Real-time loudness normalisation with combined cochlear implant and hearing aid stimulation

Spirrov, Dimitar; Eeckhoutte, Maaike Van; Deun, Lieselot Van; Francart, Tom

doi:10.1371/journal.pone.0195412

Cited by 4 publications

(5 citation statements)

References 39 publications

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“…This suggests that compression itself may balance the perceived loudness across the ears, reducing hearing asymmetry at least for some individuals. In fact, spatial hearing in bimodal users has been demonstrated to improve by conventional (without frequency compression) loudness balancing (Francart et al, 2008;Spirrov et al, 2018;Van Eeckhoutte, Spirrov et al, 2018;. However, the amount of bias shift in our study was only partially explained by the benefit in high-frequency audibility provided by compression (see Figure 7B) and sound localization was still erroneous (see Figures 6A-6C).…”

Section: The Effect Of Compression On Sound Localizationcontrasting

confidence: 53%

Amount of Frequency Compression in Bimodal Cochlear Implant Users Is a Poor Predictor for Audibility and Spatial Hearing

Sharma

Nogueira

Opstal

et al. 2021

J Speech Lang Hear Res

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Purpose Speech understanding in noise and horizontal sound localization is poor in most cochlear implant (CI) users with a hearing aid (bimodal stimulation). This study investigated the effect of static and less-extreme adaptive frequency compression in hearing aids on spatial hearing. By means of frequency compression, we aimed to restore high-frequency audibility, and thus improve sound localization and spatial speech recognition. Method Sound-detection thresholds, sound localization, and spatial speech recognition were measured in eight bimodal CI users, with and without frequency compression. We tested two compression algorithms: a static algorithm, which compressed frequencies beyond the compression knee point (160 or 480 Hz), and an adaptive algorithm, which aimed to compress only consonants leaving vowels unaffected (adaptive knee-point frequencies from 736 to 2946 Hz). Results Compression yielded a strong audibility benefit (high-frequency thresholds improved by 40 and 24 dB for static and adaptive compression, respectively), no meaningful improvement in localization performance (errors remained > 30 deg), and spatial speech recognition across all participants. Localization biases without compression (toward the hearing-aid and implant side for low- and high-frequency sounds, respectively) disappeared or reversed with compression. The audibility benefits provided to each bimodal user partially explained any individual improvements in localization performance; shifts in bias; and, for six out of eight participants, benefits in spatial speech recognition. Conclusions We speculate that limiting factors such as a persistent hearing asymmetry and mismatch in spectral overlap prevent compression in bimodal users from improving sound localization. Therefore, the benefit in spatial release from masking by compression is likely due to a shift of attention to the ear with the better signal-to-noise ratio facilitated by compression, rather than an improved spatial selectivity. Supplemental Material https://doi.org/10.23641/asha.16869485

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Section: The Effect Of Compression On Sound Localizationcontrasting

confidence: 53%

Amount of Frequency Compression in Bimodal Cochlear Implant Users Is a Poor Predictor for Audibility and Spatial Hearing

Sharma

Nogueira

Opstal

et al. 2021

J Speech Lang Hear Res

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“…Given that previous studies have not demonstrated any influence of loudness matching on speech recognition in quiet ( Dorman et al., 2014b ; Spirrov et al., 2018 ) or in noise ( Spirrov et al., 2018 ), we hypothesized that the specific effect found by Veugen et al. (2016a) was mostly driven by the time constants alone and not by the particular matching of the AGCs.…”

mentioning

confidence: 86%

“…Given that previous studies have not demonstrated any influence of loudness matching on speech recognition in quiet (Dorman et al, 2014b;Spirrov et al, 2018) or in noise (Spirrov et al, 2018), we hypothesized that the specific effect found by Veugen et al (2016a) was mostly driven by the time constants alone and not by the particular matching of the AGCs. Given that the results were only specified as bimodal benefit (bimodal-CI-only speech recognition), we hypothesize that the effect was not bimodal but rather monaural.…”

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confidence: 97%

Effect of (Mis)Matched Compression Speed on Speech Recognition in Bimodal Listeners

et al. 2020

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Automatic gain control (AGC) compresses the wide dynamic range of sounds to the narrow dynamic range of hearing-impaired listeners. Setting AGC parameters (time constants and knee points) is an important part of the fitting of hearing devices. These parameters do not only influence overall loudness elicited by the hearing devices but can also affect the recognition of speech in noise. We investigated whether matching knee points and time constants of the AGC between the cochlear implant and the hearing aid of bimodal listeners would improve speech recognition in noise. We recruited 18 bimodal listeners and provided them all with the same cochlear-implant processor and hearing aid. We compared the matched AGCs with the default device settings with mismatched AGCs. As a baseline, we also included a condition with the mismatched AGCs of the participants’ own devices. We tested speech recognition in quiet and in noise presented from different directions. The time constants affected outcomes in the monaural testing condition with the cochlear implant alone. There were no specific binaural performance differences between the two AGC settings. Therefore, the performance was mostly dependent on the monaural cochlear implant alone condition.

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“…To conclude, these results might partly shift the focus and interpretation of bimodal signal processing strategies. While loudness balance (Francart & Mcdermott, 2012;Spirrov et al, 2018) and binaural cue preservation/enhancement (Francart et al, , 2014 are important for listening comfort and sound localization, their influence on speech perception is probably minor. Instead, to improve speech perception, it is the simplest and probably most efficient to focus on monaural sound quality (e.g., audibility, SNR, minimal distortion, etc.)…”

Section: Clinical Relevancementioning

confidence: 99%

Speech Understanding With Bimodal Stimulation Is Determined by Monaural Signal to Noise Ratios: No Binaural Cue Processing Involved

Dieudonné

Francart

2020

Ear &Amp; Hearing

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Objectives: To investigate the mechanisms behind binaural and spatial effects in speech understanding for bimodal cochlear implant listeners. In particular, to test our hypothesis that their speech understanding can be characterized by means of monaural signal-to-noise ratios, rather than complex binaural cue processing such as binaural unmasking. Design:We applied a semantic framework to characterize binaural and spatial effects in speech understanding on an extensive selection of the literature on bimodal listeners. In addition, we performed two experiments in which we measured speech understanding in different masker types(1) using head-related transfer functions, and (2) while adapting the broadband signal-to-noise ratios in both ears independently. We simulated bimodal hearing with a vocoder in one ear (the cochlear implant side) and a low pass filter in the other ear (the hearing aid side). By design, the cochlear implant side was the main contributor to speech understanding in our simulation. Results:We found that spatial release from masking can be explained as a simple trade-off between a monaural change in signal-to-noise at the cochlear implant side (quantified as the head shadow effect) and an opposite change in signal-to-noise at the hearing aid side (quantified as a change in bimodal benefit). In simulated bimodal listeners, we found that for every 1 dB increase in signalto-noise ratio at the hearing aid side, the bimodal benefit improved by approximately 0.4 dB in signal-to-noise ratio. Conclusions:Although complex binaural cue processing is often implicated when discussing speech intelligibility in adverse listening conditions, performance can simply be explained based on monaural signal-to-noise ratios for bimodal listeners.

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Real-time loudness normalisation with combined cochlear implant and hearing aid stimulation

Cited by 4 publications

References 39 publications

Amount of Frequency Compression in Bimodal Cochlear Implant Users Is a Poor Predictor for Audibility and Spatial Hearing

Amount of Frequency Compression in Bimodal Cochlear Implant Users Is a Poor Predictor for Audibility and Spatial Hearing

Effect of (Mis)Matched Compression Speed on Speech Recognition in Bimodal Listeners

Speech Understanding With Bimodal Stimulation Is Determined by Monaural Signal to Noise Ratios: No Binaural Cue Processing Involved

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