ORCID Profile
0000-0003-3962-8965
Current Organisation
National Acoustics Laboratory
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Publisher: ACM
Date: 12-12-2010
Publisher: Springer Science and Business Media LLC
Date: 04-03-2015
Publisher: SPIE
Date: 07-06-2004
DOI: 10.1117/12.526483
Publisher: ASA
Date: 2013
DOI: 10.1121/1.4801054
Publisher: Acoustical Society of America (ASA)
Date: 11-1998
DOI: 10.1121/1.423886
Abstract: The head-related transfer function (HRTF) varies with range as well as with azimuth and elevation. To better understand its close-range behavior, a theoretical and experimental investigation of the HRTF for an ideal rigid sphere was performed. An algorithm was developed for computing the variation in sound pressure at the surface of the sphere as a function of direction and range to the sound source. The impulse response was also measured experimentally. The results may be summarized as follows. First, the experimental measurements were in close agreement with the theoretical solution. Second, the variation of low-frequency interaural level difference with range is significant for ranges smaller than about five times the sphere radius. Third, the impulse response reveals the source of the ripples observed in the magnitude response, and provides direct evidence that the interaural time difference is not a strong function of range. Fourth, the time delay is well approximated by well-known ray-tracing formula due to Woodworth and Schlosberg. Finally, except for this time delay, the HRTF for the ideal sphere appears to be minimum-phase, permitting exact recovery of the impulse response from the magnitude response in the frequency domain.
Publisher: IEEE Comput. Soc
Date: 2002
Publisher: ASA
Date: 2013
DOI: 10.1121/1.4800204
Publisher: ASA
Date: 2013
DOI: 10.1121/1.4800124
Publisher: Elsevier BV
Date: 04-2012
Publisher: SPIE
Date: 12-06-2003
DOI: 10.1117/12.473919
Publisher: Springer Science and Business Media LLC
Date: 11-1981
DOI: 10.3758/BF03202005
Publisher: SAGE Publications
Date: 15-04-2022
DOI: 10.1177/17479541211007611
Abstract: Elbow tendinopathy injuries are very common in tennis players. One of the commonly accepted theories describing the development of elbow tendinopathy in tennis is based on stiffness of the forearm skeletal muscle units and their repetitive overuse in the forehand stroke. Our objective was to use a novel microcontroller based wearable device to compare the influence of different forehand spin levels (flat, topspin and lob) and ball exit speed on forearm muscle activity in the potential onset of elbow tendinopathy in experienced adult tennis players. Peak normalised extensor carpi radialis (ECR) and flexor carpi radialis (FCR) muscle activity corresponding to each forehand shot and ball exit speed were determined and analysed. For the ECR shots (flat = 121, topspin = 272 and lob = 273) by 8 players, Kruskal-Wallis test (p 0.001) and Post-Hoc tests revealed a significant difference between the flat and topspin spin levels (p 0.01) and flat and lob spin levels (p 0.001). For the FCR shots (flat = 125, topspin = 301 and lob = 303) by 9 players, Kruskal-Wallis test showed no significant difference between the three spin levels. For the corresponding ball speed, the Kruskal-Wallis (p 0.001) and subsequent Post-Hoc (p 0.001) showed that flat hits had the significantly highest ball speed followed by topspin then lob accordingly for both muscles included shots. Our results suggest that coaches could consider recommending players to hit forehands with topspin in order to potentially reduce the risk of developing lateral elbow tendinopathy.
Publisher: Springer Science and Business Media LLC
Date: 07-1980
DOI: 10.3758/BF03206129
Abstract: Cardiac function is a major factor for tissue perfusion and therefore may affect the tissue oxygen saturation. Aim was to analyse possible associations between cardiac function parameters and cerebral and peripheral tissue oxygenation in neonates on the first day after birth. For the present study, we analysed secondary outcome parameters of a previously performed prospective single centre observational study. The prospective study was conducted at the Medical University of Graz, Austria between September 2011 and June 2013. We included preterm and term neonates who were admitted to the neonatal intensive care unit and in whom simultaneous near-infrared spectroscopy measurements and echocardiography were obtained on the first day after birth. Cardiac function parameters were correlated to cerebral and peripheral tissue oxygen saturation and cerebral and peripheral fractional tissue oxygen extraction at the time of echocardiography. A total of 60 neonates of whom 47 were preterm and 13 were term (median gestational age: 34 IQR 33-35 weeks, mean birth weight: 2276 ± 774 grams) were included. There were no statistically significant correlations between cardiac function parameters and regional tissue oxygenation parameters. In the present study, we found no correlation between regional tissue oxygenation and parameters of cardiac function in cardio-circulatory stable neonates on the first day after birth.
Publisher: Acoustical Society of America (ASA)
Date: 24-01-2006
DOI: 10.1121/1.2152294
Abstract: Equal sharpness contours for broadband noise were generated through matches made between a standard reference noise and comparison noise stimuli varying in spectral envelope. Based upon the results of the sharpness matching task, a set of 20 percussive broadband noise stimuli was constructed and presented to three subjects in a sharpness rating experiment using white noise as a standard stimulus. Predicting obtained sharpness ratings for these percussive broadband noise stimuli from first and second moments of the stimulus specific loudness distribution was more successful than conventional prediction based only upon the weighted first moment.
Publisher: WORLD SCIENTIFIC
Date: 03-2011
Publisher: IEEE Comput. Soc
Date: 2002
Publisher: IEEE
Date: 2005
Publisher: IEEE
Date: 05-2009
Publisher: Springer Science and Business Media LLC
Date: 30-08-2015
Publisher: Acoustical Society of America (ASA)
Date: 04-1980
DOI: 10.1121/1.384141
Abstract: Intelligibility of PB word lists embedded in simultaneous masking noise was evaluated before and after fatiguing-noise exposure. Intelligibility was determined by observing the number of words correctly repeated during a shadowing task. Both the speech signal and the masking noise were filtered to a 2825–3185-Hz band. Masking-noise levels were varied from 0- to 90-dB SL. Fatigue was produced by a 1500–3000-Hz octave band of noise at 115 dB (re 20 μPa) presented continuously for 5 min. The results of three experiments indicated that speech intelligibility was reduced when the speech was presented against a background of silence but that the fatiguing-noise exposure had no effect on intelligibility when the speech was made more intense and embedded in masking noise of 40–90-dB SL. These observations are interpreted by considering the recruitment produced by fatigue and masking noise.
Publisher: Acoustical Society of Japan
Date: 2001
DOI: 10.1250/AST.22.334
Publisher: WORLD SCIENTIFIC
Date: 03-2011
Publisher: Wiley
Date: 05-1981
DOI: 10.1113/JPHYSIOL.1981.SP013699
Abstract: 1. The ability of cats to detect sinusoidal grating patterns superimposed on one-dimensional visual noise was assessed using behavioural methods. 2. The magnitude of elevation in contrast threshold due to noise increased monotonically within limits with increasing noise contrast. 3. Visual noise was filtered using various techniques (band-reject, low-pass, high-pass and band-pass noise) filtered noise resulted in threshold elevation only when it contained frequencies similar to the test frequency. 4. In all cases the masking functions indicated that the band widths of the channels mediating detection ranged from +/- 0.50 to +/- 0.75 octaves across three spatial frequencies and that the channel sensitive to low spatial frequencies was asymmetrical in its tuning. 5. The spatial properties of these psychophysical detecting channels closely resemble the spatial frequency selectivity exhibited by some cat cortical neurones, both in the general narrowness of tuning and the asymmetry in tuning at lower, but not higher, spatial frequencies.
Publisher: ACM
Date: 27-07-2003
Publisher: Audio Engineering Society
Date: 22-05-2015
Publisher: ACM Press
Date: 1997
Publisher: Springer Science and Business Media LLC
Date: 05-1980
DOI: 10.3758/BF03204259
Abstract: Over recent years several ex les of randomly switching methyltransferases, associated with Type III restriction-modification (R-M) systems, have been described in pathogenic bacteria. In every case examined, changes in simple DNA sequence repeats result in variable methyltransferase expression and result in global changes in gene expression, and differentiation of the bacterial cell into distinct phenotypes. These epigenetic regulatory systems are called phasevarions, phase-variable regulons, and are widespread in bacteria, with 17.4% of Type III R-M system containing simple DNA sequence repeats. A distinct, recombination-driven random switching system has also been described in Streptococci in Type I R-M systems that also regulate gene expression. Here, we interrogate the most extensive and well-curated database of R-M systems, REBASE, by searching for all possible simple DNA sequence repeats in the hsdRMS genes that encode Type I R-M systems. We report that 7.9% of hsdS, 2% of hsdM, and of 4.3% of hsdR genes contain simple sequence repeats that are capable of mediating phase variation. Phase variation of both hsdM and hsdS genes will lead to differential methyltransferase expression or specificity, and thereby the potential to control phasevarions. These data suggest that in addition to well characterized phasevarions controlled by Type III mod genes, and the previously described Streptococcal Type I R-M systems that switch via recombination, approximately 10% of all Type I R-M systems surveyed herein have independently evolved the ability to randomly switch expression via simple DNA sequence repeats.
No related grants have been discovered for William Martens.