Bilateral cochlear implants in children : clinical and methodological studies

A cochlear implant (CI) restores functional hearing in individuals with bilateral severe- to-profound sensorineural hearing loss. Despite hearing loss in both ears, CIs are usually provided unilaterally, excluding the alleged benefits associated with bilateral auditory stimulation. Recently, however, bilateral cochlear implantation is increasingly common, with the main objectives of enhancing sound localization abilities and speech recognition, particularly in the presence of background noise. Here, using a within-subject longitudinal design in a large clinical study sample of children using bilateral cochlear implants (BiCI), a large, sustained, and significant bilateral benefit in horizontal sound localization accuracy (SLA) was demonstrated. A significant bilateral benefit also existed in speech recognition in noise spatially separated from the target signal. Speech recognition in quiet, however, was comparable under BiCI and unilateral CI listening conditions. Parental reports corroborated behavioral findings. Yet, the bilateral benefit was not uniform across subjects, large intersubject variability existed both with BiCI and unilateral CI, and neither SLA, nor speech recognition performance, was restored to that found in children with normal hearing (NH). Clinically important, a significant improvement of horizontal SLA with increasing BiCI experience (21 percentage points per year) was demonstrated from onset of bilateral stimulation until about 3 years post bilateral implantation (r = -0.51, p < 0.0001, n = 66), with a very similar developmental rate observed intraindividually (mean of the individual slopes = 19 percentage points per year of BiCI experience, n = 21), suggesting an experience-driven maturation of SLA. Of further clinical importance, no relationship between SLA and age or age at implantations was found, albeit, improvements in SLA as a function of BiCI experience were faster, and the bilateral SLA benefit was larger, when bilateral implantation occurred before 4 years of age. In an attempt to accommodate measurements of spatial hearing to clinical requirements, a SLA method using objectively recorded gaze was developed. Pupil positions toward spatially distributed auditory and visual events were recorded using corneal reflection eye tracking technique. The spatial resolution of the methodology allowed detailed objective analyses of gaze patterns in NH listeners from 6 months of age. SLA was rapidly measured in children (age range = 29 – 157 weeks; mean = 168 seconds, n = 12) and adults (mean = 162 seconds, n = 8). Data showed immature SLA in children, with increasing performance as a function of age (r = -0.68, p = 0.015). Highly reliable results existed in adults, who revealed high SLA across the entire spatial range tested. The findings in this thesis have important methodological implications for the clinical management of children with CI, and provide valuable data which may be used in counseling prior to bilateral cochlear implantation. Moreover, the objective and rapid SLA methodology may aid clinicians at an early stage of the process of early intervention with cochlear implants and/or hearing aids in children with hearing loss

The effect of an active transcutaneous bone conduction device on spatial release from masking

Objective: The aim was to quantify the effect of the experimental active transcutaneous Bone Conduction Implant (BCI) on spatial release from masking (SRM) in subjects with bilateral or unilateral conductive and mixed hearing loss. Design: Measurements were performed in a sound booth with five loudspeakers at 0\ub0, +/−30\ub0 and +/−150\ub0 azimuth. Target speech was presented frontally, and interfering speech from either the front (co-located) or surrounding (separated) loudspeakers. SRM was calculated as the difference between the separated and the co-located speech recognition threshold (SRT). Study Sample: Twelve patients (aged 22–76 years) unilaterally implanted with the BCI were included. Results: A positive SRM, reflecting a benefit of spatially separating interferers from target speech, existed for all subjects in unaided condition, and for nine subjects (75%) in aided condition. Aided SRM was lower compared to unaided in nine of the subjects. There was no difference in SRM between patients with bilateral and unilateral hearing loss. In aided situation, SRT improved only for patients with bilateral hearing loss. Conclusions: The BCI fitted unilaterally in patients with bilateral or unilateral conductive/mixed hearing loss seems to reduce SRM. However, data indicates that SRT is improved or maintained for patients with bilateral and unilateral hearing loss, respectively

A pilot study on spatial hearing in children with congenital unilateral aural atresia

Despite normal hearing in one ear, individuals with congenital unilateral aural atresia may perceive difficulties in everyday listening conditions typically containing multiple sound sources. While previous work shows that intervention with bone conduction devices may aid spatial hearing for some children, testing conditions are often arranged to maximize any benefit and are not very similar to daily life. The benefit from amplification on spatial tasks has been found to vary between individuals, for reasons not entirely clear. This study has sought to expand on the limited knowledge on how children with unilateral aural atresia recognize speech masked by competing speech, and how horizontal sound localization accuracy is affected by the degree of unilateral hearing loss and by amplification using unilateral bone conduction devices when fitted before 3 years of age. In a within-subject, repeated measures design, including 11 children (mean age = 7.9 years), bone conduction hearing device (BCD) amplification did not negatively affect horizontal sound localization accuracy. The effect on speech recognition scores showed greater inter-individual variability. No benefit from amplification on a group level was found. There was no association between age at fitting and the benefit of the BCD. For children with poor unaided sound localization accuracy, there was a greater BCD benefit. Unaided localization accuracy increased as a function of decreasing hearing thresholds in the atretic ear. While it is possible that low sound levels in the atretic ear provided access to interaural localization cues for the children with the lowest hearing thresholds, the association has to be further investigated in a larger sample of children

The effect of simulated unilateral hearing loss on horizontal sound localization accuracy and recognition of speech in spatially separate competing speech

Unilateral hearing loss (UHL) occurs in 25% of cases of congenital sensorineural hearing loss. Due to the unilaterally reduced audibility associated with UHL, everyday demanding listening situations may be disrupted despite normal hearing in one ear. The aim of this study was to quantify acute changes in recognition of speech in spatially separate competing speech and sound localization accuracy, and relate those changes to two levels of temporary induced UHL (UHL 30 and UHL 43 ; suffixes denote the average hearing threshold across 0.5, 1, 2, and 4 kHz) for 8 normal-hearing adults. A within-subject repeated-measures design was used (normal binaural conditions, UHL 30 and UHL 43 ). The main outcome measures were the threshold for 40% correct speech recognition and the overall variance in sound localization accuracy quantified by an Error Index (0 = perfect performance, 1.0 = random performance). Distinct and statistically significant deterioration in speech recognition (2.0 dB increase in threshold, p &lt; 0.01) and sound localization (Error Index increase of 0.16, p &lt; 0.001) occurred in the UHL 30 condition. Speech recognition did not significantly deteriorate further in the UHL 43 condition (1.0 dB increase in speech recognition threshold, p &gt; 0.05), while sound localization was additionally impaired (Error Index increase of 0.33, p &lt; 0.01) with an associated large increase in individual variability. Qualitative analyses on a subject-by-subject basis showed that high-frequency audibility was important for speech recognition, while low-frequency audibility was important for horizontal sound localization accuracy. While the data might not be entirely applicable to individuals with long-standing UHL, the results suggest a need for intervention for mild-to-moderate UHL

A comparison of Ionic 2 versus React Native and Android in terms of performance, by comparing the performance of applications

Nowadays almost everyone has a smart phone. In addition, as more people use smart phones more applications are being developed for smart phones. Each operating system on the smart phone market has its own applications. Up until a few years ago, developers had to develop an exclusive application for each operating system in order to cover the whole market. A number of cross-platform frameworks have emerged. These frameworks enable developers to use one code base for every operating system. To be able to use most of the code for all platforms makes it easier to maintain and evolve the application. Two of the frameworks that allow cross-platform development are React Native and Ionic. The purpose and goal of the thesis is to evaluate if Ionic 2 is eligible to use as a cross-platform framework in terms of performance. The method used to achieve the goal is based on replication. An application made in React Native is replicated by using Ionic 2. The applications are then evaluated with focus on performance. The applications are evaluated using AndroidViewClient and Trepn profiler. AndriodViewClient is run outside of the OS of the Android device and can control the GUI of a device. AndroidViewClient is used to automate the tests. The metrics used for evaluating the performance are CPU load, memory usage, battery power usage, the size of the application and the size of the Android package kit. Trepn profiler is an application that is installed on the device. Trepn profiler has access to the hardware of the device and is therefore used to measure the first three mentioned metrics

A comparison of Ionic 2 versus React Native and Android in terms of performance, by comparing the performance of applications

Nowadays almost everyone has a smart phone. In addition, as more people use smart phones more applications are being developed for smart phones. Each operating system on the smart phone market has its own applications. Up until a few years ago, developers had to develop an exclusive application for each operating system in order to cover the whole market. A number of cross-platform frameworks have emerged. These frameworks enable developers to use one code base for every operating system. To be able to use most of the code for all platforms makes it easier to maintain and evolve the application. Two of the frameworks that allow cross-platform development are React Native and Ionic. The purpose and goal of the thesis is to evaluate if Ionic 2 is eligible to use as a cross-platform framework in terms of performance. The method used to achieve the goal is based on replication. An application made in React Native is replicated by using Ionic 2. The applications are then evaluated with focus on performance. The applications are evaluated using AndroidViewClient and Trepn profiler. AndriodViewClient is run outside of the OS of the Android device and can control the GUI of a device. AndroidViewClient is used to automate the tests. The metrics used for evaluating the performance are CPU load, memory usage, battery power usage, the size of the application and the size of the Android package kit. Trepn profiler is an application that is installed on the device. Trepn profiler has access to the hardware of the device and is therefore used to measure the first three mentioned metrics

A comparison of Ionic 2 versus React Native and Android in terms of performance, by comparing the performance of applications

Nowadays almost everyone has a smart phone. In addition, as more people use smart phones more applications are being developed for smart phones. Each operating system on the smart phone market has its own applications. Up until a few years ago, developers had to develop an exclusive application for each operating system in order to cover the whole market. A number of cross-platform frameworks have emerged. These frameworks enable developers to use one code base for every operating system. To be able to use most of the code for all platforms makes it easier to maintain and evolve the application. Two of the frameworks that allow cross-platform development are React Native and Ionic. The purpose and goal of the thesis is to evaluate if Ionic 2 is eligible to use as a cross-platform framework in terms of performance. The method used to achieve the goal is based on replication. An application made in React Native is replicated by using Ionic 2. The applications are then evaluated with focus on performance. The applications are evaluated using AndroidViewClient and Trepn profiler. AndriodViewClient is run outside of the OS of the Android device and can control the GUI of a device. AndroidViewClient is used to automate the tests. The metrics used for evaluating the performance are CPU load, memory usage, battery power usage, the size of the application and the size of the Android package kit. Trepn profiler is an application that is installed on the device. Trepn profiler has access to the hardware of the device and is therefore used to measure the first three mentioned metrics

Distributed certificates in ad hoc networks

In this report an ad hoc system is defined with the capabilities to validate the integrity ofevery node in the network without a third party, as long as every node has possession of acertificate. The system is developed to function in an ad hoc network with many externalthreats. The main target group would be the military and first responders. There are manydifferent problems with such a network, and many parts have been researched, but few fullsystems have been developed. This report defines a hierarchical system where nodes cancommunicate in an encrypted way, with the help of certificates. In a military situation therisk for compromised nodes must be considered. Therefore, the system can both detectand handle compromised nodes by revocation certificates. The proposed system is alsodetecting and handling partitions. The system has been put together by first making aliterature study to find existing solutions to different problems, then making a synthesisof those solutions. We also came up with new solutions where the three cornerstones ofsecurity: availability, confidentiality and integrity were in focus. To make the solutionmore trustworthy a risk analysis on the resulting system was made, which defined theweak points of the system

Моделирование инструментальной поверхности, формируемой сборной фрезой

Разработаны математические модели образующих инструментальных поверхностей, позволяющие определить шероховатость и топографию кинематических поверхностей. Эти модели позволяют также определить влияние геометрических параметров сменных многогранных пластин и их расположение в корпусе инструмента на вид и параметры образующей инструментальной поверхности

Horizontal sound localisation accuracy in individuals with conductive hearing loss: effect of the bone conduction implant

<p><b>Objective:</b> The objective of this study is to quantify the effect of the Bone Conduction Implant (BCI) on sound localisation accuracy in subjects with conductive hearing loss (CHL).</p> <p><b>Design:</b> The subjects were tested in a horizontal sound localisation task in which localisation responses were objectively obtained by eye-tracking, in a prospective, cross-sectional design. The tests were performed unaided and unilaterally aided. The stimulus used had a spectrum similar to female speech and was presented at 63 and 73 dB SPL. The main outcome measure was the error index (EI), ranging from 0 to 1 (perfect to random performance).</p> <p><b>Study sample:</b> Eleven subjects (aged 21–75 years, five females) with BCI participated in the study. Their mixed/conductive hearing loss was either unilateral (<i>n</i> = 5) or bilateral (<i>n</i> = 6).</p> <p><b>Results:</b> Three of five subjects (60%) with unilateral CHL, and four of six subjects (67%) with bilateral CHL showed significantly improved sound localisation when using a unilateral BCI (<i>p</i> < .05). For the subjects with bilateral CHL, a distinct linear relation between aided sound localisation and hearing thresholds in the non-implant ear existed at 73 dB SPL (18% decrease in the EI per 10 dB decrease in pure-tone average, <i>r</i> = 0.98, <i>p</i> < .001).</p> <p><b>Conclusions:</b> Individuals with mixed/conductive hearing loss may benefit from a unilateral BCI in sound localisation.</p