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Δευτέρα 8 Οκτωβρίου 2018
Measuring relative vibrotactile spatial acuity: effects of tactor type, anchor points and tactile anisotropy.
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Measuring relative vibrotactile spatial acuity: effects of tactor type, anchor points and tactile anisotropy.
Exp Brain Res. 2018 Oct 06;:
Authors: Hoffmann R, Valgeirsdóttir VV, Jóhannesson ÓI, Unnthorsson R, Kristjánsson Á
Abstract
Vibrotactile displays can compensate for the loss of sensory function of people with permanent or temporary deficiencies in vision, hearing, or balance, and can augment the immersive experience in virtual environments for entertainment, or professional training. This wide range of potential applications highlights the need for research on the basic psychophysics of mechanisms underlying human vibrotactile perception. One key consideration when designing tactile displays is determining the minimal possible spacing between tactile motors (tactors), by empirically assessing the maximal throughput of the skin, or, in other words, vibrotactile spatial acuity. Notably, such estimates may vary by tactor type. We assessed vibrotactile spatial acuity in the lower thoracic region for three different tactor types, each mounted in a 4 × 4 array with center-to-center inter-tactor distances of 25 mm, 20 mm, and 10 mm. Seventeen participants performed a relative three-alternative forced-choice point localization task with successive tactor activation for both vertical and horizontal stimulus presentation. The results demonstrate that specific tactor characteristics (frequency, acceleration, contact area) significantly affect spatial acuity measurements, highlighting that the results of spatial acuity measurements may only apply to the specific tactors tested. Furthermore, our results reveal an anisotropy in vibrotactile perception, with higher spatial acuity for horizontal than for vertical stimulus presentation. The findings allow better understanding of vibrotactile spatial acuity and can be used for formulating guidelines for the design of tactile displays, such as regarding inter-tactor spacing, choice of tactor type, and direction of stimulus presentation.
PMID: 30293171 [PubMed - as supplied by publisher]
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Measuring relative vibrotactile spatial acuity: effects of tactor type, anchor points and tactile anisotropy.
| Related Articles |
Measuring relative vibrotactile spatial acuity: effects of tactor type, anchor points and tactile anisotropy.
Exp Brain Res. 2018 Oct 06;:
Authors: Hoffmann R, Valgeirsdóttir VV, Jóhannesson ÓI, Unnthorsson R, Kristjánsson Á
Abstract
Vibrotactile displays can compensate for the loss of sensory function of people with permanent or temporary deficiencies in vision, hearing, or balance, and can augment the immersive experience in virtual environments for entertainment, or professional training. This wide range of potential applications highlights the need for research on the basic psychophysics of mechanisms underlying human vibrotactile perception. One key consideration when designing tactile displays is determining the minimal possible spacing between tactile motors (tactors), by empirically assessing the maximal throughput of the skin, or, in other words, vibrotactile spatial acuity. Notably, such estimates may vary by tactor type. We assessed vibrotactile spatial acuity in the lower thoracic region for three different tactor types, each mounted in a 4 × 4 array with center-to-center inter-tactor distances of 25 mm, 20 mm, and 10 mm. Seventeen participants performed a relative three-alternative forced-choice point localization task with successive tactor activation for both vertical and horizontal stimulus presentation. The results demonstrate that specific tactor characteristics (frequency, acceleration, contact area) significantly affect spatial acuity measurements, highlighting that the results of spatial acuity measurements may only apply to the specific tactors tested. Furthermore, our results reveal an anisotropy in vibrotactile perception, with higher spatial acuity for horizontal than for vertical stimulus presentation. The findings allow better understanding of vibrotactile spatial acuity and can be used for formulating guidelines for the design of tactile displays, such as regarding inter-tactor spacing, choice of tactor type, and direction of stimulus presentation.
PMID: 30293171 [PubMed - as supplied by publisher]
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Redundant Information Is Sometimes More Beneficial Than Spatial Information to Understand Speech in Noise
Objectives: To establish a framework to unambiguously define and relate the different spatial effects in speech understanding: head shadow, redundancy, squelch, spatial release from masking (SRM), and so on. Next, to investigate the contribution of interaural time and level differences to these spatial effects in speech understanding and how this is influenced by the type of masking noise. Design: In our framework, SRM is uniquely characterized as a linear combination of head shadow, binaural redundancy, and binaural squelch. The latter two terms are combined into one binaural term, which we define as binaural contrast: a benefit of interaural differences. In this way, SRM is a simple sum of a monaural and a binaural term. We used the framework to quantify these spatial effects in 10 listeners with normal hearing. The participants performed speech intelligibility tasks in different spatial setups. We used head-related transfer functions to manipulate the presence of interaural time and level differences. We used three spectrally matched masker types: stationary speech-weighted noise, a competing talker, and speech-weighted noise that was modulated with the broadband temporal envelope of the competing talker. Results: We found that (1) binaural contrast was increased by interaural time differences, but reduced by interaural level differences, irrespective of masker type, and (2) large redundancy (the benefit of having identical information in two ears) could reduce binaural contrast and thus also reduce SRM. Conclusions: Our framework yielded new insights in binaural processing in speech intelligibility. First, interaural level differences disturb speech intelligibility in realistic listening conditions. Therefore, to optimize speech intelligibility in hearing aids, it is more beneficial to improve monaural signal-to-noise ratios rather than to preserve interaural level differences. Second, although redundancy is mostly ignored when considering spatial hearing, it might explain reduced SRM in some cases. ACKNOWLEDGMENTS: This research is funded by the Research Foundation—Flanders (SB PhD fellow at FWO), project 1S45817N; this research is jointly funded by Cochlear Ltd. and Flanders Innovation & Entrepreneurship (formerly IWT), project 150432; this project has also received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 637424, ERC starting Grant to Tom Francart). We thank our participants for their patience and enthusiasm during our experiment. Benjamin Dieudonné and Tom Francart designed experiments, analyzed data, and wrote the article. Benjamin Dieudonné performed experiments. The authors have no conflicts of interest to disclose. Address for correspondence: Tom Francart, Experimental Oto-rhino-laryngology, Department of Neurosciences, KU Leuven, University of Leuven, Herestraat 49 bus 721, 3000 Leuven, Belgium. E-mail: tom.francart@med.kuleuven.be, benjamin.dieudonne@med.kuleuven.be Received February 15, 2018; accepted August 6, 2018. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
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Factors Affecting Sound-Source Localization in Children With Simultaneous or Sequential Bilateral Cochlear Implants
Objectives: The study aimed to determine the effect of interimplant interval and onset of profound deafness on sound localization in children with bilateral cochlear implants, controlling for cochlear implant manufacturer, age, and time since second implant. Design: The authors conducted a retrospective, observational study using routinely collected clinical data. Participants were 127 bilaterally implanted children aged 4 years or older, tested at least 12 mo post- second implant. Children used implants made by one of three manufacturers. Sixty-five children were simultaneously implanted, of whom 43% were congenitally, bilaterally profoundly deaf at 2 and 4 kHz and 57% had acquired or progressive hearing loss. Sixty-two were implanted sequentially (median interimplant interval = 58 mo, range 3–143 mo) of whom 77% had congenital and 23% acquired or progressive bilateral profound deafness at 2 and 4 kHz. Children participated in a sound-source localization test with stimuli presented in a random order from five loudspeakers at –60, –30, 0, +30, and +60 degrees azimuth. Stimuli were prerecorded female voices at randomly roved levels from 65 to 75 dB(A). Root mean square (RMS) errors were calculated. Localization data were analyzed via multivariable linear regression models, one applied to the whole group and the other to just the simultaneously\ implanted children. Results: Mean RMS error was 25.4 degrees (SD = 12.5 degrees) with results ranging from perfect accuracy to chance level (0–62.7 degrees RMS error). Compared with simultaneous implantation, an interimplant interval was associated with worse localization by 1.7 degrees RMS error per year (p
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Redundant Information Is Sometimes More Beneficial Than Spatial Information to Understand Speech in Noise
Objectives: To establish a framework to unambiguously define and relate the different spatial effects in speech understanding: head shadow, redundancy, squelch, spatial release from masking (SRM), and so on. Next, to investigate the contribution of interaural time and level differences to these spatial effects in speech understanding and how this is influenced by the type of masking noise. Design: In our framework, SRM is uniquely characterized as a linear combination of head shadow, binaural redundancy, and binaural squelch. The latter two terms are combined into one binaural term, which we define as binaural contrast: a benefit of interaural differences. In this way, SRM is a simple sum of a monaural and a binaural term. We used the framework to quantify these spatial effects in 10 listeners with normal hearing. The participants performed speech intelligibility tasks in different spatial setups. We used head-related transfer functions to manipulate the presence of interaural time and level differences. We used three spectrally matched masker types: stationary speech-weighted noise, a competing talker, and speech-weighted noise that was modulated with the broadband temporal envelope of the competing talker. Results: We found that (1) binaural contrast was increased by interaural time differences, but reduced by interaural level differences, irrespective of masker type, and (2) large redundancy (the benefit of having identical information in two ears) could reduce binaural contrast and thus also reduce SRM. Conclusions: Our framework yielded new insights in binaural processing in speech intelligibility. First, interaural level differences disturb speech intelligibility in realistic listening conditions. Therefore, to optimize speech intelligibility in hearing aids, it is more beneficial to improve monaural signal-to-noise ratios rather than to preserve interaural level differences. Second, although redundancy is mostly ignored when considering spatial hearing, it might explain reduced SRM in some cases. ACKNOWLEDGMENTS: This research is funded by the Research Foundation—Flanders (SB PhD fellow at FWO), project 1S45817N; this research is jointly funded by Cochlear Ltd. and Flanders Innovation & Entrepreneurship (formerly IWT), project 150432; this project has also received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 637424, ERC starting Grant to Tom Francart). We thank our participants for their patience and enthusiasm during our experiment. Benjamin Dieudonné and Tom Francart designed experiments, analyzed data, and wrote the article. Benjamin Dieudonné performed experiments. The authors have no conflicts of interest to disclose. Address for correspondence: Tom Francart, Experimental Oto-rhino-laryngology, Department of Neurosciences, KU Leuven, University of Leuven, Herestraat 49 bus 721, 3000 Leuven, Belgium. E-mail: tom.francart@med.kuleuven.be, benjamin.dieudonne@med.kuleuven.be Received February 15, 2018; accepted August 6, 2018. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
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Factors Affecting Sound-Source Localization in Children With Simultaneous or Sequential Bilateral Cochlear Implants
Objectives: The study aimed to determine the effect of interimplant interval and onset of profound deafness on sound localization in children with bilateral cochlear implants, controlling for cochlear implant manufacturer, age, and time since second implant. Design: The authors conducted a retrospective, observational study using routinely collected clinical data. Participants were 127 bilaterally implanted children aged 4 years or older, tested at least 12 mo post- second implant. Children used implants made by one of three manufacturers. Sixty-five children were simultaneously implanted, of whom 43% were congenitally, bilaterally profoundly deaf at 2 and 4 kHz and 57% had acquired or progressive hearing loss. Sixty-two were implanted sequentially (median interimplant interval = 58 mo, range 3–143 mo) of whom 77% had congenital and 23% acquired or progressive bilateral profound deafness at 2 and 4 kHz. Children participated in a sound-source localization test with stimuli presented in a random order from five loudspeakers at –60, –30, 0, +30, and +60 degrees azimuth. Stimuli were prerecorded female voices at randomly roved levels from 65 to 75 dB(A). Root mean square (RMS) errors were calculated. Localization data were analyzed via multivariable linear regression models, one applied to the whole group and the other to just the simultaneously\ implanted children. Results: Mean RMS error was 25.4 degrees (SD = 12.5 degrees) with results ranging from perfect accuracy to chance level (0–62.7 degrees RMS error). Compared with simultaneous implantation, an interimplant interval was associated with worse localization by 1.7 degrees RMS error per year (p
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