictable conversations in quiet, is able to communicate with relative ease. However, in an environment typical of a workplace the average patient has a great deal of difficulty. Patients who are "above average" in terms of speech understanding, can achieve 100% correct scores on the most difficult tests of speech understanding in quiet but also have significant difficulty when signals are presented in noise. The major factors in these outcomes appear to be (i) a loss of low-frequency, fine structure information possibly due to the envelope extraction algorithms common to cochlear implant signal processing; (ii) a limitation in the number of effective channels of stimulation due to overlap in electric fields from electrodes, and (iii) central processing deficits, especially for patients with poor speech understanding. Two recent developments, bilateral implants and combined electric and acoustic stimulation, have promise to remediate some of the difficulties experienced by patients in noise and to reinstate low-frequency fine structure information. If other possibilities are realized, e.g., electrodes that emit drugs to inhibit cell death following trauma and to induce the growth of neurites toward electrodes, then the future is very bright indeed.

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Section: Processing Strategies For Cochlear Implantsmentioning

confidence: 99%

Cochlear implants: A remarkable past and a brilliant future

2008

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“…Finally, the weights g L (k) are gain factors needed to equalize different effects introduced by the filterbank. For further details on numerical values of the parameters N b (k), l i (k) and g L (k), see [3].…”

Section: A Long and Short Filterbanksmentioning

confidence: 99%

“…Such limitations are most effectively addressed by "NofM" strategies, such as the Advanced Combinational Encoder (ACE) or the Psychoacoustical ACE [3]. Here the signals are decomposed into M channels, but only the N most meaningful bands are selected for each cycle stimulation.…”

Section: Introductionmentioning

confidence: 99%

Signal analysis by using adaptive filterbanks in cochlear implants

Albalate

Nogueira²,

Edler³

et al. 2006

2006 IEEE Biomedical Circuits and Systems Conference

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Abstract-Current speech processing in cochlear implants use a filterbank to analyse audio signals into several frequency bands, each associated with one electrode. Because the processing is performed on input signal blocks of fixed sizes, the filterbank provides a unique time-frequency resolution to represent the various signal features. However, different components of audio signals may require different time-frequency resolutions for an accurate representation and perception. In this paper we investigate the influence on speech intelligibility in cochlear implants users when filterbanks with different time-frequency resolutions are used. In order to represent all signal features accurately, an adaptive filterbank has been developed that accepts input blocks of different sizes. The different resolutions required are achieved by adequately switching between block sizes depending on the input signal characteristics. The filterbank was incorporated into the commercial Advanced Combinational Encoder (ACE) and acutely tested on six cochlear implant recipients.

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“…A channel selection scheme based on a psychoacoustic model (similar to that adopted in MP3, e.g., see ISO/IEC, 1999) was proposed by Noguiera et al (2005). Their rationale was that amplitudes falling below the masking threshold ought to be discarded as inaudible.…”

Section: Introductionmentioning

confidence: 99%

Comparison of two channel selection criteria for noise suppression in cochlear implants

Hazrati

Loizou

2013

The Journal of the Acoustical Society of America

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The performance of current channel selection criteria used in cochlear implant (CI) devices (e.g., maximum selection criterion used in ACE) degrades significantly in the presence of noise. In noisy backgrounds, coding strategies that select the "right" channels for stimulation could potentially produce substantial improvements in intelligibility. In this study, the performance of two alternative channel selection criteria is assessed in terms of intelligibility and subjective quality with CI users in noise. The performance is compared against that of the maximum selection scheme employed in the ACE strategy (comparison is also made with the CIS strategy). Sentences were presented to seven CI users in speech weighted noise (À5, 0, and 5 dB SNR). Both channel selection criteria were implemented under ideal conditions where a priori knowledge of the target and masker was assumed. This was done to assess the full potential benefit of selecting the "right" channels for stimulation in noisy backgrounds. Substantial intelligibility improvement relative to the CI users' daily strategy (i.e., ACE or CIS) was achieved with the two different channel selection criteria under all noisy conditions considered. No significant difference in subjective quality of noisy speech processed by the two channel selection criteria was observed.

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A Psychoacoustic "NofM"-Type Speech Coding Strategy for Cochlear Implants

Cited by 92 publications

References 22 publications

Cochlear implants: A remarkable past and a brilliant future

Cochlear implants: A remarkable past and a brilliant future

Signal analysis by using adaptive filterbanks in cochlear implants

Comparison of two channel selection criteria for noise suppression in cochlear implants

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