487 research outputs found
Improvement of Speech Perception for Hearing-Impaired Listeners
Hearing impairment is becoming a prevalent health problem affecting 5% of world adult populations. Hearing aids and cochlear implant already play an essential role in helping patients over decades, but there are still several open problems that prevent them from providing the maximum benefits. Financial and discomfort reasons lead to only one of four patients choose to use hearing aids; Cochlear implant users always have trouble in understanding speech in a noisy environment.
In this dissertation, we addressed the hearing aids limitations by proposing a new hearing aid signal processing system named Open-source Self-fitting Hearing Aids System (OS SF hearing aids). The proposed hearing aids system adopted the state-of-art digital signal processing technologies, combined with accurate hearing assessment and machine learning based self-fitting algorithm to further improve the speech perception and comfort for hearing aids users. Informal testing with hearing-impaired listeners showed that the testing results from the proposed system had less than 10 dB (by average) difference when compared with those results obtained from clinical audiometer. In addition, Sixteen-channel filter banks with adaptive differential microphone array provides up to six-dB SNR improvement in the noisy environment. Machine-learning based self-fitting algorithm provides more suitable hearing aids settings.
To maximize cochlear implant usersâ speech understanding in noise, the sequential (S) and parallel (P) coding strategies were proposed by integrating high-rate desynchronized pulse trains (DPT) in the continuous interleaved sampling (CIS) strategy. Ten participants with severe hearing loss participated in the two rounds cochlear implants testing. The testing results showed CIS-DPT-S strategy significantly improved (11%) the speech perception in background noise, while the CIS-DPT-P strategy had a significant improvement in both quiet (7%) and noisy (9%) environment
Wireless body sensor networks for health-monitoring applications
This is an author-created, un-copyedited version of an article accepted for publication in
Physiological Measurement. The publisher is
not responsible for any errors or omissions in this version of the manuscript or any version
derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0967-3334/29/11/R01
Analysis and Design of RF Power and Data Link Using Amplitude Modulation of Class-E for a Novel Bone Conduction Implant
This paper presents analysis and design of a radio frequency power and data link for a novel Bone Conduction Implant (BCI) system. Patients with conductive and mixed hearing loss and single-sided deafness can be rehabilitated by bone-anchored hearing aids (BAHA). Whereas the conventional hearing aids transmit sound to the tympanic membrane via air conduction, the BAHA transmits sound via vibrations through the skull directly to the cochlea. It uses a titanium screw that penetrates the skin and needs life-long daily care; it may cause skin infection and redness. The BCI is developed as an alternative to the percutaneous BAHA since it leaves the skin intact. The BCI comprises an external audio processor with a transmitter coil and an implanted unit called the bridging bone conductor with a receiver coil. Using amplitude modulation of the Class-E power amplifier that drives the inductive link, the sound signal is transmitted to the implant through the intact skin. It was found that the BCI can generate enough output force level for candidate patients. Maximum power output of the BCI was designed to occur at 5-mm skin thickness and the variability was within 1.5 dB for 1â8-mm skin thickness variations
Determination and evaluation of clinically efficient stopping criteria for the multiple auditory steady-state response technique
Background: Although the auditory steady-state response (ASSR) technique utilizes objective statistical detection algorithms to estimate behavioural hearing thresholds, the audiologist still has to decide when to terminate ASSR recordings introducing once more a certain degree of subjectivity.
Aims: The present study aimed at establishing clinically efficient stopping criteria for a multiple 80-Hz ASSR system.
Methods: In Experiment 1, data of 31 normal hearing subjects were analyzed off-line to propose stopping rules. Consequently, ASSR recordings will be stopped when (1) all 8 responses reach significance and significance can be maintained for 8 consecutive sweeps; (2) the mean noise levels were †4 nV (if at this â†4-nVâ criterion, p-values were between 0.05 and 0.1, measurements were extended only once by 8 sweeps); and (3) a maximum amount of 48 sweeps was attained. In Experiment 2, these stopping criteria were applied on 10 normal hearing and 10 hearing-impaired adults to asses the efficiency.
Results: The application of these stopping rules resulted in ASSR threshold values that were comparable to other multiple-ASSR research with normal hearing and hearing-impaired adults. Furthermore, in 80% of the cases, ASSR thresholds could be obtained within a time-frame of 1 hour. Investigating the significant response-amplitudes of the hearing-impaired adults through cumulative curves indicated that probably a higher noise-stop criterion than â†4 nVâ can be used.
Conclusions: The proposed stopping rules can be used in adults to determine accurate ASSR thresholds within an acceptable time-frame of about 1 hour. However, additional research with infants and adults with varying degrees and configurations of hearing loss is needed to optimize these criteria
Neural Correlates of Binaural Interaction Using Aggregate-System Stimulation in Cochlear Implantees
The importance of binaural cues in auditory stream formation and sound source diïŹerentiation is widely accepted. When treating one ear with a cochlear implant (CI) the peripheral auditory system gets partially replaced and processing delays get added potentially, thus important interaural time encoding gets altered. This is a crucial problem because factors like the interaural time delay between the receiving ears are known to be responsible for facilitating such cues, e.g., sound source localization and separation. However, these eïŹects are not fully understood, leaving a lack of systematic binaural ïŹtting strategies with respect to an optimal binaural fusion.
To gain new insights into such alterations, we suggest a novel method of free-ïŹeld evoked auditory brainstem response (ABR) analysis in CI users. As a result, this method does not bypass the technically induced intrinsic delays of the hearing device while leaving the complete electrode array active, thus the most natural way of stimulation is provided and the comparable testing of real world stimuli gets facilitated. Unfortunately, ABRs acquired in CI users are additionally aïŹected by the prominent artifact caused by their electrical stimulation, which severely distorts the desired neural response, thus challenging their analysis. To circumvent this problem, we further introduce a novel narrowband ïŹltering CI artifact removal technique capable of obtaining neural correlates of ABRs in CI users. Consequently, we were able to compare brainstem-level responses collected of 12 CI users and 12 normal hearing listeners using two diïŹerent stimuli (i.e., chirp and click) at four diïŹerent intensities each, what comprises an adaption of the prominent brainstem evoked response audiometry serving as an additional evaluation criterion. We analyzed the responses using the average of 2,000 trials in combination with synchronized regularizations across them and found consistent results in their deïŹections and latencies, as well as in single trial relationships between both groups. This method provides a novel and unique perspective into the natural CI usersâ brainstem-level responses and can be practical in future research regarding binaural interaction and fusion. Furthermore, the binaural interaction component (BIC), i.e., the arithmetical diïŹerence between the sum of both monaurally evoked ABRs and the binaurally evoked ABR, has been previously shown to be an objective indicator for binaural interaction. This component is unfortunately known to be rather fragile and as a result, a reliable, objective measure of binaural interaction in CI users does not exist to the present date. It is most likely that implantees would beneïŹt from a reliable analysis of brainstem-level and subsequent higher-level binaural interaction, since this could objectively support ïŹtting strategies with respect to a maximization of interaural integration. Therefore, we introduce a novel method capable of obtaining neural correlates of binaural interaction in bimodal CI users by combining recent advances in the ïŹeld of fast, deconvolution-based ABR acquisitions with the introduced narrowband ïŹltering technique. The proposed method shows a signiïŹcant improvement in the magnitude of resulting BICs in 10 bimodal CI users and a control-group of 10 normal hearing subjects when compensating the interaural latency diïŹerence caused by the technical devices.
In total, both proposed studies objectively demonstrate technical-driven interaural latency mismatches. Thus, they strongly emphasize potential beneïŹts when balancing these interaural delays to improve binaural processing by signiïŹcant increases in associated neural correlates of successful binaural interaction. These results and also the estimated latency diïŹerences should be investigated in larger group sizes to further consolidate the results, but conïŹrm the demand for rather binaural solutions than treating hearing losses in an isolated monaural manner.Zusammenfassung
Die Notwendigkeit binauraler Verarbeitungsprozesse in der auditorischen
Wahrnehmung ist weitestgehend akzeptiert. Bei der Therapie eines Ohres
mit einem Cochlea-Implantat (engl. cochlear implant (CI)) wird das periphere
auditorische System teilweise ersetzt und verĂ€ndert, sodass natĂŒrliche, interaurale
Zeitauflösungen beeinflusst werden. Dieses Problem ist entscheidend, denn Faktoren
wie interaurale Laufzeitunterschiede zwischen den aufnehmenden Ohren sind
verantwortlich fĂŒr die Umsetzung der erwĂ€hnten binauralen Verarbeitungsprozesse,
z.B. Schallquellenlokalisation und -separation. Allerdings sind diese Effekte
nicht ausreichend verstanden, weshalb bis heute binaurale Anpassstrategien mit
RĂŒcksicht auf eine optimale Fusionierung fehlen.
Um neue Einsichten in solche zeitlichen Verzerrungen zu erhalten, schlagen
wir ein neues Verfahren der Freifeld evozierten auditorischen Hirnstammpotentiale
(engl. auditory brainstem response (ABR)) in CI-Nutzern vor. Diese Methode
beinhaltet explizit technisch-induzierte Laufzeiten verwendeter Hörhilfen,
sodass eine natĂŒrliche Stimulation unter Verwendung von realitĂ€tsnahen Stimuli
ermöglicht wird. UnglĂŒcklicherweise sind ABRs von CI-Nutzern zusĂ€tzlich mit
Stimulationsartefakten belastet, wodurch benötigte neurale Antworten weiter
verzerrt werden und eine entsprechende Analyse der Signale deutlich erschwert
wird. Um dieses Problem zu umgehen, schlagen wir eine neue Artefakt-
Reduktionstechnik vor, welche auf spektraler Schmalbandfilterung basiert und
somit den Erhalt entsprechender, neuraler ABR Korrelate ermöglicht. Diese
Methoden erlaubten die Interpretation neuraler Korrelate auf Hirnstammebene
unter Verwendung von zwei verschiedenen Stimuli (Chirps und Klicks) unter vier
verschiedenen LautstÀrken in 12 CI-Nutzern und 12 normalhörenden Probanden.
Die beschriebene Prozedur adaptiert somit die weitlÀufig bekannte Hirnstammaudiometrie
(engl. brainstem evoked response audiometry (BERA)), deren Ergebnisse
zur zusÀtzlichen Evaluation des vorgestellten Verfahrens dienten. Die Untersuchung
der aus 2000 Einzelantworten erhaltenen Mittelwerte in Kombination mit der
Analyse synchronisierter RegularitĂ€ten ĂŒber den Verlauf der Einzelantworten ergab
dabei konsistente Beobachtungen in gefundenen Amplituden, Latenzen sowie in
AbhÀngigkeiten zwischen Einzelantworten in beiden Gruppen. Das vorgestellte
Verfahren erlaubt somit auf einzigartige Weise neue und ungesehene Einsichten
in natĂŒrliche, neurale Antworten auf Hirnstammebene von CI-Nutzern, welche
in zukĂŒnftigen Studien verwendet werden können, um binaurale Interaktionen
und Fusionen weiter untersuchen zu können. Interessanterweise hat sich, die auf
ABRs basierende, binaurale Interaktionskomponente (engl. binaural interaction
component (BIC)) als objektiver Indikator binauraler Integration etabliert. Diese
Komponente (d.h. die arithmetische Differenz zwischen der Summe der monauralen
Antworten und der binauralen Antwort) ist leider sehr fragil, wodurch ein sicherer
und objektiver Nachweis in CI-Nutzern bis heute nicht existiert. Dabei ist es sehr
wahrscheinlich, dass gerade ImplantatstrÀger von einer entsprechenden Analyse
auf Hirnstammebene und höherrangigen Ebenen deutlich profitieren wĂŒrden, da
dies objektiv Anpassstrategien mit RĂŒcksicht auf eine bestmögliche binaurale
Integration ermöglichen könnte. Deshalb stellen wir ein weiteres, neuartiges
Verfahren zum Erhalt von neuralen Korrelaten binauraler Interaktion in bimodal
versorgten CI-TrĂ€gern vor, welches jĂŒngste Erfolge im Bereich der schnellen,
entfalltungsbasierten ABR Akquisition und der bereits vorgestellten Schmalband-
filterung zur Reduktion von Stimulationsartefakten kombiniert. Basierend auf
diesem Verfahren konnten signifikante Verbesserungen in der BIC-Amplitude in 10
bimodal versorgten Patienten sowie 10 normalhörenden Probanden, basierend auf
umgesetzte, interaurale Laufzeitkompensationen technischer Hörhilfen, aufgezeigt
werden.
Insgesamt demonstrieren beide vorgestellten Studien technisch-induzierte, interaurale
Laufzeitunterschiede und betonen demnach sehr deutlich potenzielle
Vorteile in assoziierten neuralen Korrelaten binauraler Interaktionen, wenn solche
MissverhÀltnisse zeitlich ausgeglichen werden. Die aufgezeigten Ergebnisse sowie
die getĂ€tigte AbschĂ€tzungen technischer Laufzeiten sollte in gröĂeren Gruppen
weiter untersucht werden, um die Aussagekraft weiter zu steigern. Dennoch
unterstreichen diese Einsichten das Verlangen nach binauralen LösungsansÀtzen
in der zukĂŒnftigen Hörrehabilitation, statt bisheriger isolierter und monauraler
Therapien
A comprehensive survey of wireless body area networks on PHY, MAC, and network layers solutions
Recent advances in microelectronics and integrated circuits, system-on-chip design, wireless communication and intelligent low-power sensors have allowed the realization of a Wireless Body Area Network (WBAN). A WBAN is a collection of low-power, miniaturized, invasive/non-invasive lightweight wireless sensor nodes that monitor the human body functions and the surrounding environment. In addition, it supports a number of innovative and interesting applications such as ubiquitous healthcare, entertainment, interactive gaming, and military applications. In this paper, the fundamental mechanisms of WBAN including architecture and topology, wireless implant communication, low-power Medium Access Control (MAC) and routing protocols are reviewed. A comprehensive study of the proposed technologies for WBAN at Physical (PHY), MAC, and Network layers is presented and many useful solutions are discussed for each layer. Finally, numerous WBAN applications are highlighted
A Three â tier bio-implantable sensor monitoring and communications platform
One major hindrance to the advent of novel bio-implantable sensor technologies is the need for a reliable power source and data communications platform capable of continuously, remotely, and wirelessly monitoring deeply implantable biomedical devices.
This research proposes the feasibility and potential of combining well established, âhuman-friendly' inductive and ultrasonic technologies to produce a proof-of-concept, generic, multi-tier power transfer and data communication platform suitable for low-power, periodically-activated implantable analogue bio-sensors.
In the inductive sub-system presented, 5 W of power is transferred across a 10 mm gap between a single pair of 39 mm (primary) and 33 mm (secondary) circular printed spiral coils (PSCs). These are printed using an 8000 dpi resolution photoplotter and fabricated on PCB by wet-etching, to the maximum permissible density.
Our ultrasonic sub-system, consisting of a single pair of Pz21 (transmitter) and Pz26 (receiver) piezoelectric PZT ceramic discs driven by low-frequency, radial/planar excitation (-31 mode), without acoustic matching layers, is also reported here for the first time. The discs are characterised by propagation tank test and directly driven by the inductively coupled power to deliver 29 ÎŒW to a receiver (implant) employing a low voltage start-up IC positioned 70 mm deep within a homogeneous liquid phantom. No batteries are used.
The deep implant is thus intermittently powered every 800 ms to charge a capacitor which enables its microcontroller, operating with a 500 kHz clock, to transmit a single nibble (4 bits) of digitized sensed data over a period of ~18 ms from deep within the phantom, to the outside world.
A power transfer efficiency of 83% using our prototype CMOS logic-gate IC driver is reported for the inductively coupled part of the system. Overall prototype system power consumption is 2.3 W with a total power transfer efficiency of 1% achieved across the tiers
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