bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental determination of the complex Poisson’s ratio of viscoelastic materials.
Authors: Guillot François M. , Trivett D. H.
Published: July 2011

An empirical procedure to determine the dynamic, complex Poisson’s ratio of viscoelastic materials as a function of temperature and hydrostatic pressure is presented. In this procedure, the Young’s modulus and the bulk modulus of the material are measured, and the complex values of these moduli are combined to compute Poisson’s ratio. The two independent measurement systems used to obtain these data are described. The Young’s modulus system requires a sample cut in the shape of a bar and relies on traditional resonance measurements for low-frequency data as well as on wave speed measurements for higher-frequency data; measurements are performed in air. The bulk modulus system measures the dynamic compressibility of a sample of arbitrary shape immersed in Castor oil. Data can be obtained at frequencies typically ranging from 50 Hz to 5 kHz, at temperatures comprised between -2 and 50° C and under hydrostatic pressures ranging from 0 to 2 MPa (Young’s) or 6.5 MPa (bulk). The two moduli can also be combined to compute any other modulus, and the two systems therefore allow the complete elastic characterization of a homogeneous and isotropic material. Data obtained on a nearly incompressible rubber are presented.
Measurement of planar poisson’s ratio for piezoceramic disks.
Authors: Libov Dmytro , Meleshko Viatcheslav
Published: July 2011

Previous methods for a determination of a planar Poisson’s ratio in ferroelectric ceramic disks were proposed for thin disks. If a thickness of a disk strongly affects the vibrations, we get error in determination of Poisson’s ratio in usage 1-D theory of disk vibrations. Planar Poisson’s ratio in this work has been determined from an overtone method and a resonant method for a thick piezoceramic disk. The theoretical and the experimental contour modes with different types of vibrations symmetry have been compared in the resonant method. For the first theoretical contour mode the thickness correction was applied. The first order contour resonant frequency was determined in the experiment after the cutting of split electrodes. The overtone method is based on the solution of three-dimensional problem of vibrations of a finite cylinder. Only one experiment is needed in the overtone method. The obtained results have been compared with the handbook data. It may be concluded that the proposed methods provide an accurate determination of planar Poisson’s ratio in thick piezoelectric ceramic disks, when all experimentally measurements were made on the single piece of the piezoceramic material.
Some optical methods for modal analysis of musical instruments.
Authors: Rossing Thomas D.
Published: July 2011

Because of their high spatial resolution, optical methods have become important for modal analysis of vibrations in musical instruments. Among optical methods for modal analysis are time-average holographic interferometry, pulsed TV holography, disital speckle interferometry, and scanning vibrometry. We review briefly principles and applications of optical methods for modal analysis.
Pitfalls of time resolved electronic speckle pattern interferometry.
Authors: Kausel Wilfried
Published: July 2011

Electronic speckle pattern interferometry has turned out to be a method for steady state analysis of vibrating surfaces, which is easy to use and does not require an expensive setup. A new generation of digital high-speed cameras has now become available, which is significantly cheaper, faster, and more sensitive than prior generations, awakening the desire to study transient behavior interferometrically. Although it seems quite straightforward to do a quasi-static ESPI deformation analysis at frame rates of 10–30 fps, it is, in fact, not. From four different types of state of the art digital high-speed cams, all of them with datasheet specifications which should have made them well suited for the intended purpose, only one was able to produce recordings with satisfactory interferences. Recordings of all tested cameras will be presented and possible explanations for the interference problem will be discussed. A successful application of time-resolved ESPI to a plugged or struck musical instrument will also be demonstrated.
Experimental study of vibraphone pitch bending using electronic speckle-pattern interferometry.
Authors: Worland Randy
Published: July 2011

Pitch bending on the vibraphone is an extended performance technique called for by modern composers dating back to the 1960s. After first striking the middle of a bar with a soft mallet in the normal manner, the pitch bend is obtained by pressing a hard mallet onto the bar at a nodal point and then sliding it away from the node as the note sustains. The audible result is a descending pitch, typically of about one semitone. Experimental data showing frequency vs location of the hard mallet al.ong the bar are presented and interpreted with the use of time-averaged electronic speckle-pattern interferograms showing the vibrational modes of the vibraphone bar. Frequency vs mallet mass data are also presented and discussed. In addition, it is shown that for some combinations of mallet type and vibrational mode this technique can produce an increase in frequency.
Mode studies in a triangular bell plate.
Authors: Hansen Uwe J. , Garner John
Published: July 2011

Triangular bell plates have been used as the poor man’s substitute for hand-bells. As in other pitched percussion instruments, pitch identification largely depends on the harmonic relation between the most significant overtones. This work reports on experimental mode studies of a bell plate using electronic holographic interferometry and impact excited modal analysis. Experimental results are also compared with finite element mode calculations. The finite element calculations are in good agreement with the experimental data.
Spatial variation of natural ambient sound pressure levels in Rocky Mountain National Park.
Authors: Mennitt Daniel J.
Published: July 2011

The soundscape is a critical component of an ecological community, and knowledge of natural ambient sound pressure levels is crucial to assessing impacts of noise. However, the spatial correlation of natural ambient sound pressure levels is largely unknown and a given measurement may not be representative of the locale. Much anthropogenic noise can be considered point or line sources; the spatial correlation of the resulting sound pressure levels can be completely described by directivity and the inverse square law in an isotropic medium. However, most natural sources (wind, birdsong, rain, insects, etc.) may be better described in aggregate as an irregular source with stochastic characteristics. Recently, a 9-day long study collected continuous audio data at 18 locations over a roughly 3.5 s km1 area in Rocky Mountain National Park. Analysis seeks to investigate the spatial variation of natural ambient sound pressure level measurements and the degree to which they are correlated across space. Results will suggest how sparsely an area can be measured as well as placement of a finite number of microphones to best observe the acoustical environment.
Automatically separating anthropogenic from natural sounds in parks.
Authors: Gillette Jack , Schomer Paul
Published: July 2011

The National Park Service needs to determine the extent of both man-made and natural sounds in national parks. To do this, they need to separate anthropogenic noises from natural ones. To be accurate, this requires hundreds of hours of sound data spread out over times of day, days of the week, and seasons, and must be spatially sufficient. With these much data to analyze, manual listening for audible tones and noises can be an impossible task. However, with a program that uses an algorithm to search for anthropogenic sounds, the task becomes much easier. Our hypothesis is that all anthropogenic noises except for jet aircraft will include tones below 1000 Hz. Our main purpose is to write software that flags anthropogenic sounds below 1000 Hz. Because anthropogenic and natural sounds are uncorrelated, we hope to flag virtually all anthropogenic sounds at the cost of falsely flagging some natural sounds. Furthermore, we can very accurately estimate the ALEQ for a given length of time based on a much smaller sample and then subtract that from the total to find the ALEQ for the anthropogenic sound. This paper discusses the development and testing of this process.
Modeling hikers’ exposure to transportation noise in national parks and wilderness.
Authors: Kaliski Kenneth , Lawson Steve , Pettebone David , Newman Peter , Duncan Eddie , Kiser Brett , Talbot Eric , Eros Emily
Published: July 2011

Results of research conducted in a variety of national park settings suggest that the quality of visitors’ experiences is tied to the naturalness of the area’s soundscape. Yet, visitor use in national parks tends to be concentrated in areas that are accessible or close to roads. As a result, surface transportation noise can significantly affect visitor experience quality. This paper describes tools and methods used to estimate the effects of various transportation planning options on hikers’ noise exposure in national parks. These tools combine transportation noise mapping with GPS tracking and computer modeling of visitor use to map and quantify the effects of transportation planning alternatives on visitors’ soundscape experiences. Examples of how these methods have been implemented in national parks are discussed.
Transient cavitation in high-quality factor resonators at high static pressures.
Authors: Gaitan D. Felipe , Pishchalnikov Yuri A. , Matula Thomas J. , Church Charles C. , Gutierrez Joel , Scott Corey , Holt R. Glynn , Crum Lawrence A.
Published: July 2011

Cavitation collapse can generate intense concentrations of energy, sufficient to erode even the hardest metals and to generate light emissions visible to the naked eye [sonoluminescence (SL)]. The phenomenon of “single bubble sonoluminescence” (SBSL) in which a single stable cavitation bubble radiates light flashes each acoustic cycle typically occurs near 0.1 MPa static pressures. Impulse Devices, Inc. has developed a new tool for the study of SL and cavitation: a high quality factor, spherical resonator capable of achieving acoustic cavitation at ambient pressures in excess of 30 MPa. This system generates bursts of violent inertial cavitation events lasting only a few milliseconds (hundreds of acoustic cycles). Cavitation observed in this system is characterized by flashes of light with intensities up to 1000 times brighter than SBSL flashes as well as spherical shock waves with amplitudes exceeding 100 MPa (1000 bars) at 1 cm from the cavitation center. Computer simulations indicate shock wave amplitudes near the collapsing bubble around 1–10 TPa (10–100 mbars) and liquid temperatures on the order of 5000 K, possibly causing the liquid to become opaque. The implications of these extreme conditions on SL emission will be discussed. [Work funded by Impulse Devices, Inc. ACPT Contract No. W9113M-07-C-0178.]
Comparison of single bubble collapse and cluster collapse in a high pressure vessel.
Authors: Matula Thomas , MacConnaghy Brian , Crum Lawrence , Gaitan Felipe
Published: July 2011

Details of the collapse of single bubbles and bubble clusters leading to the emission of a shock wave under high overpressures will be presented. Ultrahigh speed photography captures the events at various stages of bubble (or cluster) growth and collapse. Shock waves are observed millimeters from the collapse center, suggesting very violent conditions at the source. For example, shock waves emitted by single-bubble sonoluminescence can reach 3 mm/μs about 5 μm from the bubble center. With a cluster, we observe shock waves at this speed over 500 μm from the center. The strength of the collapse is estimated by measuring the emitted shock wave velocity from images taken with the ultrahigh speed imaging system. Cluster collapses can be much stronger than from single bubbles. Cluster collapse appears to be initiated by the collapse of outer bubbles.
Simultaneous measurements of shock waves, sonoluminescence flashes, and high-speed video of cavitation in high-quality factor resonators at high static pressures.
Authors: Pishchalnikov Yuri A. , Gaitan D. Felipe , Einert Mark S. , Holt R. Glynn , Church Charles C. , Crum Lawrence A.
Published: July 2011

Violent cavitation activity has been observed in water under hundreds of bars static pressure using Impulse Devices spherical resonators. To better understand the extreme conditions inside and in the immediate vicinity of the collapsing bubbles, we simultaneously recorded multi-frame shadowgraph images, acoustic pressure, and sonoluminescence (SL) flashes from the bubbles. Images of bubbles and shock waves were captured using a V710 Phantom high-speed camera (400 000 frames/s). The tip of a fiber-optic probe hydrophone was positioned in the field of view of the camera to correlate acoustic pressure with shadowgraph images of shock waves and bubble dynamics. SL flashes were collected with two photomultiplier tubes (PMTs, Hamamatsu, 1-ns rise time). The PMTs had identical ultraviolet filters but different sensitivities to extend the dynamic range from a single to thousands of photons. Typically a single bubble was spontaneously nucleated at the center of the sphere. After the first collapse, the bubble reemerged as a cluster of bubbles. The relationships among the static pressure, driving acoustic amplitude, the maximum bubble size, SL flashes, and shock wave amplitude will be discussed and compared with numerical results obtained using the hydrocode HYADES. [Funded by Impulse Devices, Inc. ACPT contract W9113M-07-C-0178.]
Complex demodulation of broadband cavitation noise.
Authors: Clark Pascal , Atlas Les , Kirsteins Ivars
Published: July 2011

Cavitation is a prominent source of ship noise resulting from the collapse of bubbles in the wake of rotating propeller blades. This same rotation also induces an audible rhythm, which is often modeled as a periodiclike modulator multiplying a broadband noise carrier signal. Conventional signal models restrict the modulator term to be non-negative and real-valued, accounting only for long-term energetic fluctuations in the time series data. However, recent empirical observations [Versluis et al., Science, 2000] and explanatory simulations [Ida, Phys. Rev. (2009)] reveal that interactions between multiple bubbles can lead to phase inversions in the form of negative pressure spikes. In this context we propose a more general complex-valued modulator that can account for energetic as well as phase-coherence patterns in the signal model. Through the use of synthetic signals and ship data examples, we will briefly discuss issues of detection and maximum-likelihood estimation related to the new complex signal model. For the purpose of fostering scientific understanding, however, our primary focus will be motivation for and estimation of the significance of possible complex modulation in both modeled and observed cavitation noise. [This research was supported by the Office of Naval Research.]
Physiology of the interaction between intensity and time at monaural and binaural stages.
Authors: Joris Philip X.
Published: July 2011

The two cues for azimuthal sound localization, interaural level differences (ILDs) and interaural time differences (ITDs), interact perceptually. According to the latency hypothesis, this interaction arises peripherally: Increases in intensity for the ear nearest to a sound source cause a decrease in response latency relative to the other ear. ILDs would thus shift the pattern of activation in an array of coincidence detectors that processes ITDs. Psychophysical studies have accumulated evidence against the latency hypothesis, but it has received support in several physiological studies that studied transient responses in a variety of binaural structures. We examined the basic premise of peripheral time-intensity trading in the auditory nerve with a coincidence analysis of responses to broadband noise. We found that changes in intensity cause small but systematic shifts in the ongoing timing of responses, generally but not always resulting in shorter delays between stimulus onset and neural response for increasing intensity. Overall, the results show that ongoing timing is remarkably invariant with intensity at the most peripheral neural level. The implication of temporal coding in monaural pathways for binaural ILD processing will be discussed in a wider context. [Supported by the Fund for Scientific Research—Flanders and Research Fund K.U. Leuven.]
Attentional tracking in real-room reverberation.
Authors: Makin Simon J. , Watkins Anthony J. , Raimond Andrew P.
Published: July 2011

A listener can attend to one talker in a mixture of sound sources, and a difference in bearing between “target” and interfering sources is thought to aid this “tracking.” Interaural cues are degraded by reverberation however, raising the question of what cues are actually used to track sources in rooms? Listeners can also use differences in voice characteristics, so this study asks how well cues arising from location compete with talker differences when tracking messages in real-room reverberation. Real room measurements of binaural room impulse responses (BRIRs) were used to spatialize the stimuli and listeners decided which of two simultaneous target words belonged in a target phrase played simultaneously with a “distracter” phrase. Location differences were in competition with talker differences so that listeners’ responses indicated which cue-type they were tracking. Further experiments used processed BRIRs to eliminate temporal cues. Location was dominant over talker difference in dichotic but not diotic conditions, and results with processed BRIRs indicated that this “binaural advantage” is almost entirely due to ILD. Furthermore, an analysis of spectral distances between BRIR channels revealed that the probability of location difference overriding talker difference correlates with the distance between ILD patterns but not with monaural spectral distances.
Getting the timing right: Meaningful variation in children's verbal response times.
Authors: Tice Marisa A.
Published: July 2011

Adults take turns in conversation with minimal gaps between speakers and almost no vocal overlap. Good conversational timing is a crucial skill all speakers must develop to enter into efficient and successful conversation. Children begin taking turns in conversation from infancy, supported heavily by their caregivers. Research on the acquisition of conversational timing, however, has been limited in scope, overlooking longitudinal data, parent-child interactions, and processing factors contributing to children’s response latencies. This study addresses these issues directly for question-answer pairs over the course of ages 1–3. Several factors were found to affect children’s response latencies in replying to their mothers’ questions, including interlocutor, age, question function, and answer complexity. In contrast to previous findings, children’s timing is, on average, nearly aligned with adult averages before the age of 4. Their timing is at adult ranges for certain early-mastered question functions and answer types. These effects interact with the child’s age, and the developmental trajectory hinges on both changes in the child’s response abilities and also in the kinds of questions the parent asks. Children’s timing and turn-taking abilities are more advanced than has been previously assumed, suggesting that children master turn-projection skills and pragmatically relevant factors early on.
Longitudinal formant analysis of Mandarin-learning children before 7 years of age.
Authors: Chen Li-mei
Published: July 2011

The present study is the seventh year of a longitudinal observation of vowel production in two Mandarin-learning children. In addition to gender differences, both subjects at 7 years of age experienced a slow growth stage after a rapid growth period in previous stages. Major findings are (1) girl subject used vowels with nasal endings more frequently than boy subject; (2) decrease of F1 F2 values is not so evident as in the previous stages in boy subject. As to girl subject, up to 7 years of age, no obvious change in formant values was found; (3) F1 values are more stable than F2 values in both subjects, especially in corner vowels. They appeared to acquire jaw movement sooner than tongue movement; (4) the earlier trend of shrinkage in F1-F2 vowel area was not found at this stage, and extension of vowel space was even found in both subjects; (5) there is no obvious trend of f0 decline in both subjects. Longitudinal data of vowel formant values from the same group of subjects provide important references for assessment and treatment of articulation disorders in children. [This investigation was supported through funds from National Science Council in Taiwan (NSC 96-2411-H-006 -023).]
The development of neutral tone in Mandarin-speaking children.
Authors: Yang Jie , Davis Barbara
Published: July 2011

Besides the four citation tones in Mandarin stressed syllables, neutral tone usually occurs in unstressed syllables. The fundamental frequency (F0) contour and height of neutral tone are determined by the preceding tones. Neutral tone was also considered to have lower intensity and shorter duration compared to citation tones [Cao (1986); Chao (1968)]. Li and Thompson [(1977)] suggested that neutral tone was not fully acquired by Mandarin-speaking children by age 2. However, the acoustic characteristics of neutral tone in the extended period of acquisition were not explored. The present study compared acoustic realizations of neutral tone in children’s production with adults. Eight 5-year-old and eight 8-year-old monolingual Mandarin-speaking children and young adults participated. Bisyllabic target words containing neutral tone in the second syllable were elicited by picture-naming tasks. F0, duration, and intensity of neutral tone syllables were measured. The ratios of these acoustic parameters between the first and second syllables were calculated. Results indicated that 5-year-old children started to produce F0 contour and height of neutral tone according to the preceding tone. But they still showed significant differences in the above-mentioned measures compared to 8-year-olds and adults.
Longitudinal changes of raw and normalized vowel space in children with cerebral palsy.
Authors: Lee Jimin , Weismer Gary , Hustad Katherine
Published: July 2011

The current study compares longitudinal changes of raw and normalized vowel space in 22 children with cerebral palsy in four different severity groups and over four time sampling points spanning a total of 18 months. 13 children had a clinical diagnosis of dysarthria and 9 children had CP, but no diagnosed speech disorders. The average chronological age of children at the first time sampling point was 50 months (SD= 9.8). Severity was operationally defined by orthographic transcription-based word intelligibility scores obtained from 176 listeners. Nearey’s normalization formula was employed to calculate normalized vowel space. Results showed both similarities and differences in longitudinal change patterns of raw and normalized vowel space in children with cerebral palsy. The difference between the two vowel space measures was most noticeable in children without speech disorders. Results will be discussed in terms of application and interpretation of normalization procedures in longitudinal vowel space data in pediatric population, comparison between raw and normalized vowel space measures, and comparison with previously reported data on developmental vowel space.
A cross-linguistic developmental study of vowel spectral movement patterns.
Authors: Chung Hyunju , Kong Eun Jong , Edwards Jan , Weismer Gary
Published: July 2011

Most studies of cross-linguistic differences in vowel production have focused on static formant values. However, Chung, et al. (in press) found systematic differences in spectral movement patterns between vowels produced by adult American English and Korean speakers. American English vowels showed greater magnitude and more consistent direction of movement, as compared to Korean vowels. The purpose of this study was to investigate the development pattern of these cross-linguistic differences. The first two formant frequency values of eight English vowels (/ɑ/, /e/, /ε/, /i/, /ɪ/, /o/, /u/, and /ʊ/) and five Greek and Korean vowels (/a/, /e/, /i/, /o/ and /u/) from word-initial fricative-vowel sequences produced by ten adults and twenty children (2-year-olds and 5-year-olds) were extracted. The duration of vowels was normalized to have seven different proportional time points. In order to minimize the effect coming from the preceding or following consonants, only the formant frequency values measured from the second time point to the vowel midpoint were used for the subsequent analysis. Results will be discussed with respect to the language-specificity in the vowel spectral movements and possible gestural differences across age groups. [Work supported by a Fulbright fellowship, NIDCD Grant No. 02932 and NSF Grant No. 0729140.]
Physiological constraints explain order of Mandarin tone acquisition in 3-year-old children.
Authors: Wong Puisan
Published: July 2011

Careful analyzes of childrens’ lexical tones revealed a more protracted developmental course than previously described. This study examined reasons for that late acquisition by performing acoustic analyzes on 289 monosyllabic Mandarin tones that were produced by 13 children and 4 adults and, subsequently, judged by 10 native listeners. Eight acoustic parameters that yielded strong correlations with the judges categorization of the tones were compared among adult correct productions, child correct productions, and child incorrect productions. Results revealed that childrens’ tone 1 (T1, high level) errors involved reduced f0 height and inability to sustain a level f0. Childrens’ tone 2 (T2, rising) errors reached minimum f0 later in the syllable and had either reduced rising or falling f0 slopes. Childrens’ tone 3 (T3, dipping) errors involved reduced syllable length, failing to reach a low f0, and having a much higher mean f0. Childrens’ incorrect tone 4 (T4, falling) productions had reduced negative f0 slopes. Even childrens’ correctly identified T1, T2, and T3 productions were not adultlike. The order of the four tones from the most to the least adultlike was T4, T2, T1, and T3, corresponding to the order of ease of speech motor control for the production of the tones.
A test of formant frequency analyzes with simulated child-like vowels.
Authors: Bunton Kate , Story Brad H.
Published: July 2011

Speech production by children is typically characterized by a fairly high fundamental frequency of phonation and a short vocal tract length that produces high formant frequencies. Together these two characteristics contribute to the difficulty of making accurate measurements of the formants because the vocal tract transfer function may be undersampled by the voice source harmonics. In addition, the close proximity of the low-numbered harmonics (including the fundamental) to a formant may lead to strong nonlinear interaction of the acoustic pressures in the vocal tract and the glottal airflow. The purpose of this study was to use standard spectrographic and LPC techniques, as well as new pitch-synchronous method, to measure formant frequencies of child-like vowels that have been simulated with a speech production model. Each vowel will be simulated with two different representations of the voice source: a glottal area model that allows for nonlinear source-tract interaction and a glottal flow model in which vocal tract characteristics cannot affect the source. The results of the analyzes will be compared to the actual formant frequencies calculated directly from the known vocal tract area functions used to generate the vowels. [Research supported by NIH R01-DC04789.]
Repetition of words from dense and sparse phonological neighborhoods in children with hearing loss and normal hearing.
Authors: VanDam Mark , Silbert Noah H. , Moeller Mary Pat
Published: July 2011

4 and 7 year-old children with normal and impaired hearing performed a listen-and-repeat task with words from dense and sparse phonological neighborhoods. Response accuracy was measured as a function of age, hearing loss, and neighborhood density. Accuracy was higher for older children, children with normal hearing, and for words from dense phonological neighborhoods. Age was evaluated cross-sectionally. Older children with normal hearing were consistently more accurate than younger children with normal hearing; children with hearing loss showed much smaller age-related differences. For children with normal hearing, accuracy for sparse neighborhoods was significantly higher for 7 year-olds than for 4 year-olds, but no such effect was observed for children with hearing loss; a similar pattern holds for words from dense neighborhoods. Relationships between accuracy, productive phonology (GFTA-II), expressive vocabulary (EVT-II), and degree of hearing loss (PTA dBHL) are also explored. These results suggest that phonological predictability, as measured by neighborhood density, is an important factor in the ability of children to perceive and reproduce words, interacting with both age and presence or absence of hearing loss. Absence of age-related performance improvement for children with hearing loss has theoretical implications for the role of auditory experience in development. [Work supported by NIH/NIDCD Grant Nos. R01DC006681 and P30DC04662.]
A nonword is a word is a word: Perceptual evidence for neighborhood density effects in preschool-aged children.
Authors: Woodley Melinda D.
Published: July 2011

Work with infants has suggested that children as young as 9 months are sensitive to phonotactic probability [Jusczyk et al. (1994)], yet there is little direct evidence for phonotactic facilitation effects in preschoolers [Munson et al. (2005)]. One possible explanation for this discrepancy is that as infants begin to assign meaning to lexical items, low level phonetic processing is essentially discontinued until competition among lexical items necessitates finer grained phonological representations [Werker and Stager (2000), among others]. However, another possible reason is methodological; work with toddlers has almost exclusively focused on production tasks. Adults clearly exhibit phonotactic facilitation effects in production [Vitevitch et al. (2004)], but any processing effects in children could be masked by noisiness in motor command implementation. The present study therefore examines the effects of phonotactic probability/neighborhood density on lexical access in preschoolers using a purely perceptual (“same/different”) task. Whereas adults exhibit a lexical competition effect for words and a phonotactic facilitation effect for nonwords in speech perception [Vitevitch and Luce (1999)], the present results demonstrate a significant lexical competition effect for both words and nonwords, suggesting that the lexical level is indeed the primary mode of processing for young children.
Bayesian histogram filter localizer performance in a multiple contact, continental shelf environment.
Authors: Sell Alexander W. , Culver R. Lee
Published: July 2011

Model-based recursive Bayesian state estimation provides a straight forward way of including a priori environmental knowledge in a localization framework. Previous work by Jemmott et al. demonstrates successful range and depth localization of an acoustic source using this method and data from a single hydrophone. However, that work utilized a relatively benign environment from the SWellEx 96 experiment in which only two source signals were present. This talk will extend the work of Jemmott et al. and discuss the performance of the localization scheme in a multiple contact, continental shelf environment. [Work supported by ONR Undersea Signal Processing.]
Cramer–Rao bounds for vector sensors.
Authors: Baggeroer Arthur B.
Published: July 2011

New formulations of the Cramer–Rao bounds for vector sensors are presented. They have the following advantages compared to previous expressions: (i) the formulation is simple and easy to evaluate involving the calculation of just three terms, (ii) arbitrary Green’s functions connecting source and observer can be used instead of plane waves, (iii) correlated noise vice white noise is easily introduced permitting the evaluation of the impact of interference, (iv) passive and active problems can be addressed, and (v) tomographic parameters can be introduced. In this presentation, these results are applied to source localization using towed arrays of vector sensors. Specific results include (i) the performance improvement of a vector array compared to a pressure array, (ii) comparison of vector arrays to twin line arrays, and (iii) the performance limits on a vector array to resolve right/left ambiguities and mitigate backlobe interference. [Work supported on ONR Code 321, Sonar Signal Processing.]
Sensitivity analysis of estimating bullet trajectories using ballistic shock wave measurements.
Authors: Frazier Wm. Garth
Published: July 2011

Estimation of the trajectory of supersonic projectiles using measurements of the shock cone is subject to several sources of measurement error as well as array geometry and miss distance. The microphone position measurement errors are especially important to consider in the case of a moving array. This investigation examines the sensitivity of the solution to these errors and parameters of the array geometry. Cramer–Rao bound analysis is performed in addition to Monte Carlo simulations using maximum likelihood estimation and a more computationally efficient alternative estimator. The results indicate that for several combinations of array geometry and microphone location error, solutions in practical applications can be of very limited value.
A deterministic filterbank compressive sensing model for bat biosonar.
Authors: Hague David A. , Buck John R.
Published: July 2011

The big brown bat (Eptesicus fuscus) uses FM echolocation calls to accurately estimate range and resolve closely spaced objects in clutter and noise. They resolve glints spaced down to 2 μs in time delay which surpasses traditional signal processing techniques. The matched filter for these calls maintains 10 μs resolution while the inverse filter (IF) achieves higher resolution at the cost of significantly degraded detection performance. Recent work by Fontaine and Peremans [J. Acoust. Soc. Am.(2009)] demonstrated that a sparse representation of bat echolocation calls coupled with a random FIR filter sensing method facilitates distinguishing closely spaced objects over realistic SNRs. Their work raises the intriguing question of whether sensing approaches structured more like the bat’s auditory system contain the necessary information for the hyper-resolution observed in behavioral tests. This research estimates sparse echo signatures using a gammatone filterbank closer to the bat auditory system. The filterbank outputs are decimated then processed with ℓ1 minimization. Simulations demonstrate that this model maintains higher resolution than the MF and significantly better detection performance than the IF for SNRs of 5–45 dB while downsampling the return signal by a factor of 6. [Work supported by ONR and the SMART Program.]
Extended Fourier for multi-component chirp analysis: Application to bat signals.
Authors: Assous Said , Linnett Laurie , Gunn David , Jackson Peter , Rees John , Lovell Mike
Published: July 2011

Much progress has been made recently for improving the time-frequency analysis. Typically, signals have frequencies that change with time. Even, in bio-acoustic, creatures such as bats and dolphins rely on time varying signals for echolocation and target detection. With the advent of pulse compression techniques in radar and sonar technologies, the need for time-frequency representations has become more important. The underlying basis of many of the techniques is the Fourier transform. In this paper, we present a technique, which relies on Fourier transform, exhibiting both greater resolution and conceptual simplicity. We have termed the technique Fourier extension analysis since it extends the use of Fourier analysis to signals with time varying components. Furthermore, we demonstrate how the analysis extends naturally to a time-frequency representation using the image processing Hough transform tool without the need for windowing, as it is the case for short time Fourier transform, for example, and we also discuss how the resolutions are obtainable with regard to separation of multi-component chirp signals. Examples will be presented for the analysis of some bat signals showing the capabilities of the developed technique compared to other methods in terms of resolution and cross term free advantages.
Analysis/synthesis of sonar echoes as impact sounds.
Authors: Gaumond Charles F. , Brock Derek , Wasylyshyn Christina , Hines Paul C. , Murphy Stefan
Published: July 2011

Active sonar performance is sometimes limited by clutter that generates an unacceptable false alarm rate (FAR). High FAR is overcome through the use of signal classification, which is treated here using a sequence of techniques that mimic human perception. The techniques are applied to a corpus of signals that were measured during the experiment Clutter 09, which took place on the Malta Plateau in the spring of 2009. First, techniques for foreground/background separation are presented using whitening and thresholding in a time-frequency representation adapted from computation techniques from acoustic scene analysis. The effects of thresholding are demonstrated with a few signals from the corpus. Modifications, suitable for the noisy sonar-echoes in the corpus, of the natural sound paradigm of Aramaki is presented [Aramaki, et al., Comp. Mus. Mod. Retr. CMMR 2009 (2009)]. Preliminary results of this representation are presented aurally. [Research funded by the Office of Naval Research.]
Narrow frequency analysis for periodic broadband noisy signals.
Authors: Ekimov Alexander
Published: July 2011

The Wigner–Ville transform was used twice for analysis of periodic broadband noisy signals. The first time use is for an extraction of informative part (part in future) from the signal when time window is sliding across a signal from a beginning to the end. Time window overlap N% is applied. This corresponds to N% time of existing window for a part of analyzed signal. The time window size is equal to the part duration time T1. That allows increasing the signal to noise ratio for this part within the window. Then the narrow Fourier filtration (which corresponds to the most informative part of the signal) is applied for the output of time window. Broadband signal becomes narrow band after that. Second time the Wigner–Ville approach is used to extract a periodicity in filtered signal. In this case second window was applied. This window size is at least two times more parts’ repetition time T2. Overlap is M%. This signal processing was successfully used for acoustic and electromagnetic signals of human motion due to footsteps and for underwater clicks of beaked whales in passive acoustic identification. [This work was supported by Army Armament Research, Development, and Engineering Center Contract No. W15QKN-09-C-0163.]
Three dimensional analyzes of scattering by pressure release sinusoidal surfaces. II. Results.
Authors: Welton Patrick J.
Published: July 2011

Theory from the preceding paper is compared with available experimental scattering measurements, and good agreement is found. The Fraunhofer and Fresnel phase approximations are examined, and limitations of validity are discussed. The interaction of the phase and beam approximations is examined as well as variations in the size of the scattering surface. Various slope approximations are compared. The significance of the Kirchhoff approximation and shadowing is explored within the limitations of geometrical acoustics.
A review of recent developments in underwater acoustic modeling.
Authors: Etter Paul C.
Published: July 2011

This is the fifth paper in a series of reviews presented at 8-year intervals starting in 1979 [J. Acoust. Soc. Am. 65, S42 (1979); 82, S102 (1987); 97, 3312 (1995); 114, 2430 (2003)]. All surveys cover basic acoustic models and sonar-performance models. Basic acoustic models include propagation, noise, and reverberation models. Propagation models are categorized according to ray theory, multipath expansion, normal mode, fast field, and parabolic approximation formulations; further distinctions are made between range-independent and range-dependent solutions. Noise models include ambient noise and beam-noise statistics models. Reverberation models include cell and point-scattering formulations. Sonar-performance models include active sonar models, model operating systems, and tactical decision aids. Active sonar models integrate basic acoustic models, signal processing models, and supporting databases into cohesive operating systems organized to solve the sonar equations. Model-operating systems provide a framework for the direct linkage of data-management software with computer-implemented codes of acoustic models. Tactical decision aids represent a form of engagement-level simulation that blend environmental and sonar-performance information with tactical rules. The current inventory of underwater acoustic models comprises 128 propagation models, 21 noise models, 28 reverberation models, and 35 sonar-performance models. Since 1979, approximately five models have been added to the inventory each year.
A computationally efficient multistatic reverberation algorithm.
Authors: Fromm David M.
Published: July 2011

The multistatic reverberation algorithm (MURAL), which supports trainer development, is presented. The algorithm can be used with any propagation model that produces range-sampled grids of transmission loss, travel time, launch, and grazing angles. The flexibility of MURAL with functions that calculate the propagation, scattering, and beam patterns is shown. A reverberation model should produce high-fidelity accurate results in real-time. In reality, the calculation almost always involves the trade-off between computational speed and accuracy. The operation of MURAL couples the algorithm controls to the requested resolution of the prediction with the goal of self-optimizing its performance for the requested resolution. Details are presented that address the technical issues of speed, accuracy, fidelity, and flexibility through several interrelated approaches including (1) the utilization of large amounts of memory available on today’s computers, 2) carefully tying the resolution of the look-up tables to the integration, and (3) reordering the nesting of the loops so that the pulse duration is applied after the receiver beamforming. [Work supported by the Office of Naval Research.]
Scattering in a Pekeris waveguide from a rough bottom using a two-way coupled mode approach.
Authors: Stotts Steven A. , Knobles David P. , Koch Robert A.
Published: July 2011

Scattering from a rough surface is described numerically with a two-way coupled-mode formalism that contains scattering effects to all orders and provides, in principle, an exact solution to the wave equation. Both scattered field and direct blast components are computed within the framework of the formalism. In contrast to finite elements, each modal component can be calculated separately. A comparison between the scattered component from the coupled mode and Born approximation solutions is presented for scattering from a rough bottom Pekeris waveguide. Total field time series are constructed, and the transition from direct blast to scattered field dominance is identified. For a Gaussian source pulse, the frequency band needed to resolve the scattered component is shown to be much less than is required to resolve the direct blast. Convergence tests to validate the accuracy of the solution are discussed. The importance of the nonlinear contributions to the scattering is identified. The usual method of time averaging the solution produces lower intensity levels than those obtained from the envelope of the time series.
Bottom reverberation modeling with limited bottom interaction information.
Authors: Zabal Xavier , Porter Michael
Published: July 2011

Frequently, the only available information on bottom interaction is the reflection loss as a function of grazing angle. Here we explore a method of incorporating this information into a normal mode code, such as KRAKEN, via the mode cycle distance. We compare this approach with the perturbation method used by KRAKEN with a full geoacoustic description of the bottom. Results are also compared to an exact solution using a full-bottom characterization. This approach using the cycle distance generalizes to full reverberation calculations, allowing one to predict the spatial and temporal structure of the active sonar reverberation field. The resulting model provides a small trade-off in accuracy but provides the reverberant field extremely rapidly.
Toward benchmarks of low frequency reverberation level in a Pekeris waveguide: Insight from analytical solutions.
Authors: Ainslie Michael A. , Ellis Dale D. , Harrison Chris H.
Published: July 2011

The requirement by modern navies to predict sonar performance in shallow water, whether for use in research, planning, or operations, led to an initiative for the validation of reverberation models in the form of two reverberation modeling Workshops at the University of Texas at Austin [J. S. Perkins and E. I. Thorsos, J. Acoust. Soc. Am. 126, 2208 (2009)]. The scenario considered here (Problem XI, from the first workshop) requires the computation of reverberation versus time in a Pekeris waveguide with Lambert scattering from the seabed. Simple analytical methods are presented that provide insight into the dominant propagation paths giving rise to the reverberation and hence establish regimes of validity for various computer models making different approximations or assumptions. Results from eigenray, normal mode, and hybrid continuum methods are compared with each other and with the analytical solutions. Numerical predictions are shown to overlap to within a few tenths of a decibel in regions where the different assumptions made by the various models are valid. These overlapping solutions are proposed as “benchmarks” in the sense of a baseline against which future model improvements can be assessed and quantified.
The modeling and analysis of the reverberation on the continental shelf off of New Jersey.
Authors: Choo Youngmin , Seong Woojae
Published: July 2011

As interest of operating sonar system in the littoral area increases, study of reverberation on a continental shelf is needed. In this study, an incoherent reverberation on a continental shelf was simulated using a 2-D propagation model based on ray theory with scattering strength formula based on various theories. Each scattering cross section was modified for application to von Karman roughness spectrum, which was observed during an experiment on the continental shelf off of New Jersey. Various reverberation patterns were shown according to each scattering cross section. By comparing the results from the model and experimental data, an adequate scattering strength was found for each source frequency, and the dominant mechanism of the reverberation on the continental shelf was identified for each time step. In case of the monostatic reverberation measurement, the source and receiver were located on the border between slopes. So both slopes affected the reverberation. In case of the bistatic reverberation, scattered signal from each slope affected the reverberation at different times. The characteristic of bistatic reverberation was different from that of monostatic reverberation. The effect of source-receiver separation on the reverberation of a continental shelf was studied through simulating monostatic and bistatic reverberations.