bluuebunny/crossref_metadata_2025 huggingface dataset:
Solution of the 3-D equations of elasticity in prolate spheroidal coordinates
Authors: Boisvert Jeffrey E. , Van Buren A. L.
Published: October 2013

The 3-D equations of elasticity in prolate spheroidal coordinates are solved using a Helmholtz decomposition for the displacement vector. The displacement vector is written in terms of a scalar potential (dependent on the dilatational wave number) and a vector potential (dependent on the shear wave number). These wave potentials are solutions, respectively, of the scalar and vector wave equations cast in prolate spheroidal coordinates. An eigenfunction expansion of spheroidal wave functions is employed to solve the scalar wave equation. The solution of the vector wave equation is facilitated using expansions of prolate spheroidal vector wave functions. These vector wave functions are constructed by applying certain vector differential operators to the scalar wave functions. The canonical problem of free vibration of a traction-free confocal elastic layer (shell) is considered. The shape of the prolate spheroid is defined by the major-axis length L and minor-axis length D. Since the sphere is a limiting form of the prolate spheroid, the analytical approach is validated by comparing the frequency spectra of a prolate spheroidal shell with L/D∼1 to those of a spherical shell using a 3-D solution in spherical coordinates. [Work supported by the NAVSEA Newport ILIR Program.]
Energy finite-element analysis of the NASA aluminum test-bed cylinder
Authors: Wang Aimin , Vlahopoulos Nickolas , Buehrle Ralph , Klos Jacob
Published: October 2013

A formulation was developed in the energy finite-element analysis (EFEA) for modeling the vibration of cylindrical structures with periodic axial and circumferential stiffeners. Appropriate power transfer coefficients are computed from the values of the propagation constants. The joint matrices of the EFEA formulation are computed based on the power transfer coefficients derived from periodic structure theory. EFEA analyses are performed for the NASA aluminum test-bed cylinder and simulations are compared to experiments. Excitation is applied on the test-bed cylinder by four shakers and the vibration is measured at 40 bays formed by axial and circumferential stiffeners. The EFEA results are compared successfully to test data between the 1/3 octave bands of 315 and 6300 Hz. [Work sponsored by NASA Langley Structural Acoustics Branch.]
Simulation of the propagation of the first antisymmetric Lamb mode in the audible range
Authors: Ribay Guillemette , Catheline Stefan , Cassereau Didier , Fink Mathias
Published: October 2013

When somebody knocks on a plate-shaped object, the first antisymmetric Lamb wave is created, propagates, and is reflected a lot before vanishing. It has been recently shown [Appl. Phys. Lett. 87, 204104 (2005)] that if the wave is recorded by an accelerometer, it is possible to deduce the knock position thanks to a cross-correlation technique. Now it is of interest to be able to simulate the wave field created in such experiments, for example in order to study the influence of various parameters, or possibly to try to replace the learning phase of this localization technique by a numerical prediction of the impulse responses. Therefore, in this talk, a finite difference code is presented, simulating the A0 wave in the frequency range excited by a knock on a plate, i.e., [0, 10 kHz]. It is based on a new wave equation of the flexural wave, which takes into account shear correction. Experiments on plates have been carried out to validate the simulation. It is shown that the spectrum of the experimental waves of this reverberant cavity is the same as the simulated one. [This work was financially supported by the TAICHI European project.]
Elastic and vibrational properties of a regular tensegrity structure
Authors: Smith Anthony R. , Piacsek Andrew A.
Published: October 2013

Invented by R. Buckminster Fuller and Kenneth Snelson between 1948 and 1961, tensegrity structures consist of stiff rods connected to flexible strings such that no rod is joined to any other rod. A prestressed tensegrity structure, in which all the strings are under tension, maintains a distinct shape, deforming slightly under a load. For the present study, tensegrity masts consisting of repeated layers of three-, four-, or five-rod patterns were constructed. With 15-cm rods, an eight-layer mast is 50 cm long and has a diameter of 20 cm. All masts exhibited a hysteretic nonlinear elastic response to applied stress along the major axis. Young’s modulus for the eight-layer mast ranged from 2500 to 5000 Pa at 8% strain. Increasing the tension in the strings by a factor of 2 resulted in a 14% increase in the Young’s modulus at small strains. Implications of this nonlinear behavior for wave propagation along the axis of a tensegrity mast is currently being investigated. Results will be shown for resonance frequencies as a function of drive amplitude. [Work supported by the Murdock Charitable Trust and Central Washington University.]
Spatial statistics of diffuse elastodynamic modes
Authors: Akolzin Alexei , Weaver Richard L.
Published: October 2013

Spatial statistics of the modes in an elastic body plays a useful role in predicting certain average elastodynamic responses of complex structures, such as transmitted power or nonlinear spectral energy redistribution. For single wave-speed fields, extensive evidence exists that high-frequency modes in the interior of a generic ray-chaotic body resemble a superposition of plane waves with random amplitudes and phases. This implies centered Gaussian statistics for the field amplitude and a specific form for the two-point correlation function. The former can also be linked to the imaginary part of the Green’s function averaged over a frequency band or over a characteristic ensemble of body realizations, which allows extension to the boundaries and inclusion of effects of finite body size. In the present study we analyze and compare theoretical expressions for a number of spatial statistics, such as intensity distribution, wave-type energy equipartition, and two-point correlation function, with numerical results for an ensemble of 2D plane-strain elastic bodies with rough boundaries.
Free vibrations of a polar elastic body
Authors: Altay Glay , Dokmeci M. Cengiz
Published: October 2013

This paper concerns certain features of the equations governing the time-harmonic free vibrations of a polar elastic body. The governing equations of micropolar elasticity are expressed in differential form; then, the uniqueness in their solutions is investigated. The conditions sufficient for the uniqueness are enumerated using the logarithmic convexity argument without any positive-definiteness assumptions of material elasticity. Applying a general principle of physics and modifying it through an involutory transformation, a unified variational principle is obtained for the free vibrations. The principle leads to all the governing equations of the free vibrations, as its Euler-Lagrange equations. The governing equations are alternatively expressed in terms of the operators related to the kinetic and potential energies of the body. The basic properties of vibrations are studied and a variational principle in Rayleigh’s quotient is given, and the high-frequency vibrations of a micropolar plate [cf., Altay and Dkmeci, Int. J. Solids Struct. (2006)] are likewise treated. [Work supported by TUBA.]
Progress towards a diffusion theory of wave energy transport in large irregular structures
Authors: Weaver Richard , Wolff Nicholas
Published: October 2013

We address the problem of constructing predictions for mean-square bandlimited displacement (‘‘energy’’) at points in a complex structure, and doing so with information gleaned from short-time cost-effective direct numerical simulations (DNS). Past work has shown that a DNS over short times subsequent to the action of a transient force allows good estimates of band-averaged admittances and therefore also of sensitivity to local energy density. (A further assumption of equipartition and no damping then permits estimates of response levels at infinite time.) We note that short-time DNSs also reveal a degree of transport and find that the transport operator observed to govern flow over short times may be iterated to predict energy distributions at later times. When carefully constructed, this iteration does a good job of predicting actual energies—at least for the special cases studied so far.
Context matters!—The influence of listening materials on L2 speakers’ performance of devoiced liquids in English
Authors: Chen Sally , Fon Janice
Published: October 2013

For previous L2 studies, the influence of context could be categorized either as the duration speakers live in an environment with their L2 as the official language or as the retaining effect after a certain amount of training. This study aims to investigate the variations on L2 learners’ production of English devoiced liquids with contexts of different degrees of directness provided. Sixteen subjects are divided into three groups. They are given an equal length of story (indirect context), wordlist (direct context), or music (control) in the listening task between two recordings of their production of a wordlist consisting of 14 monosyllabic English words containing a voiceless stop in the first position and a liquid in the second (e.g., play). Duration and ratio of the consonant clusters are measured and so is the voiceless portion of the clusters. Preliminary results showed that after the listening task, participants had a significantly longer duration for both cluster length and voiceless parts. Cluster duration of the two experimental groups was also lengthened. Furthermore, the wordlist group had their cluster/word and voiceless/cluster ratio closer to the native speakers in the second recording. Thus, practice effect, context effect, and directness effect were all supported.
Comprehension of envelope-only sentences by English-speaking adults and children and Mandarin-speaking adults
Authors: Nittrouer Susan , Packer Robert
Published: October 2013

Listeners comprehend sentences when only amplitude envelope information for a few bandlimited channels is available, but there is variability in their abilities to do so. This experiment asked whether the variability in listeners’ abilities to comprehend these signals is best explained by variability in magnitude of linguistic context effects, in auditory processing, or in sensitivity to structural organization at a global level. Stimuli were 30 four-word syntactically appropriate, semantically anomalous sentences, processed to preserve envelope information in 4 or 8 channels. Listeners were two groups of native English speakers (adults and 7-year-old children) and one group of native Mandarin speakers (adults) who were proficient enough in English to be graduate students at an American university. The sentences provided linguistic context that should affect comprehension equally for all these listeners, so that possible outcomes were (1) All three groups would perform similarly if abilities to use linguistic context best explained previously reported variability; (2) both adult groups would perform similarly and better than children if age-related differences in auditory processing best explained variability; and (3) English-speaking children and Mandarin-speaking adults would perform similarly and poorer than English-speaking adults if sensitivity to global structure best explained variability. Results matched possible outcome ♯3. [Work supported by NIDCD Grant No. DC-00633.]
Response to subthalamic deep brain stimulation on speech intelligibility in Parkinson’s disease
Authors: Wang Emily , Verhagen Metman Leo , Bakay Roy , Bernard Bryan
Published: October 2013

The study reports on intelligibility of reading and monologues produced by Parkinsonian patients who underwent unilateral subthalamic deep brain stimulation (STN DBS). Twenty right-handed individuals with advanced Parkinson’s disease (PD) and dysarthria underwent unilateral STN DBS. Ten were operated on the right hemisphere and ten on the left hemisphere. The side receiving STN DBS had more affected motor function. Speech was evaluated before surgery and three-to-six months after surgery with stimulator-off and with stimulator-on; all were off anti-Parkinsonian medication for 12 h before evaluation. Evaluators and subjects were blinded to the subjects stimulator status at the postsurgery evaluations. Nonspeech motor performance was assessed with UPDRS-III. Each subject read a standard passage and produced a monologue on a preselected topic. The readings and monologues were rated for intelligibility using UPDRS-III item 18. Sixteen student clinicians in speech pathology served as judges. Each speech sample was repeated three times. The reading and monologue samples were presented in two blocks. Within each block, the samples were randomly presented to each judge over headphones. Presentation and response collection were completed using a computer procedure written in Praat. The results are discussed with regard to speech and nonspeech motor response and to hemisphere-specific response on speech intelligibility.
Position variability in stop and fricative production
Authors: Lofqvist Anders
Published: October 2013

This study analyzed position variability in stop and fricative consonants, examining potential differences related to precision requirements. It has often been claimed that fricatives require more precision in their production than stops due to the management of airflow. However, there is very little, if any, empirical evidence for this claim which is mostly based on different developmental trends. Tongue movements were recorded using a magnetometer system. Measurements were made of tongue position at the onset of the consonant, defined in the acoustic signal. The results do not show any consistent pattern within or across subjects for stops and fricatives. Thus, there is not less position variability for fricatives than for stops. Taken together with results showing that the tongue movement during the closure is no less constrained for a fricative than for a stop, the present results thus indicate that the precision requirements for stops and fricatives do not differ. These results most likely reflect the fact that speech is an overlearned skill, so that any differences related to precision are very small, or nonexistent, in adults, and might only be seen in the early stages of speech development or second language learning. [Work supported by NIH.]
F0 and the voicing states of initial consonants in Mandarin
Authors: Zhang Chunling , Nearey Terrance M.
Published: October 2013

Studies have shown inconsistent F0 changes following the plain voiceless stops (F0PLAIN) compared to (1) voiced stops (F0VOICED) and (2) aspirated voiceless stops (F0ASPIRATE). Aerodynamic, laryngeal setting and auditory enhancement models of [±voice] have all been implicated in F0 variations [J. Kingston and R. L. Diehl, Language 70, 419–454 (1994)], but each explains only certain aspects of the prevocalic voicing effects on F0. Studies in English show that F0 of a vowel is simultaneously affected by multiple phonetic factors, such as voicing state, vowel identity, intonation, and place of articulation. Previous small-scale experiments in Mandarin also exhibit interactions of the phonetic distinctions on F0, but only certain aspects of the contextual variations of F0 have been examined. This study carries out a large-scale recording of Mandarin CV syllables in isolation, examining the interactive patterns of acoustic correlates of the voicing states of initial consonants. Preliminary results show dramatically different F0 changes from previous studies in Mandarin [C. X. Xu and Y. Xu, JIPA, 33, 165–181 (2003)] but show similar patterns to English, such that F0PLAIN is similar to F0VOICED (nasals), with F0ASPIRATE significantly higher. This study provides a better understanding of the cross-linguistic phonetic realization of voicing distinctions.
Active listening in passive-sonar soundscapes
Authors: Wakefield Gregory , Santoro Thomas
Published: October 2013

Listening tasks differ across a variety of dimensions. Tasks that are characteristic of competing channels are those in which command and control signals are delivered simultaneously. Such signals are typically highly uncertain, statistically independent, and nonredundant. Tasks that are characteristic of cooperative channels are those in which sources vary in some coordinated or collaborative fashion. Such signals are typically of much greater certainty, statistically correlated in several of their parameters, and highly redundant. We report on results from several types of cooperative-channel tasks in which listeners attend to targets in multiple-source soundscapes that resemble the passive sonar listening environment. Several levels of rendering are considered ranging from monaural to individualized binaural auditory displays with head motion. As the number of sources increases, performance degrades but at a slower rate than observed for competing channels. The fidelity of the binaural auditory display also affects performance, with greater performance gains being realized by more accurate realization of the listener’s head-related transfer functions. Finally, we introduce results concerning the perceptual asymmetry between source and head rotation and discuss the importance of head rotation in cooperative-channel tasks. [Research supported by a grant from the Office of Naval Research.]
Study on the human ability to aurally discriminate between target echoes and environmental clutter in recordings of incoherent broadband sonar
Authors: Allen Nancy , Hines Paul C. , Young Victor W. , Caldwell Douglas A.
Published: October 2013

Unacceptably high false-alarm rates due to the inability to discriminate between target echoes and environmental clutter are an issue for existing low-frequency active sonar systems operating in coastal environments. A research project at Defence R&D Canada—Atlantic is investigating the potential use of aural cues to tackle this challenge. One aspect of the project is to evaluate the human ability to aurally discriminate between target echoes and environmental clutter. The design and preliminary results from the study are presented here. Human subjects are presented with a series of sounds containing target echoes and clutter obtained from recordings of an incoherent broadband sonar experiment. The quantitative data collected in the study are the subjects’ decisions as to whether the echo heard was a target echo or clutter and their level of confidence associated with the decisions. Receiver-operating characteristic (ROC) analysis is used to produce a statistical model of the subjects’ performance. The study also includes a questionnaire: answers may prove useful in supporting the quantitative results and in providing a better understanding of the cues and decision techniques used by the subjects.
Automatic feature identification using multidimensional scaling data
Authors: Philips Scott , Atlas Les , Pitton James
Published: October 2013

Multidimensional scaling (MDS) listening experiments have long been used to better understand the perceptual cues human use when distinguishing between sounds in a given dataset. By collecting aural similarity measures between sound pairings, one can find the position of each sound in a D-dimensional perceptual space. The space allows the researcher to explore the perceptual attributes used to distinguish sounds. Typically, candidate signal features are correlated to each dimension to find which features accurately predict the signal positions in the perceptual space. Signal features generally exhibit varying degrees of correlation, with the optimal (highest correlated) feature declared to be the one used in perception. This method is not only ambiguous as to which feature (or combination of feature) is important to perception, but also is limited to previously defined signal processing features. Instead of optimizing over a limited set of features, one can optimize over a function which maps our signals to the perceptual MDS results. This approach allows one to find a transform of the data that better represents the complicated perceptual space. A number of solutions to the problem will be presented based on the results of an MDS experiment using active sonar echoes.
Modeling of the intensity channel impulse response for the East China Sea
Authors: Choi Jee Woong , Dahl Peter H.
Published: October 2013

Results of modeling the intensity channel impulse response in shallow and comparison with measurements are presented. The measurements were made in the East China Sea (depth 100 m, range ∼ 500 m) as part of the Asian Seas International Acoustics Experiment (ASIAEX). The intensity channel impulse response is obtained by incoherent summation of separate impulse response functions for each path (eigenray); the latter are modeled using ray and bistatic scattering methods. Measured sea surface spectral information and inverted seabed properties (from previously published works) are incorporated in the modeling. The modeled channel impulse response is convolved with representations of the CW (center frequency 8 and 16 kHz) or FM (frequency range 8–16 kHz) waveforms that were transmitted for comparison with observations. This talk will discuss (1) the influence of two-dimensional (out-of-plane) scattering including near-surface bubbles and the volume inhomogeneities in the sediment, on the intrapath time spread, and (2) the contribution of each arrival (up to the sixth path) to the channel impulse response. [Work supported by Office of Naval Research.]
Environmental effects on high-frequency propagation during the Makai experiment
Authors: Folegot Thomas , McDonald Vincent K. , Jesus Sergio M. , Badiey Mohsen , Hursky Paul , Porter Michael B.
Published: October 2013

The Makai experiment was conducted from 15 September to 2 October 2005 off Kauai Island to provide a comprehensive study of acoustic propagation in the 8–14-kHz band for diverse applications. Thermistor string measurements show how the interaction between the barotropic tides and the bathymetry generates a highly dynamic environment. Strong variability in the sound-speed profile has been observed, with diurnal and semidiurnal thermocline depth changes up to 50 m. Acoustic waves have been propagated at several ranges between two sources and receiver arrays, using fixed and drifted setup. The structure of the received impulse functions shows strong variability, although resolved arrivals are persistent.
M-ary frequency-shift-keying bit error rate analysis for a high-frequency underwater acoustic fading channel
Authors: Yang Wen-Bin , Yang T. C.
Published: October 2013

One of the prime advantages of M-ary frequency-shift-keying (MFSK) modulation is its ability to use an incoherent receiver. The incoherent receiver does not need precise frequency and phase estimates so that it can perform well, particularly in a significantly faded underwater acoustic communications channel. MFSK bit error rate (BER) performance using an incoherent receiver is determined by fading statistics of received signal amplitude. From our recent study in high-frequency underwater acoustic channel characterization, we found the fading statistics has a non-Rayleigh behavior and may be modeled as a K-distribution. In this paper, the MFSK BER is derived in terms of the parameters of the K-distribution. The theoretical BER is compared with measured BER of frequency-hopping (FH) FSK signaling data collected off the coast of New Jersey during the TREX04 experiment. The FH-FSK signal is a modified version of MFSK signals and was centered at 17 kHz with 4-kHz bandwidth. [Work supported by the Office of Naval Research.]
The digital preservation facility
Authors: Cohen Elizabeth
Published: October 2013

Critical listening should be an essential part of all archiving and restoration facilities quality control. We review the priorities and requirements for listening spaces ranging from the individual collector and small community archives to large-scale facilities. Examples discussed include the Library of Congress Culpepper facility, university libraries, and commercial facilities. Adapting listening rooms to the requirements of n-channel audio are discussed. Public recommendations of the Sound Preservation Board of the Library of Congress will be reviewed.
Acoustical design issues for library facility planners
Authors: Miyar Cristina L. , Hsieh Elaine Y. , Salter Charles M.
Published: October 2013

Acting under the provisions of the Library Services and Technology Act, the U.S. Institute of Museum and Library Services retained Charles M. Salter Associates, Inc. to provide a document explaining acoustical and audio/visual requirements for libraries to library planners, architects, and lay people. Acoustical design issues for libraries discussed on the website include site noise considerations, noise standards for each use space, room acoustics considerations, sound isolation between various use spaces, vibration control for mechanical equipment, and audio/visual system considerations. The completed document forms a part of the Libris Design library facility planning information system, which includes a website, , with recent information on facility planning topics and a database of recently constructed California public libraries.
Wireless technology and library acoustics
Authors: Markham Benjamin
Published: October 2013

The modern library cannot function without modern technology. Printers, copiers, wireless computers, and espresso machines all contribute to the soundscape of the typical municipal library (and many academic libraries, too). While some of these noise sources are stationary and can be isolated acoustically, wireless computing has transformed the acoustic experience for the typical library patron. Study carrels and desks used to define the boundaries of study and work areas in libraries, and architects could design spaces accordingly. With wireless technology, every space is a study space. This paper will discuss the implications of wireless technology on library acoustics. Measurement results at a variety of case study libraries will be presented.
Modern library design—architectural directions
Authors: Franco Isaac , Rosenberg Carl
Published: October 2013

The architectural practice of Moshe Safdie and Associates in Boston has been challenged by numerous clients recently to design major public libraries. The clients have stated an interest in making the library a major civic focal point and a place for community activities and identity. Moshe Safdie has responded to these challenges in Philadelphia, Vancouver, and Salt Lake City by designing buildings that encourage community interaction with large light-filled gathering spaces to support public congregating venues, shops and eateries, music recitals, meetings, electronic technologies, and even book club gatherings. This presentation will discuss the architectural context of contemporary library design. As a coda to the presentation, there will be a discussion about the acoustical implications of these new directions in civic library design.
Right whales—Social sound production
Authors: Parks Susan E. , Nowacek Douglas P. , Johnson Mark P. , Tyack Peter L.
Published: October 2013

Right whales use sound to mediate many social interactions. Examples include females producing screams to initiate the formation of surface active groups, adult males producing gunshot displays in agonistic contexts, and mothers producing contact calls when reuniting with their calves. We are just beginning to understand the more sophisticated abilities of right whales to utilize sound. Playback experiments demonstrate that right whales are capable of precise sound localization over long ranges and can remember these locations after the sound source ends. Further evidence suggests that individual recognition may play an important role in acoustic communication, from the simple examples from mothers and calves, to more complex evidence that some males preferentially approached playbacks of calls from specific females. Future research investigating the complexity of baleen whale sound use will include studies of individual recognition and the localization and spatial memory abilities of these whales. New technological developments are making it possible to answer these more complex questions and will reveal more details of how baleen whales to use sound to survive.
Imaging acoustic centers of the dolphin brain with positron emission tomography
Authors: Ridgway Sam , Houser Dorian , Carder Don , Hoh Carl
Published: October 2013

In human subjects, positron emission tomography (PET) has been used in diagnosis of disease, in studies of complex cognitive tasks, and in localizing areas of sensory activation, motor movement, and attention. Now, brain physiology of bottlenose dolphins, Tursiops truncatus, has been studied with PET. The dolphin brain is in the human size range but is more highly convoluted. The known acoustic centers of the dolphin brain are greatly enlarged compared with human brains. However, dolphins have a multi-tiered cortex with an extensive extra lobe, the paralimbic lobe, which does not occur in mammals or other animals outside the Order Cetacea. Because of its inaccessible location, there are no functional studies of the paralimbic cortex. PET offers an opportunity to study activity in this unique part of the dolphin brain during various stimulus conditions that may help to reveal functional aspects of the paralimbic cortex. For experimental scans, the dolphin was exposed to acoustic stimuli (tones or pulses) to reveal areas of relative brain metabolism after 18-F-FDG administration. These scans have revealed interesting features of the living dolphin brain including the paralimbic lobe as well as known acoustic areas in the cortex, midbrain, and acoustic nuclei.
Are manatees modifying their vocalizations to compensate for noise?
Authors: Miksis-Olds Jennifer L.
Published: October 2013

Elevated environmental noise levels have the potential to interfere with the acoustic communication system of manatees by masking signals containing biologically important information. Communication theory recognizes several ways a sender can modify its acoustic signal to compensate for noise. These include increasing the source level of a signal, its repetition, its duration, or shifting frequency outside of the noise band. To test whether manatees can modify their vocalizations to compensate for noise, vocalization usage and structure were examined in terms of vocalization rate, duration, frequency, and source level. Results imply that manatees do increase their vocalization energy expenditure, or vocalization effort, as a function of behavior and calf presence. Increases in vocalization rate, duration, and source level were most pronounced when calves were present and during behaviors whereby animals tended to be more dispersed, which may suggest a cohesion function. In conditions of elevated noise levels, manatees increased call duration during feeding and milling behaviors when calves were present, suggesting that ambient noise levels do have a detectable effect on manatee communication and that manatees modify their vocalizations as a function of noise.
Locating manatee position with an acoustic array
Authors: Buaka Muanke Paulin , Niezrecki Christopher
Published: October 2013

This paper presents the effort conducted in determining a manatee’s position by using acoustic methods. The time difference of arrival (TDOA) technique developed for the position location is used with the Hilbert envelope peak technique to estimate the time difference of arrival. The time differences obtained are converted into nonlinear hyperbolic equations which are solved using the least square method to perform the manatee localization. To improve the position location accuracy, with four hydrophones, six pairs of time delays are estimated and then combined (three by three) to give 20 calculated locations for each individual vocalization. To get a more accurate location, a statistical analysis test to remove the time delays combinations, which generate outliers, is applied on these 20 location results. Simulated results using the dSpace system for data acquisition and signal processing are presented for the case of an artificial tone signal. This method is applied to a variety of experimental data to test the systems performance.
Vessel damage mechanisms by ultrasound or shock wave pulses
Authors: Gracewski Sheryl M. , Miao Hongyu , Dalecki Diane
Published: October 2013

Edwin L. Carstensen has been one of the pioneers investigating not only the thresholds for bioeffects of ultrasound, but also determining mechanisms for these bioeffects, especially when air cavities are involved. Previous studies have demonstrated that hemorrhage or endothelial layer damage can occur when the blood vessels are exposed to lithotripter shock waves or to ultrasound in the presence of echo contrast agents. The presence of bubbles is often necessary for the damage to occur. Two main hypotheses describing the mechanism of vessel damage by acoustically excited microbubbles have been proposed. The vessel could be damaged by the high pressures and/or temperatures generated by the violent collapse of cavitation bubbles. Alternatively, the vessel could rupture upon bubble expansion. Here, a simple model is presented for vessel rupture upon bubble expansion and calculations are presented for parameters corresponding to two recently published experimental observations of vessel rupture and of endothelial cell damage to try to distinguish between these two mechanisms.
Nonviral gene transfer to murine liver in vivo is enhanced by exposure to high-amplitude, 1-MHz ultrasound with Optison■.
Authors: Brayman Andrew A. , Shen Zhenping , Chen Liping , Miao Carol
Published: October 2013

High-amplitude, 1-MHz ultrasound applied in pulse or burst mode at low duty factor, in conjunction with the injection of a mixture of gas-filled microspheres (Optison■) and plasmid, enhances nonviral gene transfer to surgically exposed murine liver in vivo. In this system, neither plasmid + ultrasound, nor plasmid + Optison produced significant gene expression relative to plasmid-only controls. The combination of plasmid + ultrasound + Optison produced a large enhancement of gene expression. The effect has a strong dependence on acoustic pressure. Together with the dependence of the effect on gas bodies, these results suggest that cavitation-induced permeability changes to hepatocytes are involved. Parametrization studies, the goal of which has been to further enhance gene transfer, will be discussed. At this writing, ultrasound treatments comprised by relatively brief pulses (20–40 cycles) at relatively high pulse repetition frequency (50 Hz) have produced nearly an order of magnitude greater gene expression than produced by tone bursts of several hundred cycles at low pulse repetition frequency (3 Hz) when plasmid and Optison are injected into the portal vein. [Project supported by NIH Grant R01 HL69049.]
Measurement of pressure produced at a solid surface by an acoustically driven cavitation bubble cloud
Authors: Ikeda Teiichiro , Yoshizawa Shin , Matsumoto Yoichiro , Bailey Michael R. , Crum Lawrence A. , Allen John S.
Published: October 2013

A cavitation bubble cloud typically acts as a strong acoustic scatterer; however, at certain frequencies and amplitudes waves transmitted by a cloud are amplified. A long-term goal is to break up kidney stones by using a two-frequency ultrasound forcing method with one frequency that generates the cloud followed by a lower second frequency that excites its violent collapse. The goal of this study is to determine the frequency and pressure amplitudes which produce the largest pressures as measured by a PVDF membrane on the stone surface. Reflection was also measured by a concave PVDF sensor placed 40 mm from the surface, and cloud sizes were determined by high-speed camera images. Transmission is quantified by the force. Reflection and transmission showed a reciprocal relation: peak in transmission corresponded to a minimum in reflection. The largest cloud observed created the largest reflection, whereas the smallest clouds created the largest transmitted signals. Forces generated by the small clouds were five times larger than the amplitude without a cloud. Thus, in using a two-frequency excitation combination, the pressures generated by the cloud cavitation might be optimized for lithotripsy applications. [Work supported in part by NIH DK43881 and NSBRI SMS00402.]
On the impact of vessel size on the threshold of bubble collapse
Authors: Sassaroli Elisabetta , Hynynen Kullervo
Published: October 2013

Most of the studies investigating the physical properties of ultrasound contrast agents have addressed situations in which the microbubbles are contained in vessels much larger than the bubble size. Since contrast agents are normally injected into blood vessels, the investigation of their behavior in a confined environment may reveal useful information for the optimization of diagnostic and therapeutic applications of ultrasound. A series of experiments involving an ultrasound contrast agent in different sized silica and polyester tubes ranging from 50 to 400 microns in internal radius is presented. It is shown that the threshold for bubble collapse, as recorded by broadband acoustic emission, is not only dependent on the applied pressure amplitude but also on the tube size with an increase for smaller vessels. These data are interpreted and rationalized on the basis of a simple physical model. These findings may have implications for the evaluation of the risk of inertial cavitation in blood vessels. [Work supported by NIH RO1-EB003268 and by the Brigham Radiology Research and Education grant.]
Broadband barrel-stave flextensional transducers
Authors: Jones Dennis F.
Published: October 2013

The last time I discussed underwater transduction technologies with Joe Blue was at the 125th Meeting of the Acoustical Society of America in May 1993. As we enjoyed lunch on the patio of a downtown Ottawa bistro under a sunny spring sky, the discussion touched on broadband transducers for naval applications. His ideas were insightful, motivating me to redesign and improve my original 1989 broadband barrel-stave flextensional transducer the following year. Over the last decade 30 experimental units were built at DRDC Atlantic, most of them used in marine mammal and coastal surveillance applications [D.F. Jones, J. Acoust. Soc. Am. 117, 2447 (2005); 118, 2038–2039 (2005)]. This paper will present electroacoustic measurements made at both the DRDC Atlantic Acoustic Calibration Barge on Bedford Basin near Halifax, Nova Scotia and the NAVSEA Seneca Lake Sonar Test Facility near Dresden in upstate New York. The performance parameters of interest include resonance frequencies, mechanical quality factors, transmitting voltage response versus water depth, and directivity patterns. [Work supported in part by the Office of Naval Research.]
Acoustic performance of sound-attenuating ducts utilizing spatially periodic area changes with absorbing material
Authors: Bliss Donald , Danilov Pavel
Published: October 2013

Sound propagation of one-dimensional waves through a duct with spatially periodic area changes has been studied theoretically and experimentally. The resulting wave behavior is similar to that observed for periodic structures, with Bloch waves, passbands, and stopbands. This configuration substantially reduces sound transmission from noise sources having harmonics that fall in the stop bands, while having little effect in passbands. The present study adapts this concept to configurations with dissipative sound-absorbing material. The periodically spaced regions of the duct with larger cross-sectional area are partially filled with porous material, so that the open cross-sectional area remains constant throughout the duct. The duct is analyzed as a quasi-one-dimensional system using an approach based on periodic structure theory. The porous material makes the propagation wave number in the porous/open subsections complex, thereby changing the nature of the stop- and passbands, and providing significant attenuation even in passbands. Results demonstrate that the best attenuation strategy may be to distribute the porous material in periodically spaced subregions rather than in either a single larger volume, or in a uniform distribution all along the duct, particularly if cancellation of discrete harmonics is desirable.
Synchronized-piezoelectric auto-oscillators, a classical analog laser
Authors: Weaver Richard , Lobkis Oleg
Published: October 2013

We report the behavior of two ultrasonic transducers, each part of an auto-oscillating Wein bridge, in contact with a high-Q elastic body. In particular, we compare the behavior of the one- and two-transducer cases. Each transducer oscillates erratically, and at its own frequency, when isolated and not in contact with the elastic body. When placed in contact with an elastic body, each transducer then stabilizes at a frequency close to the range of the original erratic oscillation, where it excites a ‘‘mode’’ (not necessarily a normal mode of the body) of the system. When both are in contact with the elastic body, a new mode is excited, and both transducers oscillate at the same frequency. They are locked to themselves and to each other by virtue of their mutual access to the same acoustic system, and the power output of the pair is, presumably, approximately 4 times as great as that of either transducer by itself.
Transmission effects of flexural shell vibration modes in sonic band-gap crystals made of hollow cylinders in air: A theoretical analysis
Authors: Kosevich Yuriy A. , Sánchez-Dehesa José , Goffaux Cecile
Published: October 2013

The transmission properties of periodic arrays of hollow cylinders in air are studied analytically and numerically using a finite-difference–time-domain method. Particularly, transmission spectra across slabs of a few layers of cylinders arranged in a square lattice will be reported. It is shown that n=2 and n=3 flexural shell vibration modes [A. Leissa, Vibrations of Shells (Acoustical Society of America, New York, 1993)] associated with the hollow cylinders play a fundamental role in the band-gap transmission properties of this two-dimensional sonic composite medium. The parameters of the hollow cylinders (thickness and elastic parameters of the material) are chosen in order to have the frequencies of the n=2 and n=3 flexural shell vibration modes inside, correspondingly, the first and third band gaps of the sonic crystal. In comparison with corresponding sonic crystal made of full cylinders, the transmission properties of this new composite medium present two main physical features: (i) huge transmission resonances with asymmetric Fano-type shape appear in the band gaps; and (ii) widening of the band gap widths occurs and increases with filling fraction of cylinders in the sonic crystal. Analytical expressions for the resonance frequencies and physical picture of both phenomena will be presented. [Work supported by MEC of Spain.]
Optimizing miniature thermoacoustic coolers
Authors: El-Gendy H. , Kwon Y. , Lyard L. , Symko O. G.
Published: October 2013

Because of limited sound intensity output from commercial drivers at midaudio and ultrasonic frequency ranges used in thermoacoustic coolers, it is important to optimize their performance. To achieve this, studies were conducted on heat transfer at the cold heat exchanger and at the hot heat exchanger. Measurements were taken on stray heat influx to the cooler by mechanisms of convection, conduction, radiation, and streaming, and from the driver. PIV studies show the contributions of streaming, both from the driver and other parts of the devices. A special 4-layer copper mesh heat exchanger was designed and tested to cope with heat pumped acoustically from the cold heat reservoir as well as the streaming from the piezoelectric driver. For typical sound levels of 155–160 dB achieved inside the resonator by commercial bimorph piezoelectric drivers, a cooling power density of 0.5 watts/cm2 was achieved with air at 1 atm. Pressurizing the working gas to 17 atm raises the cooling density. The choice of working gas provides a increase in power density. With the above optimizing approaches, a cooling power density of over 50 watts/cm2 appears feasible for the frequency range of 4 to 24 kHz. [Work supported by a grant from the ONR and the State of Utah.]
Cuing in auditory detection
Authors: Hafter E. R.
Published: October 2013

A traditional theory of auditory attention describes it metaphorically as the beam of an attentional searchlight. It underlies, for example, the logic of the auditory critical ratio, where subjects detect a tonal signal in a wideband masker, where the extent to which processing is restricted to a specific frequency-region is inferred through calculation of the critical ratio between signal level at threshold and the spectrum level of the masker. Values so found correlate well with results from other techniques such as restriction of the masker by notched noise and presentation of unexpected probe signals that are presumably attenuated by the skirts of the listening band. Lower performance in response to subjective uncertainty about the signal’s frequency has been modeled by assumptions of a wider attentional searchlight, i.e., listening band, an idea supported by alleviation of uncertainty effects by cues that inform the subject about where to listen. The plan here is to review experiments in which various kinds of cues have been used to focus attentional searchlights, including a discussion of the potential for use of this method for examining filters at higher levels of auditory analysis where the effective signal is an emergent property of the basic stimulus.
Multiple mechanisms of auditory attention
Authors: Sussman Elyse S.
Published: October 2013

Selective attention limits processing so we can handle the vast amount of information that we encounter daily. Actively selecting a subset of sensory information has been shown to bias response properties of neurons within sensory cortices, generally seen as an enhancement of the neural activity associated with the attended stimuli. This talk will present another type of attention effect on neural activity, affecting the representation of sequential sounds in memory. Event-related brain potentials were used to identify the timing of various cognitive processes, the subjects’ perception of the sounds, and to assess the stages at which attention interacted with sensory input in perception. In one study, attention modified the grouping and storage of sequential sounds, reflected by the absence or presence of specific ERP components. In another study neural representations were biased by stimulus-driven factors without attentional control. In a third study, attention increased accuracy for discriminating stimulus information but did not change the way the information was organized in auditory memory. These results indicate that there is more than one mechanism of auditory attention operating at different processing stages depending on the listeners task, and supports the view that attention interacts with stimulus-driven processes to facilitate behavioral goals. [Research supported by NIH.]