bluuebunny/crossref_metadata_2025 huggingface dataset:
Near- and far-field simulations of coherent backscattering from scatterers in finite sized aggregations
Authors: Mookerjee Adaleena , Dowling David R.
Published: November 2013

Classification of scatterers is a difficult but important step in active sonar applications. Active sonar signals in an ocean environment are scattered by surface roughness, and volume inhomogeneities in the bottom and water column. Fish schools may be important water-column clutter sources and, under some circumstances, may preferentially backscatter sound because of acoustic coherent backscattering enhancement (CBE). Here, the addition of in-phase scattered waves from propagation path pairs can readily explain a scattered intensity enhancement of a factor of two in the direction opposite to that of the incident wave. This presentation describes CBE simulations for finite sized aggregations of point scatterers using the Foldy (1945) equations that show much larger enhancements are possible in the far-field of the scattering aggregation. The simulations are validated in the near field with the theory from Akkermans et al. (1986), and with existing CBE optics and acoustics experiments from Wolf and Maret (1985) and Aubry et al. (2007). The dependence of the width of the CBE backscattered peak in the far-field is reported. Extension of these results to sonar pulse scattering from schools of fish is also very briefly discussed. [Work supported by the Office of Naval Research.]
Passive ranging in strongly range-dependent environments: Effects of mode coupling on the waveguide invariant
Authors: Sell Alexander W. , Culver R. Lee
Published: November 2013

Prior work has shown that the value of the shallow water waveguide invariant changes in range-dependent environments due to non-uniform phase and group speed along the propagation path caused by either a range-dependent bathymetry or sound speed profile. Much of the work on these scenarios has dealt with weak range-dependence and the effects of mode coupling were neglected. In certain situations when mode coupling occurs, energy from higher order, surface-reflected-bottom-reflected modes may be lost to lower order, surface-refracted-bottom-reflected modes. These lower order modes, which do not interact with the surface, are associated with waveguide invariant values that differ greatly from the standard shallow water approximation where the waveguide invariant equals one. This talk will examine a case from the 2007 CALOPS experiment where the adiabatic approximation for modal propagation is no longer valid and mode coupling appears to be important. Acoustical data and analysis will be presented to demonstrate the effect that mode coupling has on the waveguide invariant in strongly range-dependent environments, and methods for incorporating coupled modes into waveguide invariant estimates will be discussed. [This research was supported by the Applied Research Laboratory, at the Pennsylvania State University through the Eric Walker Graduate Assistantship Program.]
Architectural acoustics short course presentation material
Authors: Hoover K. Anthony
Published: November 2013

The Technical Committee on Architectural Acoustics (TCAA) is a Registered Provider in the American Institute of Architects (AIA) Continuing Education System (CES). The TCAA has developed a standardized introductory short course for architects, called “Architectural Acoustics.” An architect can earn one continuing education unit (CEU) by attending this short course, if it is presented by a qualified member of TCAA. The course covers topics in sound isolation, mechanical system noise control, finish treatments, and implementation of quality acoustical spaces. This paper will cover the course material in order to prepare and qualify potential presenters. In order to qualify as an authorized presenter for this AIA/CES short course, attendance at this special session and membership in TCAA are required.
Timing patterns of strobe groups for echolocating big brown bats performing a target detection task
Authors: Kloepper Laura N. , Simmons James A. , Gaudette Jason E. , Himmelwright Ryan , Robitzski Dan
Published: November 2013

While flying in dense clutter or close to objects, bats often produce “strobe groups,” pairs of pulses emitted at short pulse intervals followed by longer pulse intervals. Previous studies of free-flying bats demonstrate relatively consistent trends in strobe groups depending on the degree of clutter. To investigate strobe group production in stationary bats, three big brown bats were trained to perform a target detection task and their echolocation signals were analyzed. Variation in the number of pulses within strobe groups as well as strobe group characteristics varied substantially between individuals and experimental trials, yet when strobe groups were produced the time between pulses and strobe groups remained relatively stable. These data suggest that although bats demonstrate flexibility in the production and characteristics of strobe groups, the inherent timing of pulses within and across strobe groups is stable. These patterns may reflect precise timing adaptations in sound-producing motor circuits of individual bats.
Large eddy simulation of crackle noise in hot supersonic jets
Authors: Nichols Joseph W. , Lele Sanjiva K.
Published: November 2013

Crackle noise from heated, supersonic jets is investigated through high-fidelity large eddy simulation (LES). Simulations of a military-style nozzle reveal that N-shaped waves responsible for crackle noise emerge directly from the supersonic jet turbulence, and thus do not depend solely on nonlinear acoustic propagation effects. Conditional averaging using a backtracking algorithm furthermore reveals intermittent large-scale flow structures embedded in the jet turbulence as a likely source of the N-shaped waves. The skewness of pressure (Ffowcs Williams et al., 1975) and the skewness of the time derivative of pressure (Gee et al., 2007) are evaluated from full-field simulation data, and assessed as metrics of crackle. We test the hypothesis that the crackle level depends solely on the jet velocity (Ffowcs Williams et al., 1975) by comparing three simulations sharing the same geometry, but having different operating conditions so that the velocity and temperature are varied independently.
Ground and aerostat measurements of wind noise in the infrasonic range
Authors: Alberts W. C. Kirkpatrick , Waxler Roger , Reiff Christian , Sim Leng
Published: November 2013

Conventional deployment of infrasound sensors typically requires the sensors to be on the ground with extensive wind screens, e.g., porous hose or pipe arrays, in order to minimize wind induced noise on the sensor. Thus, flying an infrasound sensor on a balloon would seem ill-advised because of the inability to carry sufficient wind screens to mitigate the increased winds aloft. However, during an experiment designed to monitor short-range characteristics of low-frequency impulsive events, an infrasound sensor was placed aboard a tethered aerostat while the balloon flew to a maximum height of approximately 300 m. Comparisons between noise levels at the airborne sensor and at a nearby ground based sensor will be discussed. Noise levels aboard the aerostat are found to be similar to those on the ground.
Preliminary study of infrasonic attenuation and dispersion in the lower thermosphere, based on non-continuum fluid mechanics
Authors: Akintunde Akinjide , Petculescu Andi
Published: November 2013

A framework for predicting thermospheric attenuation and dispersion of infrasound between 80 and 160 km will be presented. The work is part of a pilot study whose goal is to complement the currently established models of thermospheric propagation, the standard being the Sutherland-Bass (SB) model [J. Acoust. Soc. Am. 115(3), 1012–1032 (2004)], which overestimates the observed attenuation noticeably. Based on the Navier-Stokes equation and its associated momentum and heat fluxes, the SB model treats the higher atmosphere as a continuum. However, for a given wavelength, the Knudsen (Kn) number increases rapidly in the thermosphere due to the high mean free path gradient. For Kn > 0.01, the continuum Navier-Stokes equations are no longer accurate. The present work shows how the predicted wavenumber changes when non-continuum approximations (e.g., the Burnett and 13-moment equations) are used. The ambient parameters and thermophysical properties are extracted from NIST, at the partial pressures of the main constituents (N2 and O2). The effects of rotational relaxation, gravity and tidal waves, neutral-charged and charged-charged particle interactions, UV heating/cooling rates, and other thermospheric processes will be addressed. [The work was funded by NSF-EPSCoR/Louisiana Board of Regents.]
Revisiting Hafter and De Maio: How precision of coding of interaural delay varies with both magnitude of interaural delay and center frequency
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: November 2013

Erv Hafter’s contributions span a broad range of topics fundamental to the understanding of monaural and binaural auditory perception. His publications and presentations are typified by historically important empirical, conceptual, and theoretical analyses. One issue he studied concerned how precision of neural coding of interaural time delay (ITD) varies with the magnitude of the delay and the spectral content of the stimulus. Such information remains central to contemporary quantitative models of binaural processing. Extending Erv’s efforts, we have developed a new way to measure precision of ITD-coding as a joint function of ITD-magnitude and center frequency. The novel twist entails transforming the classic NoSπ condition into (NoSπ)τ by imposing an ITD on the entire signal-plus-masker waveform. With that stimulus, uniform internal compensation of external ITDs would yield thresholds both independent of ITD and equal to those obtained under NoSπ. In accord with the results of Hafter and De Maio [J. Acoust. Soc. Am. 57, 181–187 (1975)], however, thresholds increased with ITD and did so more rapidly at 4 kHz than at 500 Hz. Our data were accounted for by assuming an internal, interaurally uncorrelated “processing noise,” the power of which increases exponentially with the magnitude of the internal, “matching,” delay.
Prediction and measurement of floor response due to walking
Authors: Murray Thomas M. , Davis Brad
Published: November 2013

The procedure for determine if a floor design will result in annoying vibrations due to walking in the American Institute of Steel Construction Design Guide 11 Floor Vibrations due to Human Activity is based on single degree of freedom response with a number of assumptions which reflect actual occupant conditions. Understanding the development of the procedure is necessary when comparing the results of field testing of problem floors. Development of the procedure, its accuracy when compared to a large data base of tested floors, and comments on appropriate testing protocols are presented.
Investigation on floor impact noise difference between Rhamen and wall-column constructions using vibration analysis
Authors: Hwang Dukyoung , Lee Sinyoeb , Park Junhong
Published: November 2013

Floor impact noise generation depends on the configuration of building structures. Especially, the Rhamen construction is known to radiate less than the wall-column construction. In this study, the sound radiation mechanisms between the two different structures are compared through experimentation using laboratory setup of the scaled model. The transfer of vibration energy from external impact source is calculated and compared with the measured results. Parameters affecting the radiated sound energy are determined and evaluated. The in and out-of phase vibrations of the building floors resulted in tonal sound radiation at two-closely located frequencies which resulted in modulated floor impact sound. This modulation increased the annoyance on the residents. Eventually, a design method to efficiently reduce the floor impact sound is proposed.
Dissipative effects in the response of an elastic medium to a localized force
Authors: Photiadis Douglas
Published: November 2013

The effect of dissipation on the real part of the admittance of an elastic half-space is typically thought to be unimportant if the loss factor of the elastic medium is small. However, dissipation induces losses in the near field of the source and, provided the size of the source is small enough, this phenomenon can be more important than elastic wave radiation. Such losses give rise to a fundamental limit in the quality factor of an oscillator attached to a substrate. Near field losses associated with strains in the elastic substrate can actually be larger than intrinsic losses in the oscillator itself if the internal friction of the substrate is larger than the internal friction of the oscillator. [This research was sponsored by the Office of Naval Research.]
A comparison of speech errors elicited by sentences and alternating repetitive tongue twisters
Authors: Shattuck-Hufnagel Stefanie , Bai Cathy , Tiede Mark , Katsikis Argyro , Pouplier Marianne , Goldstein Louis
Published: November 2013

Sound-level errors collected by ear from continuous communicative speech have been interpreted as mis-selections of planning elements, which are then produced fluently without residue of the original target (Lashley 1957, Fromkin 1972, Garrett 1975, Shattuck-Hufnagel 1982). In contrast, articulatory measures of tongue twister errors reveal gestural intrusions: target and intrusion elements are co-produced, sometimes resulting in a gestural error which is imperceptible to listeners (Pouplier 2003, Goldstein et al. 2007; see also Mowrey and MacKay 1970). Is this apparent difference due to structure and processing differences between the two utterance types, i.e., sentences (e.g., The top cop saw a cop top) vs alternating repetitive word lists (e.g., top cop top cop top cop) generally produced with quasi-periodic timing? Or, do articulatory measures simply capture the nature of sound-level errors more accurately? We elicited errors using both types of stimuli in the same experimental session; perceptual and acoustic analyses show that sentences provoke more apparent whole-segment substitutions (e.g., /tap/ for /kap/), while alternating repetitive lists provoke more errors with two onset bursts (e.g., /tkap/), resembling gestural intrusions. This suggests that there may be more than one mechanism underlying spoken errors, and that different materials may engage these mechanisms to different degrees.
An artificial neural network model for serial speech production and speech error simulation
Authors: Rusaw Erin
Published: November 2013

This paper presents serial speech gesture encoding and recall extension to the Neural Oscillator Model Speech Timing and Rhythm (NOMSTR), previously used to simulate prosodic and syllable timing (Rusaw 2010, 2013), and describes how it can be used to simulate speech errors and speech error patterns. This model uses NOMSTR to provide the phonological context vector which drives its serial recall, activating a series of gesture output nodes. Besides the prosodic context signal, the gesture output nodes have two other sources of input: (1) Nuclear gestures nodes provide excitatory input to the nodes required to produce the onset and coda gestures they share a syllable with; this mechanism is the ANN instantiation of the nucleus-centered syllable model. (2) Second, nuclear gesture nodes receive excitatory input from NOMSTR’s syllable-level thresholded node, which ties the timing of the gestures in a syllable to the time at which the syllable occurs in the phonological output. This extended version of NOMSTR is shown to able to simulate aspects of speech error behavior which other models have been unable to explain, such as C/V error (O-C/N) asymmetry, and error dependence (Rusaw and Cole 2009). [Work supported by NSF and NIH.]
The application of compressive sensing to underwater acoustic array processing and design
Authors: Rogers Jeffrey S. , Gaumond Charles F. , Edelmann Geoffrey F.
Published: November 2013

A brief overview of the application of compressive sensing to underwater acoustic array processing is given. Specific algorithms for estimating direction of arrival via L1 minimization are introduced. The Statistical Reduced Isometry Property (StRIP) is defined and used as a method to determine the ideal array designs for compressive beamforming. The tradeoff of using nested apertures and non-integer element spacing for improving StRIP over a broad range of frequencies is studied numerically. The array gain, which is a more directly useful performance metric, is also estimated using Monte Carlo methods. Compressive beamforming results from at-sea data taken on the Five Octave Research Array (FORA) will be presented. [Research funded by the Office of Naval Research.]
Near-field beamforming with augmentable non-uniform arrays for far-field interference suppression
Authors: Odom Jonathan , Krolik Jeffrey
Published: November 2013

This paper addresses the problem of adaptive near-field beamforming in the presence of many far-field interferers. Minimally redundant and, more generally, augmentable non-uniform arrays span larger array apertures and permit adaptive discrimination of more sources than sensors but require spatial-stationarity and increased snapshot support, which precludes their use for dynamic, near-field sources. In this paper, adaptive beamforming with augmentable non-uniform arrays is proposed which nulls relatively static far-field interference while enabling the detection of dynamic near-field sources. The use of an augmentable under-sampled array permits formation of a covariance matrix that can be used to implement reduced-rank dominant rejection of more interferers than sensors. Meanwhile, near-field beamforming in bearing and range is achieved using only the physical non-uniformly spaced sensor locations. An interference dominated environment is simulated to demonstrate the increase of array gain achieved over current techniques in the low snapshot support regime. [Work sponsored by ONR.]
Acoustic properties of oil/gas/sea water mixtures
Authors: Culver R. Lee
Published: November 2013

This paper presents an approach to calculating the acoustic properties, i.e., sound speed, and scattering cross-section, of oil, oil/gas, and oil/gas/sea water mixtures. The petroleum industry characterizes reservoir fluid in terms of the relationship between pressure, volume and temperature (PVT) of the oil utilizing the formation volume factor (FVF), which is defined as the ratio of the volume of oil at a pressure and temperature relative to a stock tank barrel (STB) at surface conditions. Another important oil reservoir parameter is the gas-oil ratio (GOR), which is the percent by volume of gas which is present in the oil at reservoir conditions (the gas is typically entirely dissolved—i.e., none is free—due to the great pressure). The reservoir fluid is typically under-saturated, meaning more gas could be dissolved in the oil, were it present. As the oil rises to the surface, the pressure and temperature drop. Once they drop below the bubble point, gas begins to come out of solution. Also, if fluids (oil and gas) are released into the ocean, sea water will become mixed in with the well fluids. The interest here is in the acoustic properties of oil only, oil/gas and oil/gas/sea water mixtures. The approach is to calculate the density and compressibility of the constituents and from them predict the aggregate acoustic properties using mixture theory.
Low scatterer density limit of effective medium theory
Authors: Dolder Craig N. , Lee Kevin M. , Wilson Preston S.
Published: November 2013

Often effective medium theories assume that there are multiple scatterers per wavelength; however, practical limits for these models can be far more flexible. Commander and Prosperetti's model for sound propagation in bubbly liquids assumes that “an averaging volume must contain many bubbles” but does not explicitly assume that there must be many bubbles per wavelength, though that assumption might be considered implicit in the use of effective medium theory. The results of Foldy's exact multiple scattering theory are compared to the effective medium theory for very low scatterer densities in order to determine the low scatterer limit for which the effective medium theory holds. This is compared with experimental results with low scatterer densities. It is shown that effective medium models for bubbly liquids hold even when there are as little as one scatterer per wavelength. [This work was supported by the Office of Naval Research.]
Ronald L. McKay, FASA: The Los Angeles years
Authors: Conant David A.
Published: November 2013

Ron McKay already had two very productive decades in various BBN field offices by the time we met in 1977, and was a high-level “generalist” with a growing portfolio of respected work in performing arts facilities. After 10 years together at BBN’s Los Angeles office, we established our own consulting practice, McKay Conant Brook inc, with an emphasis on spaces for large public assembly. This paper focuses on Ron’s contributions in the area of his special passion—performing arts—and various acknowledgments and awards leading to the prestigious AIA National Honor Award for Collaborative Achievement in 1999. His finest work was yet to come.
Deep-diving cetaceans and the Deepwater Horizon oil spill
Authors: Merkens Karlina , McDonald Mark , Baumann-Pickering Simone , Frasier Kaitlin , Wiggins Sean , John Hildebrand
Published: November 2013

The Gulf of Mexico is home to at least six species of deep-diving cetaceans, including beaked whales, sperm whales, and dwarf and pygmy sperm whales. These species are all found in the region that was impacted by the Deepwater Horizon oil spill. Using High-frequency Acoustic Recording Packages (HARPs), we monitored for their presence at three deep-water sites. From over two years of wideband (10 Hz—100 kHz) recordings, the detections of deep-diving cetacean sounds were related to environmental and anthropogenic factors using Generalized Additive Models to identify relevant features. The modeling showed that the significance of habitat parameters varies by species and site, although lunar illumination and sea surface height anomaly were significant for most species at all sites. The relationships between the acoustic presence of the cetaceans and their environment help provide an understanding of the ecology of these species as well as the potential impact of the oil spill on their habitat. This material is based upon work supported by BP and NOAA under Award Number 20105138. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the BP and/or any State or Federal Natural Resource Trustee.
Long-term bioacoustic monitoring for gauging animal populations: An approach involving flight calls of night migrating songbirds
Authors: Evans William
Published: November 2013

At times during the course of a year, the airspace over most locations in North America contains flight calls of night migrating songbirds. The calls typically have an audio frequency between 2 and 10 kHz and are 0.03-0.4 s in duration. Documenting such calls in a consistent manner enables temporal and quantitative calling patterns to be determined. Theoretically, such acoustic data gathered over time could be used as an index to population change as well as for documenting shifting migration routes. This presentation will discuss the development of a multi-sensor system designed to synchronously sample nocturnal flight calls of migrating songbirds across eastern North America. We will review the decisions involved with the system design that minimize non-target aspects of the soundscape and that help standardize monitoring over time. We will then illustrate the monitoring power of this application with flight call data from ten fall migrations at one monitoring station and two fall migrations from a transect of ten monitoring stations across eastern North America.
Wind dependence of shallow water ambient noise in a biologically rich temperate coastal area
Authors: Mathias Delphine , Gervaise Cedric , Di Iorio Lucia
Published: November 2013

The Iroise Marine Natural Park, created in 2007, is the first French natural marine park. This archipelago located in Western Brittany is a shallow water area that comprises 11 islands and hosts a rich variety of marine life, including seaweed fields, benthic organisms, endangered seals, and cetaceans. Three underwater autonomous recorders were moored at 10-m depth and sampled at 32 kHz from June 2011 to November 2011. Here we report on the dependency of shallow water ambient noise level on wind speed in a biologically rich environment. First we extract the ambient noise level in presence of transient sounds produced by benthic organisms by removing instantaneous sound pressure levels higher than a threshold computed using the kurtosis of the raw 10 sec time series. We then show that the ambient noise level allows to extract environmental information such as wind speed and biological rhythms, and that both are explaining 90% of its variance. Dependence of ambient noise and ocean noise level to wind speed at several frequencies are compared to reference work by Wenz (1962) and previous shallow water studies. Finally, we discuss how data assimilation coupling measured ambient noise and environmental parameters can help monitor marine ecosystems.
Laparoscopic high intensity focused ultrasound for the treatment of soft tissue
Authors: Sanghvi Narendra T. , Morris Adam
Published: November 2013

There is a growing demand to perform focal surgery, particularly for prostate and kidney tumors. RF and Cryo ablation are used for treatment of tumors; however, there are reported complications mainly skipping of cancer cells and bleeding. It has been shown that HIFU can provide acoustic hemostasis to overcome such complications. However, HIFU must compete with these modalities with improved treatment efficiency and the size of the applicator must fit in a 12 mm trocar/port used during the laparoscopic surgery. We modified the Sonatherm-600i applicator and transducer that generates a split beam HIFU at 4 MHz with a center element for imaging operating at 6.5 MHz. The transducer is integrated in a robotic probe that renders bi-plane images for tissue localization and ablation. Based on selected tissue ablation volume, treatment trajectory is generated by the computer to provide optimum thermal dose to result in complete coagulative necrosis. The treatment is conducted using continuous HIFU with an interlaced imaging for tissue change monitoring. The ablation efficiency of this device is @ 1 cc/min that is better than Cryo and RF ablation. Results will be presented from recent animal studies.
Pneumatic infrasound source: Expanded model development and tests
Authors: Muir Thomas , Slack Charles M. , Gorhum Justin D. , Hawkins Timothy M.
Published: November 2013

A model experiment discussed in a companion paper is expanded through the engineering development of a larger scale system to provide concept evaluation of portable infrasound generation, for calibration and tests of receiver array stations. This system utilizes an industrial compressor producing 350 cubic feet per minute of air at pressures up to 150 pounds per square inch, which is stored in two 500 gallon tanks. Air streams from each tank are released through two synchronized, rotating, 2 in. diameter ball valves, producing modulated pulse jets into the atmosphere, which then create infrasonic tone bursts. Measurements on the propagation and frequency response of infrasound so produced are compared and modeled with a view toward assessment of practical utility. [Work supported by Applied Research Laboratories, University of Texas at Austin.]
Best practices in measuring vowel merger
Authors: Nycz Jennifer , Hall-Lew Lauren
Published: November 2013

Vowel mergers are some of the most well-studied sound change phenomena, particularly in varieties of English. But although sociolinguists, dialectologists, and phoneticians are all interested in providing accurate and precise descriptions of an individual speaker's participation in a near-merger (or near-split), the methods for doing so vary widely, especially for researchers analyzing naturalistic corpora. In this paper, we consider four current methodological approaches to representing and assessing vowel distance and overlap: Euclidean distances between averages, Pillai-Bartlett trace (Hay et al., 2006), mixed effects regression modeling (Nycz 2013), and the spectral overlap assessment metric (Wassink 2006). We compare the advantages and disadvantages of each by applying all four methods to three separate data sets. These represent low vowel realizations by speakers from three different studies of English variation: one undergoing merger (COT and CAUGHT in San Francisco, California), one undergoing split, for the same contrast (COT and CAUGHT among Canadians in New York City), and one undergoing split, but for a different contrast (TRAP and BATH among Scots in England). By comparing the similarities and differences between the data sets themselves, as well as the differing analytic motivations for quantifying speaker-specific vowel overlap, we conclude with practical recommendations.
Speaking tongues are always braced
Authors: Gick Bryan , Allen Blake , Stavness Ian , Wilson Ian
Published: November 2013

Bracing the tongue against rigid vocal tract surfaces (i.e., teeth or palate) has been suggested to be important in facilitating certain kinds of tongue movements [Stone, J. Acoust. Soc. Am. 81, 2207–2218 (1990)]. However, previous studies have generally sought bracing in only a narrow range of phonetic contexts, resulting in a widespread view of bracing as an occasional state, peculiar to specific sounds or sound combinations. The present study uses electropalatography (EPG) as well as ultrasound imaging and electromagnetic articulometry (EMA) to describe tongue bracing in continuous speech passages, finding that the tongue is almost constantly braced against lateral surfaces during running speech. Analysis of archival data from the male and female speakers of American English in the KayPENTAX Palatometer Database (Model 4333) shows that they brace the tongue continuously, except during a small percentage of low vowels, and during a larger percentage of instances of /l/. Additional measures using all three devices, as well as biomechanical simulations using ArtiSynth (www.artisynth.org), provide further insight, indicating that the tongue also braces against the central palate and/or lower jaw, and that bracing points slide anteroposteriorly across speech sounds. These results suggest that bracing is a constant and necessary aspect of tongue motor control.
Interspeaker variability in relative tongue size and vowel production
Authors: Lammert Adam , Hagedorn Christina , Proctor Michael , Goldstein Louis , Narayanan Shrikanth
Published: November 2013

The tongue varies across speakers in terms of the proportion of the overall speech production apparatus that it occupies. Differences in tongue size have the potential to result in speaker-specific articulatory strategies for shaping the vocal tract area function and, in turn, individual patterns of vowel acoustics. The present study examines the interplay between relative tongue size and vowel production using real-time magnetic resonance imaging with synchronous audio. Two populations of native American English subjects are considered, one containing healthy adult speakers with no relevant pathologies, and another containing speakers who had undergone glossectomy as treatment for tongue cancer. All subjects were imaged in the midsagittal plane while reading phonetically balanced English sentences. The size of the tongue and the speech production apparatus were quantified from an overall average posture, and their ratio was correlated with the shape of the vowel space in terms of acoustics (e.g., formant frequencies), constrictions (i.e., location and degree of minimum constriction), and parameterized vocal tract cross-distance functions. Results indicate that relative tongue size can be used to explain and predict observable interspeaker differences in vowel production.
Using an exponential sine sweep to measure the vocal tract resonances
Authors: Delvaux Bertrand , Howard David
Published: November 2013

The vocal tract (VT) of a singer acts as a filter on the acoustic output from the vibrating vocal folds, enhancing several frequency bands whose peaks are called formants. The nature of these formants is characterized by the shape and dimensions of the VT and they are numbered with the first formant being the lowest in frequency. Perceptually, the first (F1) and second (F2) formants indicate the vowel being sung while the third (F3), fourth (F4) and fifth (F5) relate to the timbre or tone color of the output sound. It is therefore relevant to the understanding of the vocal organ to be able to measure the resonances of the tract with precision. Here we apply the exponential sine sweep method used in room acoustics to VT models and replicas. We use an exponential sine sweep as the source signal for the cavity and record its output. After convolving the output signal with the appropriate inverse filter, we can separate the linear impulse response of the tract from its harmonic distortions. This method is both applied on VT models of Chiba and Kajiyama and on MRI-based molded VTs.
A comparison of kinematic and acoustic approaches to measuring speech stability between speakers who do and do not stutter
Authors: Jackson Eric , Tiede Mark , Whalen Douglas H.
Published: November 2013

People who stutter have been found to exhibit reduced speech stability during fluent speech production relative to people who do not stutter. One index for quantifying stability that has been applied to stuttering and non-stuttering speakers is the spatiotemporal index (STI; Smith et al., 1995). STI measures the consistency of repeated speech movements aligned using linear normalization. Similar stability indices based on nonlinear methods for alignment have also been reported (e.g., Lucero et al., 1997). Both linear and nonlinear methods have been applied to kinematic signals in previous experiments. The present study tests the possibility that measures of stability based on acoustic signals can also be useful indicators of speech stability in adults who do and do not stutter (cf. Howell et al., 2009), as using audio recordings to calculate speech variability could provide an attractive alternative for speech-language pathologists and researchers who lack access to kinematic data. In addition, both kinematic and acoustic stability are assessed with respect to effects of linguistic complexity and social factors.
A discussion of possible measurement techniques for muddy sediments and of the related modeling challenges
Authors: Pierce Allan D. , Fayton Joseph O. , Siegmann William L.
Published: November 2013

Present paper draws on recent work of the late William Carey at Dodge Pond, CT, and on related modeling efforts at RPI. Carey affirmed that muddly sediments can have a substantial air bubble content. The water, solid particles (clay), and bubbles lead to a low sound speed that for low frequencies is explained by a modification of the Mallock-Wood formula. Independent measurements of mass density and sound speed should enable estimates of the fractional composition. The attenuation of sound in muddy sediments without bubbles is small, much smaller than of sandy sediments, and this is explained in terms of the card house model because of the very small size of the clay particles. The larger bubbles are randomly dispersed and have flattened shapes (also explained by the card-house model), and lead to scattering and reflection phenomena. Speculations are made as to whether inversion techniques can be devised to determine bubble shapes and size distributions. The small shear modulus of muddy segments has been tentatively explained in terms of electrostatic effects inherent to the card-house model, and this can possibly be measured by interface waves. Paper also suggests that penetrometer measurements, guided by theoretical modeling, may lead to useful inferences.
Issues in reverberation modeling
Authors: Tang Dajun
Published: November 2013

Reverberation usually consists of two-way propagation, or forward scatter, and a single backscatter. The scattering cross section is often employed to couple the two-way propagation to obtain approximate reverberation strength. Because this approach is inherently incoherent and heuristic in nature, certain limitations to its applicability need to be elucidated. In particular, unlike backscatter problems in half-space, reverberation in shallow water involves coherent incident fields at different wavenumbers. Starting with the fundamental definition of scattering T-matrix and through examples, this paper intends to address the following issues: (1) how to incorporate coherent component of reverberation into simulations, (2) how to rigorously relate time to range for given bandwidth, and (3) how to increase computation speed through proper smoothing. [Work supported by ONR.]
Seismic sources in seismo-acoustic propagation models
Authors: Collis Jon M. , Frank Scott D. , Metzler Adam M. , Odom Robert I.
Published: November 2013

An important generating mechanism for received underwater acoustic and seismic signals are buried or earth-bound sources. Most underwater acoustic studies involve purely compressional sources in the water column. The more complicated case of a coupled shear and compressional seismic source in the sediment has recently been implemented in an elastic parabolic equation solution [Frank et al., J. Acoust. Soc. Am. 133]. In this talk, generic seismic sources including those giving shear field contributions, are contrasted in normal mode and parabolic equation solutions. Scenarios considered are for an elastic-bottom Pekeris waveguide and a canonical Arctic propagation scenario with an elastic ice cover over the ocean and an elastic basement. For the Arctic case, the source is allowed in either the ice cover or in the elastic bottom. Solutions are benchmarked for purely compressional and shear seismic sources, and their relation to the seismic moment tensor is discussed. The ultimate goal of these solutions is to allow for seismic sources capable of representing generic geophysical events.
A scaled mapping approach for range-dependent seismo-acoustic propagation using the parabolic approximation
Authors: Metzler Adam M. , Collis Jon M. , Siegmann William L.
Published: November 2013

Parabolic equation solutions are used to accurately and efficiently model range-dependent propagation effects in ocean environments. There has been much recent interest in improving accuracy, particularly for sloping interfaces between fluid and underlying sediment layers. A translational mapping approach [Collins et al., J. Acoust. Soc. Am. 107 (2000)] applies a coordinate transformation in which a sloping bottom interface becomes horizontal and range dependence is mapped to the upper free surface. While accurate for small slopes, this approach introduces errors for variably sloping bathymetries since the range dependence is transformed to the surface. In this work, a scaled mapping is constructed that both transforms the sloping bottom interface to horizontal and also preserves the range-independent form of the free surface by distorting the waveguide in depth. The parabolic approximation is applied in the fully range-independent transformed domain, and the result is inverse transformed to obtain the solution in the initial range-dependent environment. Applications of this approach are given and benchmarked for seismo-acoustic propagation scenarios. [Work supported by ARL:IR&D.]
A comparison of acoustic and visual metrics of sperm whale longline depredation
Authors: Thode Aaron , Wild Lauren , Mathias Delphine , Straley Janice , Lunsford Chris
Published: November 2013

Annual federal stock assessment surveys for Alaskan sablefish also attempt to measure sperm whale depredation by quantifying visual evidence of depredation, including lip remains and damaged fish. An alternate passive acoustic method for quantifying depredation was investigated during the 2011 and 2012 survey hauls. A combination of machine-aided and human analysis counted the number of distinct “creak” sounds detected on autonomous recorders deployed during the survey, emphasizing sounds that are followed by a period of silence (“creak-pauses”), a possible indication of prey capture. These raw counts were then adjusted for variations in background noise levels between deployments. For most locations, the noise-adjusted counts of “creak-pauses” were highly correlated with survey counts of lip remains during both years (2012: r(10) = 0.89, p = 1e-3; 2011: r(39) = 0.72, p = 4e-3) and somewhat correlated with observed sablefish damage in 2011 [r(39) = 0.37, p = 0.03], but uncorrelated with other species depredation. The acoustic depredation count was anywhere from 3% to 80% higher than the visual counts, depending on the survey year and assumptions employed. The observed correlation breaks down when three or more whales are present. The results suggest that passive acoustics can provide upper bounds on the bias of survey depredation monitoring efforts for moderate depredation levels.
Dynamic encoding of sensory information in biomimetic sonar baffle
Authors: Pannala Mittu , Ramakrishnan Naren , Müller Rolf
Published: November 2013

The biosonar system of horseshoe bats stands through several dynamic features that could be related to an outstanding sensory performance. The outer ears (pinnae) of the animals, for example, can change their shapes in a non-rigid fashion and thereby produce qualitative beampattern alterations. Such changes can be reproduced qualitatively with a highly simplified biomimetic baffle prototype. Such a biomimetic prototype is a crucial platform for measuring large amounts of data on the time-variant device behavior that would be difficult to obtain from an animal in vivo. Here, such time-variant data were used to investigate the question whether a dynamic deforming baffle can enhance the encoding of sensory information. This was done based on estimates of the mutual information between beampatterns belonging to different deformation stages of the biomimetic baffle. To make this estimation problem tractable, the transfer functions associated with each direction of sound incidence were sorted into “alphabets” of a small number (X-Y) of discrete signal classes using spectral clustering algorithms. Mutual information estimates computed based on these signal classes indicated very low dependencies between the beampatterns even from moderately distant points in the deformation cycle and hence support the notion of dynamic sensory encoding.
Development and application of spot-poled membrane hydrophones for measurements of high intensity therapeutic ultrasound fields
Authors: Wilkens Volker , Sonntag Sven , Georg Olga V.
Published: November 2013

The reliable characterization of high intensity therapeutic ultrasound (HITU, HIFU) fields is important regarding the safe and effective clinical application of the modality. However, the required acoustic output measurements pose several metrological challenges. Extreme pressure amplitudes easily cause damage to the typical sensors, pressure waveforms comprise a large number of higher harmonics, and a small sensing element size is desirable due to the strong focusing. Membrane hydrophones are widely used as reference sensors due to their advantageous and predictable characteristics. However, they are usually considered to be rather fragile instruments possibly not well suited for HITU field characterization. A membrane hydrophone previously developed at PTB was tested by means of successive measurements at focus with increasing driving voltage, and the pressure range detectable without destruction of the hydrophone was determined. Second, a novel hydrophone design comprising additional protective layers and a backing was developed to increase the robustness against cavitation. After calibration, measurements were performed using an HITU transducer with working frequencies of 1.06 and 3.2 MHz. The examples show the favorable applicability for HITU field characterization. The maximum detectable rarefactional and compressional pressure amplitudes were 15 and 77 MPa, respectively, with a detection bandwidth of 50 MHz.
Non-invasive estimation of temperature using diagnostic ultrasound during high intensity focused ultrasound therapy
Authors: Bessonova Olga , Wilkens Volker
Published: November 2013

The use of HIFU for thermal ablation of human tissues requires safe real-time monitoring of the lesion formation during the treatment to avoid damage of the surrounding healthy tissues and to control temperature rise. Besides MR imaging, several methods have been proposed for temperature imaging using diagnostic ultrasound, and echoshift estimation (using speckle tracking) is the most promising technique. It is based on the thermal dependence of the ultrasound echo that accounts for two different physical phenomena: local change in speed of sound and thermal expansion of the propagating medium due to changes in temperature. In our experiments we have used two separate transducers: HIFU exposure was performed using a 1.06 MHz single element focusing transducer of 64 mm aperture and 63.2mm focal length; the ultrasound diagnostic probe of 11 MHz operated in B-mode for image guidance. The temperature measurements were performed in an agar-based tissue-mimicking phantom complying with the specification given in IEC60601-2-5. To verify the obtained results, the numerical modeling of the acoustic and temperature fields was carried out using KZK and Pennes Bioheat equations. The comparison of the results simulated and measured, as well as measured with thermocouples, shows a rather good coincidence.
Intracardiac myocardial elastography in humans in vivo during radio-frequency ablation
Authors: Grondin Julien , Wan Elaine , Gambhir Alok , Okrasinski Stanley , Garan Hasan , Konofagou Elisa E.
Published: November 2013

Intracardiac echocardiography (ICE) is commonly used during radio-frequency (RF) ablation procedures for procedural guidance. Besides its imaging function, ICE could be used to assess mechanical properties of the myocardium to improve the ablation outcome. The objective of this study was to demonstrate the feasibility of imaging myocardial strains in vivo within the same imaging plane as ICE at high temporal resolution. A 5.8-MHz center frequency ICE probe was used to image the heart of two humans with atrial arrhythmias in vivo before and after RF ablation at high frame rates (1200 Hz), and the channel data were acquired on a clinical ultrasound system. The RF signals were reconstructed on a 9cm depth and 90° field of view region and axial cumulative displacement estimation was performed using 1-D cross-correlation using a window size of 2.6 mm and 95% overlap. Cumulative axial strains were obtained from the displacements using a least-squares estimator with a kernel of 5.1 mm. Cumulative axial strains in the left atrium during systole were 23% and 18% in the two subjects before ablation, changing to 8% and 11% in the same location after ablation. Myocardial elastography could thus provide some quantitative methods for monitoring the generation of thermal lesions.