ORCID Profile
0000-0003-4636-753X
Current Organisation
University of Sydney
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Artificial Intelligence and Image Processing | Computer-Human Interaction | Sensory Processes, Perception And Performance | Simulation and Modelling | Virtual Reality And Related Simulation | Psychology | Computational Linguistics | Virtual Reality and Related Simulation | Communications Technologies Not Elsewhere Classified | Linguistic Processes (Incl. Speech Production And Comprehension) | Electrical and Electronic Engineering | Cognitive Science | Visual Arts And Crafts Not Elsewhere Classified | Linguistic Processes (incl. Speech Production and Comprehension) | Information Storage, Retrieval And Management | Sensory Systems | Integrated Circuits | Other Electronic Engineering | Computer Hardware | Motor Control | Fine Arts (Incl. Sculpture And Painting) | Processor Architectures | Computer Perception, Memory And Attention | Pattern Recognition and Data Mining | Signal Processing | Biological Mathematics | Text Processing | Film, Television and Digital Media | Other Cinema And Electronic Arts | Speech Recognition
Information processing services | Integrated systems | Behavioural and cognitive sciences | Expanding Knowledge in Engineering | Voice equipment | Hearing, vision, speech and their disorders | Communication equipment not elsewhere classified | Broadcasting | The creative arts | Combined operations | Broadcasting equipment | Information services not elsewhere classified | Hearing, Vision, Speech and Their Disorders | Expanding Knowledge in Language, Communication and Culture | Technological and Organisational Innovation | Computer equipment | Integrated circuits and devices | Communication services not elsewhere classified | Computer software and services not elsewhere classified | Expanding Knowledge in the Information and Computing Sciences |
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2022
Publisher: IOP Publishing
Date: 04-2010
Publisher: IEEE
Date: 10-2019
Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.COMPBIOMED.2012.09.004
Abstract: The conductivity distribution around the thorax is altered during the cardiac cycle due to the blood perfusion, heart contraction and lung inflation. Previous studies showed that these bio-impedance changes are appropriate for non-invasive cardiac function imaging using Electrical Impedance Tomography (EIT) techniques. However, the spatial resolution is presently low. One of the main obstacles in cardiac imaging at the heart location is the large impedance variation of the lungs by respiration and muscles on the dorsal and posterior side of the body. In critical care units there is a potential to insert an internal electrode inside the esophagus directly behind the heart in the same plane of the external electrodes. The aim of the present study is to evaluate different current stimulation and measurement patterns with both external and internal electrodes. Analysis is performed with planar arrangement of 16 electrodes for a simulated 3D cylindrical tank and pig thorax model. In our study we evaluated current injection patterns consisting of adjacent, diagonal, trigonometric, and radial to the internal electrode. The performance of these arrangements was assessed using quantitative methods based on distinguishability, sensitivity and GREIT (Graz consensus Reconstruction algorithm for Electrical Impedance Tomography). Our evaluation shows that an internal electrode configuration based on the trigonometric injection patterns has better performance and improves pixel intensity of the small conductivity changes related to heart near 1.7 times in reconstructed images and also shows more stability with different levels of added noise. For the internal electrode, when we combined radial or adjacent injection with trigonometric injection pattern, we found an improvement in litude response. However, the combination of diagonal with trigonometric injection pattern deteriorated the shape deformation (correlation coefficient r=0.344) more than combination of radial and trigonometric injection (correlation coefficient r=0.836) for the perturbations in the area close to the center of the cylinder. We also find that trigonometric stimulation pattern performance is degraded in a realistic thorax model with anatomical asymmetry. For that reason we recommend using internal electrodes only for voltage measurements and as a reference electrode during trigonometric stimulation patterns in practical measurements.
Publisher: IEEE
Date: 10-2011
Publisher: IEEE
Date: 03-2012
Publisher: Frontiers Media SA
Date: 22-11-2019
Publisher: IEEE
Date: 04-2009
Publisher: Association for Computing Machinery (ACM)
Date: 15-12-2017
DOI: 10.1145/3106744
Abstract: Kernel adaptive filters (KAFs) are online machine learning algorithms which are amenable to highly efficient streaming implementations. They require only a single pass through the data and can act as universal approximators, i.e. approximate any continuous function with arbitrary accuracy. KAFs are members of a family of kernel methods which apply an implicit non-linear mapping of input data to a high dimensional feature space, permitting learning algorithms to be expressed entirely as inner products. Such an approach avoids explicit projection into the feature space, enabling computational efficiency. In this paper, we propose the first fully pipelined implementation of the kernel normalised least mean squares algorithm for regression. Independent training tasks necessary for hyperparameter optimisation fill pipeline stages, so no stall cycles to resolve dependencies are required. Together with other optimisations to reduce resource utilisation and latency, our core achieves 161 GFLOPS on a Virtex 7 XC7VX485T FPGA for a floating point implementation and 211 GOPS for fixed point. Our PCI Express based floating-point system implementation achieves 80% of the core’s speed, this being a speedup of 10× over an optimised implementation on a desktop processor and 2.66× over a GPU.
Publisher: IEEE
Date: 10-2016
Publisher: IEEE
Date: 03-2016
Publisher: IEEE
Date: 09-2018
Publisher: IEEE
Date: 07-2014
Publisher: MIT Press
Date: 2018
DOI: 10.1162/COMJ_A_00439
Abstract: We present and discuss the Agent Designer, a system that enables users of digital audio workstations to generate novel high-level structures for their compositions based on previous ex les. The system uses variable-order Markov models and rule induction to learn both temporal relations and structural relations between parts in a piece of music. As is usual in machine learning, however, the quality of the learning can be improved greatly by users specifying relevant features. The Agent Designer therefore points to important design and human–computer interaction problems, as well as algorithmic challenges. We present a number of studies that help to understand how effective the Agent Designer is and how we might design a user interface that best enables users to obtain quality results from the system. We show that the Agent Designer is effective for certain musical styles, such as loop-based electronic music, and that we as expert users can design agents that produce the most effective results. We also note that it remains a challenge to automate this process fully.
Publisher: IEEE
Date: 03-2017
Publisher: IEEE
Date: 2006
Publisher: IEEE
Date: 2006
Publisher: Informa UK Limited
Date: 12-2009
Publisher: IOP Publishing
Date: 14-08-2013
DOI: 10.1088/0967-3334/34/9/991
Abstract: We present an innovative bio-potential front-end capable of recording true unipolar ECG leads for the first time without making use of the Wilson central terminal. In addition to the convenience in applications such as continuous monitoring and rapid diagnosis, the information in unipolar recordings may yield unique diagnostic information as it avoids the need to essentially subtract data or make use of the averaging effect imposed from the Wilson central terminal. The system also allows direct, real-time software calculation of signals corresponding to standard ECG leads which achieve correlations in excess of 92% with a gold standard ECG during a parallel in vivo recording. In addition, the implemented circuit is wideband (0.05-1000 Hz), compatible with standard (Ag/AgCl) bio-potential electrodes, and dry (paste-less) textile electrodes. The circuit is also low power, requiring less than 50 mW (when powered at 12 V) per standard ECG lead (two channels required). It is therefore well suited for wearable, long-term applications.
Publisher: Acoustical Society of America (ASA)
Date: 12-2019
DOI: 10.1121/1.5138594
Abstract: When a broadband source of radiated noise transits past a fixed hydrophone, a Lloyd's mirror constructive/destructive interference pattern can be observed in the output spectrogram. By taking the spectrum of a (log) spectrum, the power cepstrum detects the periodic structure of the Lloyd's mirror fringe pattern by generating a sequence of pulses located at the fundamental quefrency and its multiples. The fundamental quefrency, which is the reciprocal of the frequency difference between adjacent destructive interference fringes, equates to the multipath delay time. An experiment is conducted where a motorboat transits past a hydrophone located about 1 m above the seafloor in very shallow water (20 m deep). The hydrophone has a frequency bandwidth of 90 kHz, and its output is s led at 250 kHz. A cepstrogram database is compiled from multiple vessel transits, and its cepstrum-based feature vectors (along with ground-truth range data) form the input to train a convolutional neural network (CNN) so that it can predict the source range relative to the hydrophone for other (“unseen”) vessel transits. The CNN provides an accurate prediction of the instantaneous source range even when the range estimate from conventional multipath passive ranging is biased, which occurs at low grazing angles (& °).
Publisher: IEEE
Date: 05-2010
Publisher: IEEE
Date: 04-2009
Publisher: IEEE
Date: 04-2018
Publisher: CRC Press
Date: 19-12-2011
DOI: 10.1201/B11205-8
Publisher: Elsevier BV
Date: 02-2017
Publisher: WORLD SCIENTIFIC
Date: 03-2011
Publisher: American Physiological Society
Date: 11-2004
Abstract: Virtual auditory space (VAS) stimuli based on outer ear transfer functions became increasingly important in spatial hearing research. However, few studies have investigated the match between responses of auditory neurons to VAS and free-field (FF) stimulation. This study validates acoustic spatial receptive fields (SRFs) of 183 in idual midbrain units using both VAS and FF stimuli. The first-spike latency, which varied systematically across SRFs, was 14.9 ± 8.3 (SD) ms in FF, and 15.1 ± 8.3 ms in VAS. Spike-count-based SRFs measured 0–20 dB above the neural threshold covered on average 44.5 ± 18.0% of the recorded sphere in FF and 45.5 ± 18.7% in VAS. The average deviation of the centroid position of SRFs using FF and VAS stimuli was 7.4° azimuth and 3.3° elevation. The average spike rate remained unchanged. The SRF overlap recorded using FF and VAS stimuli (mean: 71.3 ± 12.6%) or repeated FF stimuli (70.2 ± 14.2%) was high and strongly correlated ( r = 0.96 P 0.05). The SRF match observed with FF and VAS stimuli was not significantly altered over a range of stimulus levels (paired t-test P = 0.51 n = 6). Randomized VAS barely affected SRF sizes, centroids, or maximum spike count but decreased the average minimum response to 59% compared with sequential stimulation (paired t-test P = 0.05 n = 26). SRF recordings in VAS excluding the acoustic distortions of the recording equipment differed from those in VAS incorporating the equipment (paired t-test P = 0.01 n = 5). In conclusion, neurophysiological recordings demonstrate that in idualized VAS stimuli provided a good simulation of a FF environment.
Publisher: IEEE
Date: 05-2010
Publisher: WORLD SCIENTIFIC
Date: 03-2011
Publisher: IEEE
Date: 08-2012
Publisher: IEEE
Date: 1998
Publisher: Association for Computing Machinery (ACM)
Date: 22-06-2023
DOI: 10.1145/3567429
Abstract: The spectral correlation density (SCD) is an important tool in cyclostationary signal detection and classification. Even using efficient techniques based on the fast Fourier transform (FFT), real-time implementations are challenging because of the high computational complexity. A key dimension for computational optimization lies in minimizing the wordlength employed. In this article, we analyze the relationship between wordlength and signal-to-quantization noise in fixed-point implementations of the SCD function. A canonical SCD estimation algorithm, the FFT accumulation method (FAM) using fixed-point arithmetic, is studied. We derive closed-form expressions for SQNR and compare them at wordlengths ranging from 14 to 26 bits. The differences between the calculated SQNR and bit-exact simulations are less than 1 dB. Furthermore, an HLS-based FPGA design is implemented on a Xilinx Zynq UltraScale+ XCZU28DR-2FFVG1517E RFSoC. Using less than 25% of the logic fabric on the device, it consumes 7.7 W total on-chip power and has a power efficiency of 12.4 GOPS/W, which is an order of magnitude improvement over an Nvidia Tesla K40 graphics processing unit (GPU) implementation. In terms of throughput, it achieves 50 MS/sec, which is a speedup of 1.6 over a recent optimized FPGA implementation.
Publisher: IEEE
Date: 05-2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2016
Publisher: IEEE
Date: 10-2011
Publisher: IEEE
Date: 2003
Publisher: Springer Science and Business Media LLC
Date: 08-11-2016
DOI: 10.1038/SREP36052
Abstract: Under-nutrition in neonates can cause immediate mortality, impaired cognitive development and early onset adult disease. Body fat percentage measured using air-displacement-plethysmography has been found to better indicate under-nutrition than conventional birth weight percentiles. However, air-displacement-plethysmography equipment is expensive and non-portable, so is not suited for use in developing communities where the burden is often the greatest. We proposed a new body fat measurement technique using a length-free model with near-infrared spectroscopy measurements on a single site of the body - the thigh. To remove the need for length measurement, we developed a model with five discrete wavelengths and a sex parameter. The model was developed using air-displacement-plethysmography measurements in 52 neonates within 48 hours of birth. We identified instrumentation required in a low-cost LED-based screening device and incorporated a receptor device that can increase the amount of light collected. This near-infrared method may be suitable as a low cost screening tool for detecting body fat levels and monitoring nutritional interventions for malnutrition in neonates and young children in resource-constrained communities.
Publisher: ACM
Date: 28-11-2011
Publisher: IEEE
Date: 08-2010
Publisher: IEEE
Date: 05-2008
Publisher: SAGE Publications
Date: 09-2007
DOI: 10.1260/174795407782233083
Abstract: The identification of elite swimmers' race patterns at the same time is an important unresolved problem. This problem appears to be of fundamental importance for coaches in training promising elite swimmers. To address this problem, a system of cluster analysis for studying group structures on the basis of elite swimmers' race results and various available race components, such as lengths, speeds and times, is described that uses standard statistical algorithms to arrange elite swimmers according to similarity in their race patterns. The outputs are displayed graphically using tree-like dendrograms, conveying elite swimmers' race patterns in a form intuitive for coaches. As an illustration of this, we have used this method to uncover a number of key race components in connection with Ian Thorpe's race results in the men's 400m freestyle final at the Sydney 2000 Summer Olympics
Publisher: Acoustical Society of Japan
Date: 2020
DOI: 10.1250/AST.41.16
Publisher: MDPI AG
Date: 13-02-2019
DOI: 10.3390/S19040772
Abstract: The Open-electroencephalography (EEG) framework is a popular platform to enable EEG measurements and general purposes Brain Computer Interface experimentations. However, the current platform is limited by the number of available channels and electrode compatibility. In this paper we present a fully configurable platform with up to 32 EEG channels and compatibility with virtually any kind of passive electrodes including textile, rubber and contactless electrodes. Together with the full hardware details, results and performance on a single volunteer participant (limited to alpha wave elicitation), we present the brain computer interface (BCI)2000 EEG source driver together with source code as well as the compiled (.exe). In addition, all the necessary device firmware, gerbers and bill of materials for the full reproducibility of the presented hardware is included. Furthermore, the end user can vary the dry-electrode reference circuitry, circuit bandwidth as well as s le rate to adapt the device to other generalized biopotential measurements. Although, not implemented in the tested prototype, the Biomedical Analogue to Digital Converter BIOADC naturally supports SPI communication for an additional 32 channels including the gain controller. In the appendix we describe the necessary modification to the presented hardware to enable this function.
Publisher: ACM Press
Date: 2006
Publisher: World Scientific Pub Co Pte Lt
Date: 10-1999
DOI: 10.1142/S0129065799000459
Abstract: In this work we study the influence and relationship of five different acoustical cues to the human sound localisation process. These cues are: interaural time delay, interaural level difference, interaural spectrum, monaural spectrum, and band-edge spectral contrast. Of particular interest was the synthesis and integration of the different cues to produce a coherent and robust percept of spatial location. The relative weighting and role of the different cues was investigated using band-pass filtered white noise with a frequency range (in kHz) of: 0.3–5, 0.3–7, 0.3–10, 0.3–14, 3–8, 4–9, and 7-14. These stimuli provided varying amounts of spectral information and physiologically detectable temporal information, thus probing the localisation process under varying sound conditions. Three subjects with normal hearing in both ears have performed five trials of 76 test positions for each of these stimuli in an anechoic room. All subjects showed systematic mislocalisation on most of these stimuli. The location to which they are mislocalised varies among subjects but in a systematic manner related to the five different acoustical cues. These cues have been correlated with the subject's localisation responses on an in idual basis with the results suggesting that the internal weighting of the spectral cues may vary with the sound condition.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2014
Publisher: Informa UK Limited
Date: 2009
DOI: 10.3109/14992020903079332
Abstract: To study the spatial hearing abilities of bilateral hearing-aid users in multi-talker situations, 20 subjects received fittings configured to preserve acoustic cues salient for spatial hearing. Following acclimatization, speech reception thresholds (SRTs) were measured for three competing talkers that were either co-located or spatially separated along the front-back or left-right dimension. In addition, the subjects' working memory and attentional abilities were measured. Left-right SRTs varied over more than 14 dB, while front-back SRTs varied over more than 8 dB. Furthermore, significant correlations were observed between left-right SRTs, age, and low-frequency hearing loss, and also between front-back SRTs, age, and high-frequency aided thresholds. Concerning cognitive effects, left-right performance was most strongly related to attentional abilities, while front-back performance showed a relation to working memory abilities. Altogether, these results suggest that, due to raised hearing thresholds and aging, hearing-aid users have reduced access to interaural and monaural spatial cues as well as a diminished ability to 'enhance' a target signal by means of top-down processing. These deficits, in turn, lead to impaired functioning in complex listening environments.
Publisher: IEEE
Date: 05-2013
Publisher: IEEE
Date: 05-2013
Publisher: Acoustical Society of Japan
Date: 2020
DOI: 10.1250/AST.41.308
Publisher: IEEE
Date: 11-2200
Publisher: IEEE
Date: 11-2007
Publisher: Wiley
Date: 13-10-2017
Publisher: InTech
Date: 08-01-2011
DOI: 10.5772/13554
Publisher: WORLD SCIENTIFIC
Date: 03-2011
Publisher: SAGE Publications
Date: 2012
DOI: 10.1255/JNIRS.975
Abstract: Optical coherence tomography (OCT) is a technique that is able to provide cross section views of tissue layers. This fast and non-invasive method is widely used in clinical applications for the diagnosis and treatment of certain diseases. Although conventional OCT is derived from the theory of interferometric imaging, emerging developments, including spectroscopic OCT and related techniques such as dual-band OCT and Raman spectroscopy–OCT, have resulted in significantly improved clinical capabilities for observing the tissue layers through enhanced tissue definition, image resolution, image contrast and scanning speed. This paper reviews the state-of-the-art developments of OCT. It starts with a general introduction of conventional interferometric OCT imaging methods including the time-domain and frequency-domain techniques. The second section explores the advances introduced from spectroscopy techniques in OCT, especially with spectroscopic OCT, dual-band OCT and Raman spectroscopy combined OCT. The final section discusses the current challenges in the application of approaches based on computer-aided diagnosis (CAD) for retinal imaging, for ex le automated segmentation of tissue layers and tracking disease progression. This task is currently limited by the quality of the recorded data from OCT systems but will be improved by adopting spectroscopic techniques. Finally, we analyse and discuss the improvements that are expected in retinal CAD from the adoption of newly emerging near infrared spectroscopy OCT at multiple wavelengths.
Publisher: Public Library of Science (PLoS)
Date: 25-10-2023
Publisher: IOP Publishing
Date: 26-05-2015
DOI: 10.1088/0967-3334/36/6/1297
Abstract: Recent studies showed that regional pulmonary perfusion can be reliably estimated using electrical impedance tomography (EIT) with the aid of hypertonic saline based contrast enhancement. Building on these successful studies, we studied contrast EIT for pulmonary perfusion defect caused by an artificially induced pulmonary embolism (PE) in a large ovine model (N = 8, 78 ± 7.8 kg). Furthermore, the efficacy of a less invasive contrast bolus of 0.77 ml kg(-1) of NaCl 3% was compared with a more concentrated bolus of 0.13 ml kg(-1) of NaCl 20%. Prior to the injection of each contrast bolus injection, ventilation was turned off to provide a total of 40 to 45 s of apnoea. Each bolus of impedance contrast was injected through a catheter into the right atrium. Pulmonary embolisation was performed by balloon occlusion of part of the right branch of the pulmonary trunk. Four parameters representing the kinetics of the contrast dilution in the lung were evaluated for statistical differences between baseline and PE, including peak value, maximum uptake, maximum washout and area under the curve of the averaged contrast dilution curve in each lung. Furthermore, the right lung to left lung (R2L) ratio of each the aforementioned parameters were assessed. While all of the R2L ratios yielded significantly different means between baseline and PE, it can be concluded that the R2L ratios of area under the curve and peak value of the averaged contrast dilution curve are the most promising and reliable in assessing PE. It was also found that the efficacy of the two types of impedance contrasts were not significantly different in distinguishing PE from baseline in our model.
Publisher: IEEE
Date: 12-2011
Publisher: IEEE
Date: 04-2015
Publisher: Oxford University Press (OUP)
Date: 2009
DOI: 10.1080/13693780802510232
Abstract: Aspergillus spp. are leading causes of morbidity and mortality in immunocompromised patients. This review provides an overview of host defenses, the mechanisms by which the alveolar-capillary barrier is breeched by Aspergillus, and the implications for diagnosis and treatment of patients with invasive pulmonary aspergillosis.
Publisher: Springer Science and Business Media LLC
Date: 18-01-2021
Publisher: Frontiers Media SA
Date: 2010
Publisher: IEEE
Date: 12-2017
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.CLINPH.2009.12.025
Abstract: We present a new, low power EEG recording system with an ultra-high input impedance that enables the use of long-lasting, passive dry electrodes. It incorporates Bluetooth wireless connectivity and is designed to be suitable for long-term monitoring during daily activities. The new EEG system is compared to a standard and clinically available reference EEG system using wet electrodes in three separate sets of experiments. In the first two experiments, each dry electrode was surrounded by four standard wet electrodes and the alpha and mu-rhythms were recorded. In the third experiment, serial monopolar (referred to the left ear) recordings of flash visual evoked potential were performed using the new EEG system and a reference system. These experiments showed that the signal recorded using the new EEG system is almost identical to that recorded with standard clinical EEG equipment our measurements showed that the correlation coefficient between the dry electrode recordings and the average of the four standard electrodes surrounding each dry electrode is greater than 0.85. We conclude that the new EEG system performs similarly to reference EEG systems, while providing the advantages of portability, ease of application and minimal scalp preparation. The proposed system using passive dry electrodes suitable for single use while performing as good as standard EEG equipment provides ease of application and minimal scalp preparation.
Publisher: IEEE
Date: 05-2008
Publisher: IEEE
Date: 08-2014
Publisher: IEEE
Date: 05-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2017
Publisher: IEEE
Date: 05-2019
Publisher: IEEE
Date: 12-2008
Publisher: IEEE
Date: 05-2013
Publisher: IOP Publishing
Date: 04-2010
Publisher: IEEE
Date: 04-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2007
Publisher: IEEE
Date: 12-2010
Publisher: IOP Publishing
Date: 24-04-2012
DOI: 10.1088/0967-3334/33/5/817
Abstract: Electrode contact impedance is a crucial factor in physiological measurements and can be an accuracy-limiting factor when performing electroencephalography and electrical impedance tomography. In this work, standard flat electrodes and micromachined multipoint spiked electrodes are characterized with a finite-element method electromagnetic solver and the dependence of the contact impedance on geometrical factors is explored. It is found that flat electrodes are sensitive to changes in the outer skin layer properties related to hydration and thickness, while spike electrodes are not. The impedance as a function of the effective contact area, number of spikes and penetration depth has also been studied and characterized.
Publisher: IEEE
Date: 07-2008
Publisher: Springer Science and Business Media LLC
Date: 2012
Publisher: Frontiers Media SA
Date: 2012
Publisher: Acoustical Society of America (ASA)
Date: 12-2011
DOI: 10.1121/1.3658443
Abstract: The design and construction of a circular microphone array (CMA) that has a wide frequency range suitable for human hearing is presented. The design of the CMA was achieved using a technique based on simulated directivity index (DI) curves. The simulated DI curves encapsulate the critical microphone array performance limitations: spatial aliasing, measurement noise, and microphone placement errors. This paper demonstrates how the non-regularized DI curves for a given beamforming order clearly define the bandwidth of operation, in other words, the frequency band for which the beamformer has relatively constant and maximum directivity. Detailed and comprehensive experimental data that characterizes the CMA beamformer are also presented.
Publisher: IEEE
Date: 05-2011
Publisher: IEEE
Date: 03-2017
Publisher: IEEE
Date: 07-2008
Publisher: Acoustical Society of America (ASA)
Date: 04-2009
DOI: 10.1121/1.3081395
Abstract: A method for synthesizing near-field head-related transfer functions (HRTFs) from far-field HRTFs measured using an acoustic point-source of sound is presented. Near-field HRTFs are synthesized by applying an analytic function describing the change in the transfer function when the location of a sound source changes from the far-field to the near-field: the distance variation function (DVF). The DVF is calculated from a rigid sphere model and approximates the change in the frequency-dependent interaural level cues as a function of the change in sound source distance. Using a sound localization experiment, the fidelity of the near-field virtual auditory space (VAS) generated using this technique is compared to that obtained by simply adjusting the intensity of the VAS stimulus to simulate changes in distance. Results show improved distance perception for sounds at simulated distances of up to 60cm using the DVF compared to simple intensity adjustment, while maintaining directional accuracy. The largest improvement for distance perception were for sound sources located to the side and within 40cm. When intensity was removed as a cue for sound source distance from near-field sounds generated using the DVF, results showed some discrimination of sound source distances but, in general, distance perception accuracy was poor.
Publisher: Springer Science and Business Media LLC
Date: 18-06-2003
Publisher: Informa UK Limited
Date: 09-2012
DOI: 10.2147/MDER.S36691
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2011
Publisher: IEEE
Date: 07-2014
DOI: 10.1109/ICME.2012.93
Publisher: IEEE
Date: 05-2014
Publisher: InTech
Date: 2010
DOI: 10.5772/7027
Publisher: Elsevier BV
Date: 02-2017
Publisher: IEEE
Date: 2003
Publisher: IEEE
Date: 08-2010
Publisher: IEEE
Date: 2006
Publisher: Acoustical Society of America (ASA)
Date: 07-2005
DOI: 10.1121/1.1926107
Abstract: This study measured the accuracy with which human listeners can localize spoken words. A broadband (300Hz–16kHz) corpus of monosyllabic words was created and presented to listeners using a virtual auditory environment. Localization was examined for 76 locations on a sphere surrounding the listener. Experiment 1 showed that low-pass filtering the speech sounds at 8kHz degraded performance, causing an increase in polar angle errors associated with the cone of confusion. In experiment 2 it was found that performance in fact varied systematically with the level of the signal above 8kHz. Although the lower frequencies (below 8kHz) are known to be sufficient for accurate speech recognition in most situations, these results demonstrate that natural speech contains information between 8 and 16kHz that is essential for accurate localization.
Publisher: Wiley
Date: 13-10-2017
Publisher: Informa UK Limited
Date: 07-2010
DOI: 10.2147/MDER.S9321
Publisher: MIT Press - Journals
Date: 06-2009
DOI: 10.1162/NECO.2009.06-07-548
Abstract: We present a first-order nonhomogeneous Markov model for the interspike-interval density of a continuously stimulated spiking neuron. The model allows the conditional interspike-interval density and the stationary interspike-interval density to be expressed as products of two separate functions, one of which describes only the neuron characteristics and the other of which describes only the signal characteristics. The approximation shows particularly clearly that signal autocorrelations and cross-correlations arise as natural features of the interspike-interval density and are particularly clear for small signals and moderate noise. We show that this model simplifies the design of spiking neuron cross-correlation systems and describe a four-neuron mutual inhibition network that generates a cross-correlation output for two input signals.
Publisher: American Association of Physics Teachers (AAPT)
Date: 06-1987
DOI: 10.1119/1.15120
Abstract: A table-top demonstration model which simulates the orientational ordering of diatomic molecules on two-dimensional lattices is described. Fundamental ideas and phenomena concerning collective excitations (libron waves) and the effects of disorder on frustrated systems are illustrated by means of simple demonstrations.
Publisher: IEEE
Date: 1998
Publisher: IEEE
Date: 07-2008
Publisher: Elsevier BV
Date: 03-2012
Publisher: Wissenschaftliche Verlagsgesellschaft mbH
Date: 09-2014
DOI: 10.3813/AAA.918772
Publisher: IEEE
Date: 04-2017
Publisher: Institution of Engineering and Technology (IET)
Date: 1999
DOI: 10.1049/EL:19990998
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2014
Publisher: Springer US
Date: 2010
Publisher: Wissenschaftliche Verlagsgesellschaft mbH
Date: 2012
DOI: 10.3813/AAA.918495
Publisher: Springer Berlin Heidelberg
Date: 2013
Publisher: IOP Publishing
Date: 24-04-2012
DOI: 10.1088/0967-3334/33/5/695
Abstract: Although electrical impedance tomography (EIT) for ventilation monitoring is on the verge of clinical trials, pulmonary perfusion imaging with EIT remains a challenge, especially in spontaneously breathing subjects. In anticipation of more research on this subject, we believe a thorough review is called for. In this paper, findings related to the physiological origins and electrical characteristics of this signal are summarized, highlighting properties that are particularly relevant to EIT. The perfusion impedance change signal is significantly smaller in litude compared with the changes due to ventilation. Therefore, the hardware used for this purpose must be more sensitive and more resilient to noise. In previous works, some signal- or image-processing methods have been required to separate these two signals. Three different techniques are reviewed in this paper, including the ECG-gating method, frequency-domain-filtering-based methods and a principal-component-analysis-based method. In addition, we review a number of experimental studies on both human and animal subjects that employed EIT for perfusion imaging, with promising results in the diagnosis of pulmonary embolism (PE) and pulmonary arterial hypertension as well as other potential applications. In our opinion, PE is most likely to become the main focus for perfusion EIT in the future, especially for heavily instrumented patients in the intensive care unit (ICU).
Publisher: Institution of Engineering and Technology (IET)
Date: 2012
DOI: 10.1049/EL.2011.3651
Publisher: IEEE
Date: 05-2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2017
Publisher: Springer US
Date: 2010
Publisher: IEEE
Date: 09-2015
Publisher: IEEE
Date: 10-2017
Publisher: Australian Mathematical Publishing Association, Inc.
Date: 17-06-2010
Publisher: IEEE
Date: 03-2012
Publisher: Springer Science and Business Media LLC
Date: 26-02-2014
DOI: 10.1007/S00422-014-0588-4
Abstract: In recent years, a great deal of research within the field of sound localization has been aimed at finding the acoustic cues that human listeners use to localize sounds and understanding the mechanisms by which they process these cues. In this paper, we propose a complementary approach by constructing an ideal-observer model, by which we mean a model that performs optimal information processing within a Bayesian context. The model considers all available spatial information contained within the acoustic signals encoded by each ear. Parameters for the optimal Bayesian model are determined based on psychoacoustic discrimination experiments on interaural time difference and sound intensity. Without regard as to how the human auditory system actually processes information, we examine the best possible localization performance that could be achieved based only on analysis of the input information, given the constraints of the normal auditory system. We show that the model performance is generally in good agreement with the actual human localization performance, as assessed in a meta-analysis of many localization experiments (Best et al. in Principles and applications of spatial hearing, pp 14-23. World Scientific Publishing, Singapore, 2011). We believe this approach can shed new light on the optimality (or otherwise) of human sound localization, especially with regard to the level of uncertainty in the input information. Moreover, the proposed model allows one to study the relative importance of various (combinations of) acoustic cues for spatial localization and enables a prediction of which cues are most informative and therefore likely to be used by humans in various circumstances.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2008
Publisher: IEEE
Date: 11-2008
Publisher: Hindawi Limited
Date: 2012
DOI: 10.1155/2012/585786
Abstract: There is a need in critical care units for continuous cardiopulmonary monitoring techniques. ECG gated electrical impedance tomography is able to localize the impedance variations occurring during the cardiac cycle. This method is a safe, inexpensive and potentially fast technique for cardiac output imaging but the spatial resolution is presently low, particularly for central locations such as the heart. Many parameters including noise deteriorate the reconstruction result. One of the main obstacles in cardiac imaging at the heart location is the high impedance of lungs and muscles on the dorsal and posterior side of body. In this study we are investigating improvements of the measurement and initial conductivity estimation of the internal electrode by modelling an internal electrode inside the esophagus. We consider 16 electrodes connected around a cylindrical mesh. With the random noise level set near 0.05% of the signal we evaluated the Graz consensus reconstruction algorithm for electrical impedance tomography. The modelling and simulation results showed that the quality of the target in reconstructed images was improved by up to 5 times for litude response, position error, resolution, shape deformation and ringing effects with perturbations located in cardiac related positions when using an internal electrode.
Publisher: IEEE
Date: 12-2014
Publisher: IEEE
Date: 05-2011
Publisher: InTech
Date: 23-08-2011
DOI: 10.5772/25282
Publisher: IEEE
Date: 2008
Publisher: IEEE
Date: 1999
Publisher: Acoustical Society of America (ASA)
Date: 06-2004
DOI: 10.1121/1.1736649
Abstract: A human psychoacoustical experiment is described that investigates the role of the monaural and interaural spectral cues in human sound localization. In particular, it focuses on the relative contribution of the monaural versus the interaural spectral cues towards resolving directions within a cone of confusion (i.e., directions with similar interaural time and level difference cues) in the auditory localization process. Broadband stimuli were presented in virtual space from 76 roughly equidistant locations around the listener. In the experimental conditions, a “false” flat spectrum was presented at the left eardrum. The sound spectrum at the right eardrum was then adjusted so that either the true right monaural spectrum or the true interaural spectrum was preserved. In both cases, the overall interaural time difference and overall interaural level difference were maintained at their natural values. With these virtual sound stimuli, the sound localization performance of four human subjects was examined. The localization performance results indicate that neither the preserved interaural spectral difference cue nor the preserved right monaural spectral cue was sufficient to maintain accurate elevation judgments in the presence of a flat monaural spectrum at the left eardrum. An explanation for the localization results is given in terms of the relative spectral information available for resolving directions within a cone of confusion.
Publisher: Acoustical Society of America (ASA)
Date: 09-2000
DOI: 10.1121/1.1288411
Abstract: This paper examines the role of biological constraints in the human auditory localization process. A psychophysical and neural system modeling approach was undertaken in which performance comparisons between competing models and a human subject explore the relevant biologically plausible “realism constraints.” The directional acoustical cues, upon which sound localization is based, were derived from the human subject’s head-related transfer functions (HRTFs). Sound stimuli were generated by convolving bandpass noise with the HRTFs and were presented to both the subject and the model. The input stimuli to the model were processed using the Auditory Image Model of cochlear processing. The cochlear data were then analyzed by a time-delay neural network which integrated temporal and spectral information to determine the spatial location of the sound source. The combined cochlear model and neural network provided a system model of the sound localization process. Aspects of humanlike localization performance were qualitatively achieved for broadband and bandpass stimuli when the model architecture incorporated frequency ision (i.e., the progressive integration of information across the different frequency channels) and was trained using variable bandwidth and center-frequency sounds. Results indicate that both issues are relevant to human sound localization performance.
Start Date: 2013
End Date: 2016
Funder: Australian Research Council
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Funder: Australian Research Council
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Funder: Australian Research Council
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End Date: 12-2010
Amount: $519,265.00
Funder: Australian Research Council
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End Date: 07-2007
Amount: $200,000.00
Funder: Australian Research Council
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Funder: Australian Research Council
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Amount: $25,000.00
Funder: Australian Research Council
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Amount: $289,437.00
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Amount: $277,000.00
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Amount: $330,000.00
Funder: Australian Research Council
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Amount: $20,000.00
Funder: Australian Research Council
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Amount: $10,000.00
Funder: Australian Research Council
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Amount: $200,000.00
Funder: Australian Research Council
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Amount: $2,000,000.00
Funder: Australian Research Council
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Amount: $20,000.00
Funder: Australian Research Council
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