bluuebunny/crossref_metadata_2025 huggingface dataset:
Seafloor sound-speed profile and interface dip angle measurement by the image source method: Application to real data
Authors: Pinson Samuel , Holland Charles W.
Published: October 2014

The image source method characterizes the sediment sound-speed profile from seafloor reflection data with a low computational cost compared with inversion techniques. Recently, the method has been extended to treat non-parallel sediment layering. The method is applied to data from an autonomous underwater vehicle (AUV) towing a source (1600–3500 Hz) and an horizontal array of hydrophones. AUV reflection measurements were acquired every 3 m along 10 criss-cross lines over a 1km<+>2<+> area with evidently dipping layers. Mapping the along track sound-speed profiles in geographical coordinates results in a pseudo-3D (Nx2D) sediment structure characterization of the area down to several tens of meters in the sub-bottom. The sound speed profile agreement at crossing points is quite good.
Requirements, technology, and science drivers of applied reverberation modeling
Authors: Eller Anthony I. , Heaney Kevin D.
Published: October 2014

The historical development of reverberation modeling is a story driven by both supporting and sometimes conflicting features of application requirements, measurement and computing capability, and scientific understanding. This paper presents an overview of how underwater reverberation modeling technology has responded to application needs and how this process has helped the community to identify and resolve related science issues. Emphasis is on the areas of System Design and Acquisition Support, Deployment and Operational Support, and Training Support. Gaps in our scientific knowledge are identified and recent advances are described that help push forward our collective understanding of how to predict and mitigate reverberation.
Physics of backscattering in terms of mode coupling applied to measured seabed roughness spectra in shallow water
Authors: Knobles David P.
Published: October 2014

Energy conserving coupled integral equations for the forward and backward propagating modal components have been previously developed [J. Acoust. Soc. Am. 130, 2673–2680 (2011)]. A rough seabed surface leads to a backscattered field and modifies the interference structure of the forward propagating field. Perturbation theory applied to the basic coupled integral equations allows for physical insight into the correlation of the roughness spectrum to the forward and backward modal intensities and cross mode coherence. This study applies the Nx2D integral equation coupled-mode approach to 3-D roughness measurements and examines the physics of the coupling of the forward and backward field components and computes the modal intensities as a function of azimuth. The roughness measurements were made in about 20 m of water off Panama City, Florida. [Work supported by ONR Code 322 OA.]
Analytic formulation for broadband rough surface and volumetric scattering including matched-filter range resolution
Authors: Huang Wei , Wang Delin , Ratilal Purnima
Published: October 2014

An analytic formulation is derived for the broadband scattered field from a randomly rough surface based on Green's theorem employing perturbation theory. The matched filter is applied to resolve the scattered field within the range resolution footprint of a broadband imaging system. Statistical moments of the scattered field are then expressed in terms of the second moment characterization of the scattering surface. The broadband diffuse reverberation depends on the rough surface spectrum evaluated over a range of wavenumbers, centered at the Bragg wavenumber corresponding to the center frequency of the broadband pulse and extending to wavenumbers proportional to the signal bandwidth. A corresponding analytic broadband volume scattering model is derived from the Rayleigh-Born approximation to Green's theorem.
Multistatic performance prediction for Doppler-sensitive waveforms in a shallow-water environment
Authors: Tollefsen Cristina
Published: October 2014

Navies worldwide are now operationally capable of exploiting multistatic sonar technology. One of the purported advantages of multistatics when detecting directional targets should be the increased probability of receiving a strong reflection at one of the multistatic receivers. However, it is not yet clear (or intuitive) how best to deploy multistatic-capable assets to achieve particular mission objectives. The Performance Assessment for Tactical Systems (PATS) software was recently developed by Maritime Way Scientific under contract to Defence Research and Development Canada as a research tool to assist in exploring different approaches to multistatic performance modelling. Beginning with a user-defined environment and sensor layout, PATS uses transmission loss and reverberation model results to calculate signal excess at each grid point in the model domain. Monte Carlo simulations using many realizations of target tracks allow for the calculation of the cumulative probability of detection as a means to assess performance. Results will be presented comparing the shallow-water performance of monostatic and multistatic sensors using frequency-modulated and Doppler-sensitive waveforms as well as omnidirectional and directional targets in a variety of realistic military scenarios.
Detection and control of cavitation during blood–brain barrier opening: Applications and clinical considerations
Authors: O'Reilly Meaghan A. , Jones Ryan M. , Burgess Alison , Tyson Cassandra , Hynynen Kullervo
Published: October 2014

Microbubble-mediated opening of the blood–brain barrier (BBB) using ultrasound is a targeted technique that provides a transient time window during which circulating therapeutics that are normally restricted to the vasculature can pass into the brain. This effect has been associated with increases in cavitation activity of the circulating microbubbles, and our group has previously described a method to actively control treatments in pre-clinical rodent models based on acoustic emissions recorded by a single transducer. Recently, we have developed a clinical-scale receiver array capable of detecting bubble activity through ex vivo human skullcaps starting at pressure levels below the threshold for BBB opening. The use of this array to spatially map cavitation activity in the brain during ultrasound therapy will be discussed, including considerations for compensating for the distorting effects of the skull bone. Additionally, results from pre-clinical investigations examining safety and therapeutic potential will be presented, and receiver design considerations for both pre-clinical and clinical scale systems will be discussed.
Timing of high intensity pulses for myocardial cavitation-enabled therapy
Authors: Miller Douglas , Dou Chunyan , Owens Gabe E. , Kripfgans Oliver
Published: October 2014

Ultrasound pulses intermittently triggered from an ECG signal can interact with circulating microbubbles to produce myocardial cavitation microlesions, which may enable tissue-reduction therapy. The timing of therapy pulses relative to the ECG was investigated to identify the optimal trigger point with regard to physiological response and microlesion production. Rats were anesthetized, prepared for ultrasound, placed in a heated water bath, and treated with 1.5 MHz focused ultrasound pulses aimed by 8 MHz imaging. Initially, rats were treated for 1 min with triggering at each of six different points in the ECG while monitoring blood pressure. Premature complexes, a useful indicator of efficacy, were seen in the ECG, except during early systole. Premature complexes corresponded with blood pressure pulses for triggering during diastole, but not during systole. Next, triggering at three of the time points, end diastole, end systole, or mid-diastole, was tested for the impact on microlesion creation. Microlesions stained by Evans blue dye were scored in frozen sections. There was no statistically significant variation in cardiomyocyte injury. The end of systole was identified as an optimal trigger time point which yielded ECG complexes and substantial cardiomyocyte injury, but minimal cardiac functional disruption.
Monitoring boiling histotripsy with bubble-based ultrasound techniques
Authors: Khokhlova Vera , Canney Michael , Simon Julianna , Khokhlova Tatiana , Hwang Joo-Ha , Maxwell Adam , Bailey Michael , Sapozhnikov Oleg , Kreider Wayne , Crum Lawrence
Published: October 2014

Cavitation phenomena have been always considered as a predominant mechanism of concern in mechanical tissue damage induced by therapeutic ultrasound. Corresponding methods have been developed to monitor cavitation. Recently, a new high intensity focused ultrasound technology, called boiling histotripsy (BH), was introduced, in which the major physical phenomenon that initiates mechanical tissue damage is vapor bubble growth associated with rapid tissue heating to boiling temperatures. Caused by nonlinear propagation effects and the development of high-amplitude shocks, this tissue heating is localized in space and can lead to boiling within milliseconds. Once a boiling bubble is created, interaction of shock waves with the cavity results in tissue disintegration. While the incident shocks can lead to cavitation phenomena and accompanying broadband emissions, the presence of a millimeter-sized vapor cavity in tissue produces strong echogenicity in ultrasound (US) imaging that can be exploited with B-mode diagnostic ultrasound. Various other methods of imaging boiling histotripsy, including passive cavitation detection (PCD), Doppler or nonlinear pulse-inversion techniques, and high speed photography in transparent gel phantoms are also overviewed. The role of shock amplitude as a metric for mechanical tissue damage is discussed. [Work supported by NIH EB007643, T32DK007779, and NSBRI through NASA NCC 9-58.]
Ultraharmonic intravascular ultrasound imaging with commercial 40 MHz catheter: A feasibility study
Authors: Shekhar Himanshu , Awuor Ivy , Huntzicker Steven , Doyley Marvin M.
Published: October 2014

The abnormal growth of the vasa vasorum is characteristic of life-threatening atherosclerotic plaques. Intravascular ultraharmonic imaging is an emerging technique that could visualize the vasa vasorum and help clinicians identify life-threatening plaques. Implementing this technique on commercial intravascular ultrasound (IVUS) systems could to accelerate its clinical translation. Our previous work has demonstrated ultraharmonic IVUS imaging with a modified clinical system that was equipped with a commercial 15 MHz peripheral imaging catheter. In the present study, we investigated the feasibility of ultraharmonic imaging with a commercially available 40 MHz coronary imaging catheter. We imaged a flow phantom that had contrast agent microbubbles (Targestar-P-HF, Targeson Inc., CA) perfused in side channels parallel to its main lumen. The transducer was excited at 30 MHz using 10% bandwidth chirp-coded pulses. The ultraharmonic response at 45 MHz was isolated and preferentially visualized using pulse inversion and digital filtering. Side channels with 900 μm and 500 μm diameter were detected with contrast-to-tissue ratios approaching 10 dB for clinically relevant microbubble concentrations. The results of this study indicate that ultraharmonic imaging is feasible with commercially available coronary IVUS catheters, which may facilitate its widespread application in preclinical research and clinical imaging.
A method to calibrate the absolute receive sensitivity of spherically focused, single-element transducers
Authors: Rich Kyle T. , Mast T. Douglas
Published: October 2014

Quantitative acoustic measurements of microbubble behavior, including scattering and emissions from cavitation, would be facilitated by improved calibration of transducers making absolute pressure measurements. In particular, appropriate methods are needed for wideband calibration of focused passive cavitation detectors. Here, a substitution method was developed to characterize the absolute receive sensitivity of two spherically focused, single-element transducers (center transmit frequencies 4 and 10 MHz). Receive calibrations were obtained by transmitting and receiving a broadband pulse between the two focused transducers in a pitch-catch, confocally aligned configuration, separated by a distance equal to the sum of the two focal lengths. A calibrated hydrophone was substituted to measure the pressure field in the plane of each receiver’s surface. The frequency dependent receive sensitivity at the focus was then calculated for each transducer as the ratio of the receiver-measured voltage and the average hydrophone-measured pressure amplitude across the receiver surface. Calibrations were validated by generating an approximately spherically spreading, broadband pressure wave at the focus of each transducer using a 2-mm diameter transducer and comparing the absolute acoustic pressure measured by each focused transducer to that measured by a calibrated hydrophone.
Traffic monitoring with noise: Investigations on an urban seismic network
Authors: Riahi Nima , Gerstoft Peter
Published: October 2014

Traffic in urban areas generates not only acoustic noise but also much seismic noise. The latter is typically not perceptible by humans but could, in fact, offer an interesting data source for traffic information systems. To explore the potential for this, we study a 5300 geophone network, which covered an area of over 70 km2 in Long Beach, CA, and was deployed as part of a hydrocarbon industry survey. The sensors have a typical spacing of about 100 m, which presents a two-sided processing challenge here: signals beyond a few receiver spacings from the sources are often strongly attenuated and scattered whereas nearby receiver signals may contain complicated near-field effects. We illustrate how we address this issue and give three simple applications: counting cars on a highway section, classifying different types of vehicles passing along a road, and measuring time and take-off velocity of aircraft at Long Beach airport. We discuss future work toward traffic monitoring and also possible connections with acoustical problems.
Acoustic absorption of green roof samples commercially available in southern Brazil
Authors: Brum Ricardo , Paul Stephan , da Silva Andrey R. , Piovesan Tenile
Published: October 2014

Previous investigations have shown that green roofs provide many environmental benefits, such as thermal conditioning, air cleaning, and rain water absorption. Nevertheless, information regarding acoustic properties, such as sound absorption and transmission loss is still sparse. This work presents measurements of the sound absorption coefficient of two types of green roofs commercially available in Brazil: the alveolar and the hexa system. Measurements were made in a reverberant chamber according to ISO-354 for different variations of both systems: the alveolar system with 2.5 cm of substrate with and without grass and 4 cm of substrate only. The hexa system was measured with layers of 4 and 6 cm of substrate without vegetation and 6 cm of substrate with a layer of vegetation of the sedum type. For all systems, high absorption coefficients were found for medium and high frequency limits (α ≈ 0.7) and low absorption in low frequencies (α ≈ 0.2). This was expected due to the highly porous structure of the substrate. The results suggest that the types of green roofs evaluated in this work could be a good approach to noise control in urban areas.
Is age-related hearing loss predominantly metabolic?
Authors: Withnell Robert H. , Ueberfuhr Margarete A.
Published: October 2014

Studies in animals have shown that age-related hearing loss is predominantly metabolic in origin. In humans, direct access to the cochlea is not usually possible and so non-invasive methods of assessing cochlear mechanical function are required. This study used a non-invasive assay of cochlear mechanical function, otoacoustic emissions, to examine a metabolic versus hair-cell-loss origin for age-related hearing loss. Three subject groups were examined: adult females with clinically normal hearing, adult females with age-related hearing loss, and adult males with noise-induced hearing loss. Contrasting otoacoustic emission input-output functions were obtained for the three groups, suggesting a causal relationship between age-related hearing loss and strial dysfunction.
Further modeling of temporal effects in two-tone suppression
Authors: Hegland Erica L. , Strickland Elizabeth A.
Published: October 2014

Two-tone suppression, a nearly instantaneous reduction in cochlear gain and a by-product of the active process, has been extensively studied both physiologically and psychoacoustically. Some physiological data suggest that the medial olivocochlear reflex (MOCR), which reduces the gain of the active process in the cochlea, may also reduce suppression. The interaction of these two gain reduction mechanisms is complex and has not been widely studied or understood. Therefore, a model of the auditory periphery that includes the MOCR time course was used to systematically investigate this interaction of gain reduction mechanisms. This model was used to closely examine two-tone suppression at the level of the basilar membrane using suppressors lower in frequency than the probe tone. Results were compared both with and without elicitation of the MOCR. Preliminary results indicate that elicitation of the MOCR reduces two-tone suppression when measured as the total basilar membrane response at the characteristic frequency (CF) of the probe. The purpose of this study was to investigate further by separating the frequency components of the basilar membrane response at CF to determine the excitation produced by the probe and by the suppressor with and without MOCR elicitation. [Research supported by NIH(NIDCD)R01 DC008327 and T32 DC00030.]
Baseline neurophysiological noise levels in children with auditory processing disorder
Authors: Nagao Kyoko , Greenwood L. Ashleigh , Sheth Raj C. , Gaffney Rebecca G. , Cardinale Matthew R. , Morlet Thierry
Published: October 2014

The current study examined the baseline neurophysiological responses between children with auditory processing disorder (APD) and the control group. Auditory event related potentials were recorded in 23 children with APD (ages 7–12 years, mean age = 8.9 years) and 25 age-matched control children in response to a /da/ presented to each ear separately (right and left ear conditions). A no-sound condition was recorded as well. Baseline neurophysiological activity was measured as the root mean square amplitude of the 100 ms pre-stimulus period. Preliminary analysis of data from 19 children with APD and 13 controls indicated that the APD group showed significantly greater pre-stimulus amplitude than the control group in the left ear condition, F(1, 30) = 4.415, p = 0.044, but we did not find significant group differences in the no-sound and right ear conditions, F(1, 30) = 2.237, p = 0.15 and F(1, 30) = 0.088, p = 0.77, respectively. The results suggest that children with APD may need a longer time period to return to a resting state than control children when the left ear is stimulated. Hence, these results may indicate asymmetrical neural activities of the auditory pathways in APD.
Duration perception of time-varying sounds: The role of the amplitude decay and rise-time modulator
Authors: Chuen Lorraine , Schutz Michael
Published: October 2014

It is well known that ramped (rising energy) sounds are perceived as longer in duration than damped (falling energy) sounds that are time-reversed, but otherwise identical versions of one another (Schlauch, Ries & DiGiovanni, 2001; Grassi & Darwin, 2006). This asymmetry has generally been attributed to the under-estimation of damped sound duration, rather than the over-estimation of ramped sound duration. As previous literature most commonly employs exponential amplitude modulators, in the present experiment, we investigate whether altering the nature of this amplitude decay- or rise-time modulator (linear or exponential) would influence this typically observed perceptual asymmetry. Participants performed an adaptive, 2AFC task that assessed the point of subjective equality (PSE) between a standard tone with a constant ramped/damped envelope, and a comparator tone with a “flat,” steady state envelope whose duration varied according to a 1-up, 1-down rule. Preliminary results replicated previous findings that ramped sounds are perceived as longer than their time-reversed, damped counterparts. However, for sounds with a linear amplitude modulator, this perceptual asymmetry is partially accounted for by ramped tone over-estimation, contrasting previous findings in the literature conducted with exponential amplitude modulators.
Relationship between gap detection thresholds and performance on the Advanced Measures of Music Audiation Test
Authors: Hoch Matthew , Blumsack Judith , Soles Lindsey
Published: October 2014

Considerable neurophysiological, neural imaging, and behavioral research indicates that auditory processing in musicians differs from that of non-musicians (e.g., Musacchia et al., 2007; Ohnishi et al., 2001; Pantev et al., 1998; Parbery-Clark, 2009). Among the auditory skills in musicians that have been studied are gap detection measures of temporal acuity (Mishra & Panda, 2014; Payne, 2012). These studies typically have compared the gap detection thresholds of musicians and non-musicians. The present work relates gap detection performance to musical aptitude rather than to reported musical training history. In addition, in the present study, gap detection was measured under two different stimulus conditions: the within-channel (WC) condition (in which the sound that precedes the gap is spectrally identical to the sound following the gap) and the across-channel (AC condition) (in which the pre- and post-gap sounds are spectrally different. Results indicate a significant correlation between across-channel gap detection thresholds and musical aptitude and no correlation between within-channel performance and musical aptitude. These results have important implications for temporal acuity as it relates to musical aptitude.
Modeling response times to analyze perceptual interactions in complex non-speech perception
Authors: Silbert Noah H. , Houpt Joseph W.
Published: October 2014

General recognition theory (GRT) provides a powerful framework for modeling interactions between perceptual dimensions in identification-confusion data. The linear ballistic accumulator (LBA) model provides powerful methods for analyzing multi-choice (2 + ) response time (RT) data as a function of evidence accumulation and response thresholds. We extend (static) GRT to the domain of RTs by fitting LBA models to RTs collected in two auditory GRT experiments. Although the mapping between the constructs of GRT (e.g., perceptual separability, perceptual independence) and the components of the LBA (e.g., drift rates, response thresholds) is complex, the dimensional interactions defined in GRT can be indirectly addressed in the LBA framework by testing for invariance of LBA parameters across appropriate subsets of the data. The present work focuses on correspondences between (invariance of) parameters in LBA and perceptual separability and independence in GRT.
Testing the contribution of spectral cues on pitch strength judgments in normal-hearing listeners
Authors: Shofner William , Marsteller Marisa
Published: October 2014

When a wideband harmonic tone complex (wHTC) is passed through a noise vocoder, the resulting sounds can have harmonic structures with large peak-to-valley ratios in the spectra, but little or no periodicity strength in the autocorrelation functions. Noise-vocoded wHTCs evoke simultaneous noise percepts and pitch percepts similar to those evoked by iterated rippled noises. We have previously shown that spectral cues do not appear to control behavioral responses of chinchillas to noise-vocoded wHTCs in a stimulus generalization task, but do appear to contribute to pitch strength judgments in normal-hearing listeners for noise-vocoded wHTCs relative to non-vocoded wHTCs. To further test the role of spectral cues, normal-hearing listeners judged the pitch strengths of noise-vocoded wHTCs relative to infinitely-iterated rippled noise (IIRN). Stimuli had harmonic structures with a fixed fundamental frequency of 500 Hz and were presented monaurally at 50 dB SL. Listeners’ judgments of pitch strength evoked by vocoded wHTCs were generally consistent with peak-to-valley ratios of the stimuli. In order to reduce spectral cues and resolvability, stimuli were high-passed filtered. Pitch strength judgments of vocoded wHTCs were reduced following high-pass filtering. These findings suggest that spectral cues do contribute to pitch perception in human listeners.
Loudness of a multi-tonal sound field, consisting of either one two-component complex sound source or two simultaneous spatially distributed sound sources
Authors: Vannier Michaël , Parizet Etienne
Published: October 2014

The aim of the present study is to provide new elements about the perceived loudness of stationary complex sound fields and test the validity of current models under such conditions. The first part consisted in testing the hypothesis according which the directional loudness of a multi-component sound source could be fully explained by the directional loudness of each of its single components. In this way, the directional loudness sensitivities of a two-component complex sound source (third-octave noise bands centered at 1 kHz and 5 kHz) have been measured in the horizontal plane. Despite a previous equalization in loudness of each component to a frontal reference, a small effect of the azimuth angle on loudness still remained, partly disproving the assumption. In a second part, the influence of the spatial distribution of two sound sources on the global loudness was investigated (with the same two narrow-band noises). No effect has been found by Song (2007) for small incidence angles (10 and 30°). The present experiment extends this result for wide incidence angles and so, under highly dichotic listening situations. Finally, all the subjective data have been compared with the predictions from different models of loudness, and the results will be discussed.
An approach to the analysis of relations between syllable and sentence perception in quiet and noise in the Speech Perception Assessment and Training System: Preliminary results for ten hearing-aid users
Authors: Miller James D.
Published: October 2014

Logistic functions relating abilities to indentify syllable onsets, nuclei, and codas in quiet and noise as a function of snr are measured. Syllable perception is the product of these individual abilities. It is found that syllable perception in noise is highly correlated with syllable perception quiet. The relation of sentence perception in the SPATS sentence task with SPATS syllable constituent perception is examined. As shown years ago at the Bell Labs, only modest levels of syllable identification are needed to support nearly perfect levels of sentence perception. Here, it is found that sentence perception in quiet and noise is correlated with syllable perception in quiet, the use of inherent context provided by syllable perception (Boothroyd and Nittrauer (1988)), and with the use of situational context, independent of syllable perception. Finally, the effects of speech perception training on these relations are examined for each of the ten hearing-aid users studied. [Work supported by NIH/NICD Grant R21/R33DC011174 “Multi-site Study of the Efficacy of Speech Perception Training for Hearing-Aid Users,” C. S. Watson, PI. Data supplied by cooperating sites: Medical University of South Carolina, J. Dubno, Site PI; University of Memphis, D. Wark, Site PI; and University of Maryland, S. Gordon-Salant, Site PI.]
Tempo-based segregation of spoken sentences
Authors: Kidd Gary R. , Humes Larry E.
Published: October 2014

The ability to make use of differences in speech rhythms to selectively attend to a single spoken message in a multi-talker background was examined in a series of studies. Sentences from the coordinate response measure corpus provided a set of stimuli with a common rhythmic framework spoken by several talkers at similar speaking rates. Subjects were asked to identify two key words spoken in a “target” sentence identified by a word (call sign) near the beginning of the sentence. The target talker was always in the same male voice and either two or six background talkers were presented in different voices (half male and half female). The rate of the background talkers was manipulated to create natural sounding speech that preserved the original pitch and speech rhythms at faster and slower speaking rates. Unaltered target sentences were presented in the presence of faster, unaltered, or slower competing sentences. Performance was poorest with matching target and background tempos, with substantial increases in performance as the tempo differences increased. Modification of the target-sentence rate confirmed that the effect is due to the relative timing of target and background speech, rather than the properties of rate-modified background speech. [Work supported by NIH-NIA.]
Effects of depression on speech
Authors: Sahu Saurabh , Espy-Wilson Carol
Published: October 2014

In this paper, we are investigating the effects of depression on speech. The motivation comes from the fact that neuro-physiological changes associated with depression affect motor coordination and can disrupt the articulatory precision in speech. We use the database collected by Mundt et al. (J. Neurolinguist. vol. 20, no. 1, pp. 50–64, Jan. 2007) in which 35 subjects were treated over a 6 week period and study how the changes in mental state are manifest in certain acoustic properties that correlate with the Hamilton Depression Rating Scale (HAM-D), which is a clinical assessment score. We look at features such as the modulation frequencies, aperiodic energy during voiced speech, vocal fold jitter and shimmer, and other cues that are related to articulatory precision. These measures will be discussed in detail.
Linear and non-linear acoustic voice analysis of Persian speaking Parkinson's disease patients
Authors: Majdinasab Fatemeh , Mollashahi Maryam , Vali Mansour , Hashemi Hedieh
Published: October 2014

Purpose: Many studies have analyzed acoustic voice characteristics (AVC) of Parkinson's disease patients (PDP) by linear or non-linear methods. The aim of this study is to compare the linear and non-linear approaches in acoustic voice analysis of Persian speaking PDPs. Method: This cross sectional, non-experimental study was done on 27 (15 males, 12 females) PDP and 21 healthy age-sex matched subjects (11 males, 10 females). Patients were chosen from attendants of movement disorders clinic using convenience sampling. All of patients evaluated in "on" medication period. AVC consisting average fundamental frequency (f0), standard deviation of f0, mean percentage of jitter, shimmer, and HNR in prolongation of all Persian vowels /a, e, i, o, u /. Praat 5.1.17 software (as a linear tool) and Matlab (as a non-linear method) used to evaluate AVC. Result: There was not any significant difference between PDPs and normal subjects except for jitter /æ /(0.041) and / e/ (0.021). According to non-linear characteristics of Wavelet entropy coefficient, and by mother wavelet with coif1 (in Matlab), all of AVC of patients differentiated from normal. Conclusion: It seems that non-linear analysis is more detailed method to discriminate dysarthric voice from normal voice. Keywords: Acoustic voice analysis, Parkinson's disease, linear, nonlinear.
Prosodic characteristics in young children with autism spectrum disorder
Authors: Dilley Laura , Cook Sara , Stockman Ida , Ingersoll Brooke
Published: October 2014

The prosody of high-functioning adults and adolescents with autism spectrum disorder (ASD) has been reported to differ from that of typically developing individuals. The present study investigated whether young children under eight years old with ASD differ in prosodic characteristics compared with neurotypical children matched on expressive language ability. Seven children with ASD (38–93 months) and seven neurotypical children (20–30 months) were recorded during naturalistic interactions with a parent. Naïve listeners (n = 18) were recruited to rate utterances for: (i) age, (ii) percentage of intelligible words, (iii) pitch, (iv) speech rate, (v) degree of animation, and (vi) certainty of diagnosis. An acoustic analysis was also conducted of speech rate and fundamental frequency (F0). Results of the rating task showed no statistically significant difference on any measure except estimated age. However, children in the ASD group had a significantly lower mean, maximum, and minimum F0 than children in the control group; there was no significant difference between groups for speech rate. These findings may indicate that speech characteristics alone are unlikely to be a sufficient early sign of an ASD diagnosis.
Objective speech intelligibility prediction in sensorineural hearing loss using acoustic simulations and perceptual speech quality measures
Authors: Chiaramello Emma , Moriconi Stefano , Tognola Gabriella
Published: October 2014

A novel approach to objectively predict speech intelligibility in sensorineural hearing loss using acoustic simulations of impaired perception and objective measures of perceptual speech quality (PESQ) is proposed and validated. Acoustic simulations of impaired perception with different types and degrees of hearing loss were obtained degrading of the original speech waveforms by spectral smearing, expansive nonlinearity, and level scaling. The CUNY NST syllables were used as test material. PESQ was used to measure perceptual quality of the acoustic simulations thus obtained. Finally, PESQ scores were transformed into predicted intelligibility scores using a logistic function. Validation of the proposed objective method was performed by comparing predicted intelligibility scores with subjective measures of intelligibility of the degraded speech in a group of ten subjects. Predictive intelligibility scores showed good correlation (R2 = 0.7) with subjective intelligibility scores and a low error in the prediction (RMSE = 0.14). The proposed approach could be a valuable aid in real clinical applications where it is needed to measure speech intelligibility and might be of some help in avoiding time-consuming experimental measurements. In particular, this method might be valuable in the characterization of the sensitivity of new speech tests for screening and diagnosing of hearing loss, or in the assessment of the performance of novel algorithms of speech enhancement for a target hearing impairment.
Effect of formant characteristics on older listeners’ dynamic pitch perception
Authors: Shen Jing , Wright Richard , Souza Pamela
Published: October 2014

Previous research suggested a large inter-subject variability in dynamic pitch perception among older individuals (Souza et al., 2011). Although data from younger listeners with normal hearing indicate temporal and spectral variations in complex formant characteristics may influence dynamic pitch perception (Green et al., 2002), the present study examines this interaction in an aging population. The stimulus set includes two monophthongs that have static formant patterns and two diphthongs that have dynamic formant patterns. The fundamental frequency at the midpoint in time of each vowel is kept consistent, while the ratio of start-to-end frequency varies in equal logarithmic steps. Older adults with near-normal hearing are tested using an identification task, in which they are required to identify the pitch glide as either “rise” or “fall.” An experimental task of AX discrimination is also included to verify the identification data. Results to date show inter-subject variability in dynamic pitch perception among listeners with good static pitch perception. Better pitch glide perception with monophthong than diphthong is observed in those individuals who perform poorly in general. The findings suggest a connection between individual abilities to perceive dynamic pitch and to extract the cues from fundamental and formant frequencies. [Work supported by NIH.]
Ocean dynamics and numerical modeling of canyons and shelfbreaks
Authors: Lermusiaux Pierre F. , Haley Patrick , Mirabito Chris , Duda Timothy , Gawarkiewicz Glen
Published: October 2014

Multiscale ocean dynamics and multi-resolution numerical modeling of canyons and shelfbreaks are outlined. The dynamics focus is on fronts, currents, tides, and internal tides/waves that occur in these regions. Due to the topographic gradients and strong internal field gradients, nonlinear terms and non-hydrostatic dynamics can be significant. Computationally, a challenge is to achieve accurate simulations that resolve strong gradients over dynamically significant space- and time-scales. To do so, one component are high-order schemes that are more accurate for the same efficiency than lower-order schemes. A second is multi-resolution grids that allow optimized refinements, such as reducing errors near steep topography. A third are methods that allow to solve for multiple dynamics, e.g., hydrostatic and non-hydrostatic, seamlessly. To address these components, new hybridizable discontinuous Galerkin (HDG) finite-element schemes for (non)-hydrostatic physics including a nonlinear free-surface are introduced. The results of data-assimilative multi-resolution simulations are then discussed, using the primitive-equation MSEAS system and telescoping implicitly two-way nested domains. They correspond to collaborative experiments: (i) Shallow Water 06 (SW06) and the Integrated Ocean Dynamics and Acoustics (IODA) research in the Middle Atlantic Bight region; (ii) Quantifying, Predicting and Exploiting Uncertainty (QPE) in the Taiwan-Kuroshio region; and (iii) Philippines Straits Dynamics Experiment (PhilEx).
Internal tides in canyons and their effect on acoustics
Authors: Duda Timothy F. , Zhang Weifeng G. , Lin Ying-Tsong , Ponte Aurelien
Published: October 2014

Internal gravity waves of tidal frequency are generated as the ocean tides push water upward onto the continental shelf. Such waves also arrive at the continental slope from deep water and are heavily modified by the change in water depth. The wave generation and wave shoaling effects have an additional level of complexity where a canyon is sliced into the continental slope. Recently, steps have been taken to simulate internal tides in canyons, to understand the physical processes of internal tides in canyons, and also to compute the ramifications on sound propagation in and near the canyons. Internal tides generated in canyons can exhibit directionality, with the directionality being consistent with an interesting multiple-scattering effect. The directionality imparts a pattern to the sound-speed anomaly field affecting propagation. The directionality also means that short nonlinear internal waves, which have specific strong effects on sound, can have interesting patterns near the canyons. In addition to the directionality of internal tides radiated from canyons, the internal tide energy within the canyons can be patchy and may unevenly affect sound.
South China Sea upper-slope sand dunes acoustics experiment
Authors: Chiu Ching-Sang , Reeder Ben , Chiu Linus , Yang Yiing Jang , Chen Chifang
Published: October 2014

Very large subaqueous sand dunes were discovered on the upper continental slope of the Northeastern South China Sea. The spatial distribution and scales of these large sand dunes were mapped by two multibeam echo sounding (MBES) surveys, one in 2012 and the other in 2013. These two surveys represented two pilot cruises as part of a multiyear, US-Taiwan collaborative field study designed to characterize these sand dunes, the associated physical processes and the associated acoustic scattering physics. The main experiment will be carried out in 2014. The combination of MBES, coring and acoustic transmission data obtained from the two pilot cruises have provided vital initial knowledge of (1) the spatial and temporal scales of the sand dunes from objective analysis, (2) the geoacoustic properties of the dunes based on forward modeling to matching the measured levels, and (3) the anisotropy and translational variability of the transmission loss based on a signal energy analysis of the repeated 1–2 kHz and 4–6 kHz FM signals transmitted by a calibrated sound source towed along two circular tracks, each surrounding a receiver. The results from the pilot cruises are presented and discussed. [The research is sponsored by the US ONR and the Taiwan NSC.]
Formation sparse aperture antenna arrays based on the sequence Costas
Authors: Anikin Igor I.
Published: October 2014

To obtain high spatial resolution in sonar, ultrasonic image, radar, seismic, and radio astronomy use active antenna arrays that contain a large number of elements. To reduce the cost of such an antenna arrays used with sparse aperture. In this approach, the antenna array is partitioned into several subarrays. Geometric size subarray equivalent equidistant placement Nc * Nc elements. Subarrays filled Nc elements arranged according to the sequence Costas Nc-th order. Each filled subarrays own Costas sequence. As a result, the number of elements in the array is reduced in times Nc. Form the beam pattern in the main sections close to the plane shape of the beam pattern of equidistant antenna array, and the directivity factor is almost independent of frequency band. The upper frequency is reduced in the directivity factor (π·Nc)/2 times as compared with the plane equidistant antenna array. Using a decaying distribution can be reduced in amplitude level of the side lobe in the principal planes. Thus, by setting the order of the Costas sequence can in each case to optimize the degree of reduction of the number of elements in the array antenna at a predetermined directivity factor.
Simplex underwater acoustic communications using passive time reversal
Authors: Sun Lin , Li Haisen , Zou Bo , Li Ruo
Published: October 2014

The spatial-temporal compression, which is achieved through using simple time reversal (TR) process, can reduce the inter-symbol interference and increase the signal strength. The active TR needs two-way propagation, so it cannot be used in simplex underwater acoustic communications. Based on the one-way propagation property of passive TR, a simplex underwater acoustic communication method using passive TR is proposed. The proposed method is considered in two scenarios: uplink transmission from a single send-only element to an array and downlink transmission from an array to a single receive-only element. The principle of proposed method is analyzed in theory and the performance of proposed method is verified through experiment. Results demonstrate that passive TR process can improve the output signal-to-noise ratio and decrease the bit error rate, so the performance of proposed method is superior to that of simplex acoustic communication method without using passive TR.
Predation by Myxococcus xanthus Induces Bacillus subtilis To Form Spore-Filled Megastructures
Authors: Müller Susanne , Strack Sarah N. , Ryan Sarah E. , Kearns Daniel B. , Kirby John R.
Published: October 2014

Biofilm formation is a common mechanism for surviving environmental stress and can be triggered by both intraspecies and interspecies interactions. Prolonged predator-prey interactions between the soil bacterium
Myxococcus xanthus
and
Bacillus subtilis
were found to induce the formation of a new type of
B. subtilis
biofilm, termed megastructures. Megastructures are tree-like brachiations that are as large as 500 μm in diameter, are raised above the surface between 150 and 200 μm, and are filled with viable endospores embedded within a dense matrix. Megastructure formation did not depend on TasA, EpsE, SinI, RemA, or surfactin production and thus is genetically distinguishable from colony biofilm formation on MSgg medium. As
B. subtilis
endospores are not susceptible to predation by
M. xanthus
, megastructures appear to provide an alternative mechanism for survival. In addition,
M. xanthus
fruiting bodies were found immediately adjacent to the megastructures in nearly all instances, suggesting that
M. xanthus
is unable to acquire sufficient nutrients from cells housed within the megastructures. Lastly, a
B. subtilis
mutant lacking the ability to defend itself via bacillaene production formed megastructures more rapidly than the parent. Together, the results indicate that production of the megastructure facilitates
B. subtilis
escape into dormancy via sporulation.
Siderophore-Mediated Iron Acquisition Influences Motility and Is Required for Full Virulence of the Xylem-Dwelling Bacterial Phytopathogen Pantoea stewartii subsp. stewartii
Authors: Burbank Lindsey , Mohammadi Mojtaba , Roper M. Caroline
Published: October 2014

Iron is a key micronutrient for microbial growth but is often present in low concentrations or in biologically unavailable forms. Many microorganisms overcome this challenge by producing siderophores, which are ferric-iron chelating compounds that enable the solubilization and acquisition of iron in a bioactive form.
Pantoea
stewartii
subsp.
stewartii
, the causal agent of Stewart's wilt of sweet corn, produces a siderophore under iron-limiting conditions. The proteins involved in the biosynthesis and export of this siderophore are encoded by the
iucABCD-iutA
operon, which is homologous to the aerobactin biosynthetic gene cluster found in a number of enteric pathogens. Mutations in
iucA
and
iutA
resulted in a decrease in surface-based motility that
P. stewartii
utilizes during the early stages of biofilm formation, indicating that active iron acquisition impacts surface motility for
P. stewartii
. Furthermore, bacterial movement
in planta
is also dependent on a functional siderophore biosynthesis and uptake pathway. Most notably, siderophore-mediated iron acquisition is required for full virulence in the sweet corn host, indicating that active iron acquisition is essential for pathogenic fitness for this important xylem-dwelling bacterial pathogen.
Transmission and Persistence of Livestock-Associated Methicillin-Resistant Staphylococcus aureus among Veterinarians and Their Household Members
Authors: Bosch T. , Verkade E. , van Luit M. , Landman F. , Kluytmans J. , Schouls L. M.
Published: October 2014

After the first isolation of livestock-associated methicillin-resistant
Staphylococcus aureus
(LA-MRSA) in 2003, this MRSA variant quickly became the predominant MRSA obtained from humans as part of the Dutch national MRSA surveillance. Previous studies have suggested that human-to-human transmission of LA-MRSA, compared to that of other MRSA lineages, rarely occurs. However, these reports describe the transmission of LA-MRSA based on epidemiology and limited molecular characterization of isolates, making it difficult to assess whether transmission actually occurred. In this study, we used whole-genome maps (WGMs) to identify possible transmission of LA-MRSA between humans. For this, we used LA-MRSA isolates originating from a 2-year prospective longitudinal cohort study in which livestock veterinarians and their household members were repeatedly sampled for the presence of
S. aureus
. A considerable degree of genotypic variation among LA-MRSA strains was observed. However, there was very limited variability between the maps of the isolates originating from the same veterinarian, indicating that each of the veterinarians persistently carried or had reacquired the same LA-MRSA strain. Comparison of WGMs revealed that LA-MRSA transmission had likely occurred within virtually every veterinarian household. Yet only a single LA-MRSA strain per household appeared to be involved in transmission. The results corroborate our previous finding that LA-MRSA is genetically diverse. Furthermore, this study shows that transmission of LA-MRSA between humans occurs and that carriage of LA-MRSA can be persistent, thus posing a potential risk for spread of this highly resistant pathogen in the community.