Pulse-spreading harmonic complex as an alternative carrier for vocoder simulations of cochlear implants

Mesnildrey, Quentin; Hilkhuysen, Gaston; Macherey, Olivier

doi:10.1121/1.4941451

Cited by 14 publications

(17 citation statements)

References 22 publications

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“…The PSHC carriers all had a fundamental frequency of 0.3 Hz. The PSHC pulse rate differed across bands and was a function of the center frequency of the corresponding synthesis bandpass filter following the equation in Figure 1 of Mesnildrey et al. (2016).…”

Section: Methodsmentioning

confidence: 99%

“…This equation provides the pulse rate yielding a minimum of intrinsic modulations after auditory filtering, given the center frequency of the synthesis filter. Similar to Mesnildrey et al. (2016), the cutoff frequency of the envelope extraction stage was equal to half the PSHC pulse rate in cases where it was lower than 200 Hz but was otherwise limited to 200 Hz to mimic the poor salience of temporal pitch cues experienced by CI listeners at high rates (e.g., Kong & Carlyon, 2010; Townshend, Cotter, Van Compernolle, & White, 1987).…”

Section: Methodsmentioning

confidence: 99%

“…There is a large number of parameters that may affect the sound quality of real and simulated CIs. These include (a) the number of physical electrode contacts, simulated by the number of vocoder channels (Faulkner, Rosen, & Wilkinson, 2001; Loizou & Dorman, 1999); (b) the amount of frequency mismatch due to the limited insertion of the electrode array, simulated by the frequency mismatch between the analysis and synthesis frequency ranges (James et al., 2018; Landsberger, Svrakic, Roland, & Svirsky, 2015; Rosen et al., 1999; Souza & Rosen, 2009); (c) the variations in current spread, simulated by the width of the synthesis bands (Bingabr, Espinoza-Varas, & Loizou, 2008; Crew & Galvin, 2012; Mesnildrey & Macherey, 2015; Oxenham & Kreft, 2014); (d) the extent of neural degeneration, simulated by the presence of holes in the vocoder frequency spectrum (Shannon, Galvin, & Baskent, 2002); and (e) the electrical stimulus waveform, simulated by the acoustic carrier waveform (Grange, Culling, Harris, & Bergfeld, 2017; Mesnildrey, Hilkhuysen, & Macherey, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Searching for the Sound of a Cochlear Implant: Evaluation of Different Vocoder Parameters by Cochlear Implant Users With Single-Sided Deafness

et al. 2019

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Cochlear implantation in subjects with single-sided deafness (SSD) offers a unique opportunity to directly compare the percepts evoked by a cochlear implant (CI) with those evoked acoustically. Here, nine SSD-CI users performed a forced-choice task evaluating the similarity of speech processed by their CI with speech processed by several vocoders presented to their healthy ear. In each trial, subjects heard two intervals: their CI followed by a certain vocoder in Interval 1 and their CI followed by a different vocoder in Interval 2. The vocoders differed either (i) in carrier type—(sinusoidal [SINE], bandfiltered noise [NOISE], and pulse-spreading harmonic complex) or (ii) in frequency mismatch between the analysis and synthesis frequency ranges—(no mismatch, and two frequency-mismatched conditions of 2 and 4 equivalent rectangular bandwidths [ERBs]). Subjects had to state in which of the two intervals the CI and vocoder sounds were more similar. Despite a large intersubject variability, the PSHC vocoder was judged significantly more similar to the CI than SINE or NOISE vocoders. Furthermore, the No-mismatch and 2-ERB mismatch vocoders were judged significantly more similar to the CI than the 4-ERB mismatch vocoder. The mismatch data were also interpreted by comparing spiral ganglion characteristic frequencies with electrode contact positions determined from postoperative computed tomography scans. Only one subject demonstrated a pattern of preference consistent with adaptation to the CI sound processor frequency-to-electrode allocation table and two subjects showed possible partial adaptation. Those subjects with adaptation patterns presented overall small and consistent frequency mismatches across their electrode arrays.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Searching for the Sound of a Cochlear Implant: Evaluation of Different Vocoder Parameters by Cochlear Implant Users With Single-Sided Deafness

et al. 2019

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“…It is also worth noting that the listeners in the CI simulation experiment showed a greater MPB than the CI users despite the use of a noise-excited vocoder simulation. The inherent random modulations of a noise carrier are known to make it more difficult to detect a target modulation (Dau et al, 1997) and in line with this, CI simulations using tone-vocoders (Whitmal III et al, 2007) and pulse-spreading harmonic complexes (Mesnildrey et al, 2016) have reported better speech perception in the presence of a masker. Accordingly, using these types of carriers would likely resulted in an even larger MPB.…”

Section: B Masker-periodicity Benefitmentioning

confidence: 80%

The role of envelope periodicity in the perception of masked speech with simulated and real cochlear implants

Steinmetzger

Rosen

2018

The Journal of the Acoustical Society of America

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In normal hearing, complex tones with pitch-related periodic envelope modulations are far less effective maskers of speech than aperiodic noise. Here, it is shown that this is diminished in noise-vocoder simulations of cochlear implants (CIs) and further reduced with real CIs. Nevertheless, both listener groups still benefitted significantly from masker periodicity, despite the lack of salient spectral pitch cues. The main reason for the smaller effect observed in CI users is thought to be an even stronger channel interaction than in the CI simulations, which smears out the random envelope modulations that are characteristic for aperiodic sounds. In contrast, neither interferers that were amplitude-modulated at a rate of 10 Hz nor maskers with envelopes specifically designed to reveal the target speech enabled a masking release in CI users. Hence, even at the high signal-to-noise ratios at which they were tested, CI users can still exploit pitch cues transmitted by the temporal envelope of a non-speech masker, whereas slow amplitude modulations of the masker envelope are no longer helpful.

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“…Simulations with less than eight channels presented to normal-hearing listeners provide speech intelligibility scores in the same range as CI patients [1], [2]. Despite this good result, some researchers argue that the vocoded information does not offer the same sound quality as that of CIs and suggest the existence of perceptual and informational discrepancies between CI stimulation and performance-matched acoustical simulations [3][4][5][6]. Thus, a similar level of performance obtained for both real and simulated CI may hide different patterns of errors, limiting the validity of acoustic simulations through vocoders to evaluate new coding strategies.…”

Section: Introductionmentioning

confidence: 99%

The sound sensation of a pure tone in cochlear implant recipients with single-sided deafness

Marozeau

Gnansia²,

Ardoint³

et al. 2020

PLoS ONE

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Ten cochlear implant (CI) users with single-sided deafness were asked to vary the parameters of an acoustic sound played to their contralateral ear to characterize the perception evoked by a pure tone played through the direct audio input of their CI. Two frequencies, centered on an apical and a medial electrode, were tested. In six subjects, the electrode positions were estimated on CT scans. The study was divided in 3 experiments in which the parameters of the acoustic sound varied. The listeners had to vary the frequency of a pure tone (Exp.1), the center frequency and the bandwidth of a filter applied to a harmonic complex sound (Exp.2), and the frequency of the components and the inharmonicity factor of a complex sound (Exp.3). Two testing sessions were performed at 3 and 12 months after activation. The mean results of Exp. 1 showed that the frequency of the matched tone was significantly lower for the apical than for the medial stimulus. In Exp.2, the mean center frequencies of the filters were also significantly lower for the apical than for the medial stimulus. As this parameter modifies the energy ratio between the high and low-frequency components, this result suggests that the medial stimulus was perceived with a brighter timbre than the apical stimulus. In Exp.3, the mean frequencies of the components were not significantly different between the sounds resulting from the stimulation of the two electrodes, but were significantly lower at the12-month session compared to the 3-month visit. These results suggest that a change in place of excitation may be perceived as a change in timbre rather than a change in pitch, and that an effect of adaptation can be observed.

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Pulse-spreading harmonic complex as an alternative carrier for vocoder simulations of cochlear implants

Cited by 14 publications

References 22 publications

Searching for the Sound of a Cochlear Implant: Evaluation of Different Vocoder Parameters by Cochlear Implant Users With Single-Sided Deafness

Searching for the Sound of a Cochlear Implant: Evaluation of Different Vocoder Parameters by Cochlear Implant Users With Single-Sided Deafness

The role of envelope periodicity in the perception of masked speech with simulated and real cochlear implants

The sound sensation of a pure tone in cochlear implant recipients with single-sided deafness

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