bluuebunny/crossref_metadata_2025 huggingface dataset:
Implications of the variety of bat echolocation sounds for understanding biosonar processing
Authors: Simmons James A. , Hoffmann-Kuhnt Matthias , Leong Tzi Ming , Hiryu Shizuko , Riquimaroux Hiroshi , Knowles Jeffrey M. , Moss Cynthia F.
Published: September 2012

The variety of echolocation sounds used by different species of bats have implications for target ranging. Signals recorded at individual sites reveal species stacked in different frequency bands, perhaps to avoid cross-interference. Search-stage signals include short single-harmonic or multi-harmonic tone-bursts, or very shallow FM bursts. These narrowband sounds have abrupt onsets to evoke phasic on-responses that register echo delay, but with limited acuity. Wider FM sweeps used for searching by other bats evoke on-responses at many more frequencies for better delay acuity. These sound types may signify foraging in the open, within broad spaces bounded relatively remotely by trees or the ground. Intervals between broadcasts are consistent with biosonar operating ranges set by the boundaries of the scene in relation to atmospheric attenuation. Most species make transitions to wider signal bandwidth during interception by increasing FM sweep-width or adding harmonics. Additionally, wideband, multi-harmonic FM sounds are used by species that frequently fly vegetation; they use harmonic processing to suppress surrounding clutter and perceive the path to the front. These observations suggest basic echo-delay processing to determine target range, with increasing bandwidth first to improve delay acuity and then to determine target shape. [Work supported by ONR and NSF.]
Dolphins use “packets” of broadband clicks during long range echolocation tasks
Authors: Finneran James J.
Published: September 2012

When echolocating, dolphins typically emit a single short duration, high-frequency, broadband “click,” then wait for the echo to return before emitting another click. However, previous studies have shown that dolphins and belugas performing long-range echolocation tasks may instead emit a burst, or “packet,” of several clicks, then wait for the packet of echoes to return before emitting another packet of clicks. The exact reasons for the use of packets, rather than individual clicks, is unknown. In this study, the use of packets by dolphins was examined by having trained bottlenose dolphins perform long-range echolocation tasks. The tasks featured the use of “phantom” echoes produced by capturing the dolphin’s outgoing echolocation clicks, convolving the clicks with the impulse response of a physical target to create an echo waveform, then broadcasting the delayed, scaled echo waveform back to the dolphin. Dolphins were trained to report the presence of phantom echoes or a change in phantom echoes. At ranges below 75 m, the dolphins rarely used packets of clicks. For ranges greater than 75 m, the likelihood of packet use was related to both target range and echo strength. [Work supported by the SSC Pacific Naval Innovative Science and Engineering (NISE) program.]
Environmentally neutral complex broadband biomimetic waveforms for active sonar
Authors: Dobbins Peter F.
Published: September 2012

There is an expanding requirement to reduce the impact of man-made sound, including active sonar transmissions, on marine mammals in the defence, offshore and other sectors. This is driven partly by increased public interest in these animals, but mainly by legislation such as the US Marine Mammal Protection Act, and similar regulatory and licensing requirements throughout the world. Typically, such requirements are met using monitoring by Marine Mammal Observers or Passive Acoustic Monitoring. Having detected animals within a specified range, some form of mitigating action such as shutting down the sound source is then necessary. However, in general it is difficult to ensure the absence of marine mammals before transmitting, so it is desirable to look for forms of sonar waveform that are potentially less harmful to marine life. One way this might be achieved is to use signals derived from natural sounds such as the vocalisations of the animals themselves. It might be expected that such sounds would appear more familiar, thus reducing possible abnormal behavioural impacts. This paper reviews the use of such waveforms and presents a preliminary estimate of their performance in practical sonar systems, along with an assessment of the potential impacts on marine life.
A generalized sinusoidal frequency modulated waveform for active sonar
Authors: Hague David A. , Buck John R.
Published: September 2012

Pulse-Compression or Frequency Modulated (FM) active sonar waveforms provide a significant improvement in range resolution and reverberation suppression over Continuous Wave (CW) waveforms. The Sinusoidal FM (SFM) waveform modulates its instantaneous frequency (IF) by a sinusoid to achieve high Doppler sensitivity while maintaining desirable reverberation suppression. This allows the SFM waveform to resolve target velocities much better than the Doppler tolerant Hyperbolic FM waveform. However, the SFM suffers from poor range resolution as the Auto-Correlation Function (ACF) contains many ambiguous peaks generated by the periodicity of the SFM’s IF. The periodic sidelobes in the ACF for the SFM signal are similar to those exhibited by periodic CW waveforms, which motivated the development of FM waveforms to improve range resolution. This suggests that modifying the SFM waveform to use an aperiodic modulating function should improve range resolution while preserving Doppler sensitivity. This talk presents an active sonar waveform where the IF function is itself an FM chirp waveform, and for which the SFM is a special case. This generalized sinusoidal FM waveform resolves target range and velocity with reverberation suppression comparable to other well-established FM waveforms. [Work supported by ONR and the SMART Program.]
The origins of longitudinal waves in piano strings
Authors: August Brandon , Etchenique Nikki , Moore Thomas R.
Published: September 2012

The importance of longitudinal waves in piano strings has been previously identified by several investigators. Recent experimental work has provided insight into the origin of these waves and their relationship to the transverse string motion. These measurements indicate that there are multiple regimes in which longitudinal waves are created through different processes.
Automatic transcription of monophonic piano music
Authors: Pishdadian Fatemeh , Nelson Jill K.
Published: September 2012

Automatic music transcription refers to the process of transforming an acoustic musical signal into a written symbolic representation, e.g. a score. This process consists of extracting the parameters of note events, for instance pitches, onset times, and durations, from a raw acoustic signal. We have developed a novel algorithm for transcription of monophonic piano music, which addresses the challenges of pitch and note sequence detection in two stages: (1) The K-Nearest Neighbor (KNN) classification method is employed to identify K pitch candidates, based on spectral information, for each note event. (2) The most likely note sequence is determined by running a best-first tree search over the note candidates based on both spectral information and note transition probability distributions. The proposed two-step approach provides the performance gain achieved by incorporating note transition probabilities while maintaining significantly lower computational complexity than existing support vector machine and hidden Markov model methods. The algorithm was evaluated on a database comprised of excerpts from Bach's inventions. By performing a low complexity tree search based on note transition information, we achieve approximately 10% improvement over using only spectral information, correctly classifying roughly 85% of the notes in the database.
Perception of musical and lexical tones by musicians and nonmusicians
Authors: Lee Chao-Yang , Lekich Allison
Published: September 2012

This study explores the relationship between musical and linguistic pitch perception. We asked whether the ability to identify musical tones is associated with the ability to identify lexical tones. English-speaking musicians and nonmusicians were asked to identify Taiwanese level tones produced by multiple speakers. Because pitch range varies across speakers and the tones were produced in isolation, participants had to estimate relative pitch height without cues typically available for speaker normalization. The musician participants were also asked to identify synthesized musical tones without a reference pitch. The results showed that both musicians and nonmusicians were able to identify Taiwanese tones above chance, but only for tones in the extremes of the speakers’ overall pitch range. Preliminary data from the musicians show that musical tone identification accuracy was low and not associated with accuracy in the Taiwanese tone task. Implications of these findings for the music-speech relationship are discussed.
A straightforward method toward efficient and precise impedance measurement for microperforation panels under flow conditions
Authors: Jing Xiaodong
Published: September 2012

This paper addresses the problem how to measure acoustic impedance of microperforation panels (MPPs) under flow conditions. Since 1960s, many different methods have been proposed to tackle this problem, mainly motivated by the aim of reducing noise emission from aeroengines, ventilators and other fluid machines. It has been found that the presence of flow favorably enhances the damping of MPPs due to the mechanism of sound-vortex interaction. This, however, leads to flow-dependent acoustic impedance whose determination is rather difficult. Despite considerable efforts over the past decades, there is still stringent need for developing efficient and precise impedance measurement method under flow conditions in order to fully explore the potentials of MPPs. Towards this goal, a straightforward method has been put forward to measure the acoustic impedance of an MPP lined in a flow duct (JASA, 124(1), 227-234). The basic principle is that the dominate axial wavenumber is extracted from the measured wall sound pressure by means of Prony method, thereby the unknown acoustic impedance is algebraically solved from the dispersion equation. In this paper, the straightforward method is further extended to incorporate the effects of flow boundary layer and higher-order acoustic modes that are essentially important for practical applications.
An edge-source integral equation for the calculation of scattering
Authors: Svensson U. Peter , Asheim Andreas
Published: September 2012

A new integral equation for the scattering from rigid, or pressure-release, convex polyhedra and disks is presented. It is based on edge diffraction as a complement to the geometrical acoustics components, and uses directional edge sources as unknowns in the frequency-domain integral equation. Comparisons with reference results show that the new method gives correct results down to 0 Hz in spite of being a geometrically based method [Asheim & Svensson, Report TW610, KU Leuven, Dept. of Computer Science, 2012]. The two-dimensional unknowns are solved for all edges, straight or curved, of the scattering object, but this reduces to a one-dimensional unknown for certain geometries such as axisymmetric scattering from a circular thin disk, or plane-wave incidence onto a polygonal cylinder. The general integral equation can be solved with the regular Nyström technique, iteratively or by direct inversion. The scattered field is computed in a post-processing stage, and is added to the geometrical acoustics and first-order diffraction components, which are computed separately. The formulations for non-convex external, as well as internal, geometries are laid out, and time-domain versions of the integral equation are linked to previously published work on edge diffraction impulse responses.
A fast wave-based hybrid method for interactive acoustic simulation in large and complex environments
Authors: Xiao Tian
Published: September 2012

Modern acoustic applications require fast and accurate simulation in large and complex environments. Current methods are rather limited to very simple environments or not able to perform fast interactive simulations. Our objective is to develop an innovative and practical method to perform real-time or near real-time accurate interactive simulation in large and complex environments, such as urban environments up to one kilometer. A new method, the embedded hybrid method using immersed boundary within k-space PSTD has been proposed and developed to achieve the objective. Its performance, accuracy, parallel hardware acceleration, and capabilities to handle all kinds of environmental complexities have been rigorously validated and verified by a number of examples. It shows that with the utilization of modern many-core GPUs, the method can perform real-time or near real-time accurate interactive simulation in large environments of hundreds to thousands of meters with all kinds of complexities including (1) inhomogeneous and absorptive medium, (2) curved and arbitrarily-shaped objects, (3) and moving sources, receivers, and objects, and time-varying medium.
Adaptive rectangular decomposition: A spectral, domain-decomposition approach for fast wave solution on complex scenes
Authors: Raghuvanshi Nikunj , Mehra Ravish , Manocha Dinesh , Lin Ming C.
Published: September 2012

Computational wave propagation is increasingly becoming a practical tool for acoustic prediction in indoor and outdoor spaces, with applications ranging from noise control to architectural acoustics. We discuss Adaptive Rectangular Decomposition (ARD), that decomposes a complex 3D domain into a set of disjoint rectangular partitions. Assuming spatially-invariant speed of sound, spectral basis functions are derived from the analytic solution and used to time-step the field with high spatio-temporal accuracy within each partition. This allows close-to-Nyquist numerical grids, with as low as 3 points per wavelength, resulting in large performance gains of ten to hundred times compared to the Finite-Difference Time-Domain method. The coarser simulation grid also allows much larger computational domains. ARD employs finite-difference interface operators to transfer waves between adjoining rectangular partitions. We show that efficient, spatially-compact interface operators can be designed to ensure low numerical errors. Numerical solutions obtained with ARD are compared to analytical solutions on simple geometries and good agreement is observed.
Real-time sound propagation and noise modeling in outdoor environments using Equivalent Source Formulation
Authors: Mehra Ravish , Manocha Dinesh , Antani Lakulish , Raghuvanshi Nikunj
Published: September 2012

We address the problem of wave-based sound propagation in outdoor and urban environments. The goal is to accurately simulate acoustic effects, including interference, diffraction, scattering, and higher-order wave effects in large outdoor scenes. We give an overview of a precomputed wave-based solver that is based on equivalent source method and is mainly applicable to large, open scenes [Mehra et al. 2012]. As part of a preprocessing step, it computes a per-object transfer function that models the scattering behavior of each object, and handles pair-wise acoustic coupling between objects using inter-object transfer functions. The runtime component involves fast summation over all outgoing equivalent sources for all objects at the listener location. We highlight its runtime performance and memory efficiency and use it for noise modeling and prediction in outdoor scenes spanning a few hundreds of meters. The sound field is computed in three dimensions, modeling frequency-dependent propagation above ceilings, around buildings and corners, and high-order interactions.
Coupling of parabolic equation method with the scattering of sound
Authors: Parakkal Santosh , Wilson D. Keith , Vecherin Sergey N.
Published: September 2012

The problem of sound scattering by an infinitely long penetrable and impenetrable cylinder suspended over a realistic impedance ground is investigated. The analytical approach using the image source method in the scattering of sound involves expressing the total sound field at any receiver point (over a locally reacting ground) as the sum total of the direct field, the ground reflection from the source, scattered field by the actual cylinder and finally by its image. The exact solutions can then be expressed as an infinite series, containing Bessel and Hankel functions of increasing order. The coefficients of the scattered field are determined by matching the desired boundary condition (for a rigid circular cylinder, for example, the normal component of velocity is zero on the boundary). Although the preceding approach is commonly used in theoretical treatments of sound scattering, to the best of our knowledge this is the first time it has been attempted numerically with coupling to the Parabolic Equation (PE) method. Presented is a Two-dimensional case of sound scattering of PE generated acoustic field by an impenetrable (soft or rigid) and penetrable cylindrical obstacle over a finite impedance ground in a non-refractive atmosphere.
Observations with grazing and vertical incidence methods of ground impedance estimation
Authors: White Michael J. , Swenson George W. , Borth Jeffrey D.
Published: September 2012

At locations near a ground surface of interest, the ground impedance may be evaluated using a loudspeaker suitably disposed to broadcast toward both the ground and two vertically-separated microphones. By evaluating the complex gain ratio between the pair for a single tone, the usual approximation to the Green function for the monopole field above a locally-reacting ground can be inverted to find the surface impedance. This inversion is somewhat sensitive to noise, but it can also be found to vary according to the placement of microphones and speaker, apart from speaker directivity. Recently the method of Soh et al. [Soh et al. JASA 128:5 EL286 2010] was proposed for measuring ground impedance some distance from the source. Because the method relies more directly on the boundary condition at the ground, it may offer some benefit for use at shorter distances as well. We discuss the comparisons between measurements interpreted by both techniques, consider noise entering the estimation process and placement effects.
Acoustical design of Muriel Kauffman Theatre at the Kauffman Center for the Performing Arts
Authors: Komoda Motoo , Kallas Kayo , Beckmann Daniel , Toyota Yasuhisa
Published: September 2012

Muriel Kauffman Theatre, the horseshoe-style proscenium theater in the Kauffman Center for the Performing Arts in Kansas City, Missouri, opened in September, 2011. The 1800-seat theater was designed by the architect Moshe Safdie, and serves as the principal residence of both the Kansas City Ballet, and the Lyric Opera of Kansas City. Since ballet and opera performance were programmed as the primary use, the primary focus of the room acoustical design was to provide good natural acoustics for singers on the stage, and for the orchestra in the pit. This was achieved through careful study on the shape of the room. The walls surrounding the stage and proscenium, and the configuration of the ceiling were among the primary aspects of the room shape which were studied, as well as flexible room acoustics for programs with using amplified sound, such as pop music and spoken-word programs. The acoustical design and characteristics of the Muriel Kauffman Theatre are reported.
Bio-sonar signal processing
Authors: DeFerrari Harry A. , Wylie Jennifer
Published: September 2012

An ideal sonar for biological observations in the ocean should employ very long signals for Doppler resolution, wide bandwidth for time resolution and pulse compression properties for gain in order to reduce sound pressure levels to mitigate marine mammal concerns. Signal spread in time and Doppler (leakage) must also be eliminated so that direct arrival and reverberation signals do not leak and swamp bio-signal returns when operation in a continuous transmit and receive mode. Orthogonal codes would help multi-static applications. Here two types of signals and processing are presented and analyzed; 1) M-sequences with matched filter processing and 2) Inverted binary sequence with matched- inverse processing. Ambiguity diagrams of conventional active sonar signals are compared with the two candidate signals. Then the two methods are compared by numerical simulation for propagation in shallow channels with zero Doppler returns and moving bio-scatterers. It is shown that for realistic conditions leakage from direct and zero Doppler reverberation can be eliminated not just reduced. Limits on temporal coherence times of shallow water propagations channels are discussed. These approaches improve Figure of Merit of conventional active sonar by 10 to 15 dB and displays in the time Doppler plane simplify the interpretation of clutter.
Analysis of biosonar beamwidth with spherical harmonics power spectra
Authors: Motamedi Mohammad , Xu Qiuping , Mio Washington , Mueller Rolf
Published: September 2012

Ultrasound emission and reception in bats are characterized by beampatterns that can be predicted from digital models of the geometries of noseleaf and pinna structures numerically. One obvious way in which beampatterns can differ across species is in the overall width (angular extent) of the beams. But since biosonar beams also vary in many other ways such as in their orientation and their shape, quantifying overall beamwidth poses a challenge. Here, the power spectrum of a beam decomposition based on spherical harmonics has been used to obtain a quantitative measure of beamwidth. Due to the reciprocity between transform domains, narrower beams correspond to spectra with a higher bandwidth and vice versa. Using power spectral magnitudes, it has been possible to classify emission and reception beampatterns as well as beampatterns from different taxonomic bat groups across 176 noseleaf and 185 pinna samples representing 106 species. Furthermore, when the power spectra of the actual biosonar beams were replaced with those of fitted single heat functions, classification performance suffered little. Since the heat kernel approximations did not differ in any property other than beamwidth, this demonstrates that beamwidth alone is a discriminating factor between bat taxonomic groups as well as emission and reception.
Examining the effects of propagation on perceptual features used for automatic aural classification
Authors: Binder Carolyn M. , Hines Paul C. , Pecknold Sean P. , Scrutton Jeff
Published: September 2012

A prototype aural classifier has been developed at Defence R&D Canada that uses perceptual signal features which model the features employed by the human auditory system. Previous effort has shown the classifier reduced false alarm rates and successfully discriminated cetacean vocalizations from several species. The current paper investigates the robustness of the aural features against propagation effects for two of those species - the bowhead and humpback whales. This is achieved by comparing the classification results of the original vocalizations to classification results obtained after the vocalizations were re-transmitted underwater over ranges of 2 to 10 km. To gain additional insight into the propagation effects, synthetic bowhead and humpback vocalizations, with features similar to the most important aural features for classification of bowhead and humpback vocalizations, were also transmitted. In this paper, the classifier performance on both real and synthesized vocalizations are compared before and after propagation, to quantify the effect of propagation on the features used in the aural classifier.
Propagation modeling techniques for marine mammal management studies
Authors: Küsel Elizabeth T. , Siderius Martin , Schecklman Scott
Published: September 2012

Acoustic propagation modeling techniques are often used to estimate the impact of anthropogenic sound sources on the marine environment, and to estimate population density and detection ranges of marine mammals from their vocalizations. Sophisticated propagation models can be used to accurately calculate acoustic transmission loss as a function of range and depth. This is often done along a number of uniformly spaced radials surrounding a sound source and results are interpolated to each simulated animal location. Computational time, detailed input parameters, and interpolation over complex bathymetry can be a hindrance to efficient and accurate results. This work investigates the impact of using simple propagation modeling that avoids interpolation between radials. Differences will be compared between direct and interpolated values as well as between coherent and incoherent transmission loss solutions. The accuracy and efficiency of the different approaches are evaluated by comparing the number of animals that would be taken by the sound field, which are associated with randomized animal locations in Monte Carlo simulations. [Work supported by ONR.]
Exploring the capabilities of an 18-kHz split-beam scientific echosounder for water column mapping and seafloor positioning of methane seeps in the northern Gulf of Mexico
Authors: Jerram Kevin , Weber Thomas C. , Beaudoin Jonathan
Published: September 2012

Underwater methane seeps support diverse biological communities on the seafloor and, in cases of bubble survival to the surface, contribute to the quantity of atmospheric methane. The National Oceanic and Atmospheric Administration (NOAA) ship Okeanos Explorer completed two research cruises for seep mapping and characterization in the northern Gulf of Mexico during August and September of 2011 and April of 2012. A 30-kHz Kongsberg EM 302 multibeam echosounder (MBES) and an 18-kHz Simrad EK60 split-beam scientific echosounder were employed to detect and observe seeps during multiple transects over areas of known seep activity at depths of approximately 1500 m. This presentation includes analyses of EK60 data from both research cruises with emphasis on seep mapping in the water column and seep source positioning on the seafloor using EM 302 MBES observations of seeps as benchmarks. Uncertainty associated with interferometric principles employed by the EK60 and limits to midwater positioning capability imposed by its beam pattern are discussed. The importance of sound speed measurement at the transducer face and the effects of refraction correction are estimated by comparison of isovelocity and constant-velocity layer models using sound speed profiles collected during the research cruises.
An introduction to the Biomedical Acoustics Technical Committee
Authors: McGough Robert
Published: September 2012

An overview of the activities of the Biomedical Acoustics Technical Committee will be presented, along with a brief survey of some of the ongoing research projects in Biomedical Acoustics. For example, the Biomedical Acoustics Technical Committee organizes a student poster competition every year, and special sessions are arranged at each meeting to highlight some of the latest research in the diagnostic and therapeutic applications of acoustics. Some of the topics include ultrasound imaging, high intensity focused ultrasound, ultrasound mediated drug delivery, ultrasound contrast agents, ultrasound-induced cavitation, and ultrasound elastography, among several others. In this presentation, selected examples of active research topics in Biomedical Acoustics will also be described in greater detail.
An introduction to current research in Speech Communication
Authors: Bent Tessa
Published: September 2012

Speech is a highly complex acoustic signal yet most people can produce and understand speech rapidly and without error. Researchers in Speech Communication—including speech and hearing scientists, linguists, psychologists, and engineers—are deepening our understanding of this amazing process. Topics covered by the Speech Communication Technical Committee include speech production, perception, and acquisition; acoustic phonetics; speech and hearing disorders; neuroscience of speech production and perception; speech intelligibility; communicative aspects of singing; speaker classification and identity; audiovisual speech perception; and speech processing and technology. This presentation will provide a brief overview of some current research areas within Speech Communication including speech acquisition in first language, second language, and bilingual contexts; the impact of speech and hearing disorders on communication; imaging and modeling of speech production using new technologies; and adaptation to novel speech stimuli throughout the lifespan.
Introduction to the Structural Acoustics and Vibration Technical Committee
Authors: Phillips James E.
Published: September 2012

The Structural Acoustics & Vibration Technical Committee (SAVTC) includes the study of motions and interactions of mechanical systems with their environments and the methods of their measurement, analysis, and control. This talk will provide a broad overview of the many research areas of interest to SAVTC. A few topics will be explored in more depth to provide background on some of the more common analysis methods used by members of the technical committee.
Noise and its impact on our world
Authors: Ryherd Erica
Published: September 2012

Noise invades all aspects of our lives. The word noise is actually derived from the Latin word “nausea”, with one possible connection being that unpleasant sounds were made by seasick passengers or sailors in ancient times. In modern times, the demand for noise research and consulting has intensified in concert with rising population densities, growing industrialized societies, escalating demands from consumers, and increasingly common standards and legislation related to noise. The Acoustical Society of America Technical Committee on Noise (TC Noise) is concerned with all aspects of noise, ranging from noise generation and propagation, to active and passive methods of controlling noise, to the effects of noise on humans and animals. This talk will explore the broad topic of noise and its impact on our world.
An introduction to the Underwater Acoustics Technical Committee
Authors: Isakson Marcia J.
Published: September 2012

Acoustics is considered the best means of remote sensing in oceans, lakes, and estuaries due to the high attenuation of electromagnetic radiation in water. The members of the underwater acoustics technical committee are concerned with the generation and propagation of sound in an underwater environment as well as acoustic reflection and scattering from the seabed, sea surface and objects in the water column and on or beneath the seabed. In this talk, a short history of underwater acoustics will be followed by an overview of the current state of research in the field.
Estimation of blast noise sound fields over large regions using noise monitors and geostatistical models
Authors: Nykaza Edward T. , White Michael J. , Wilson D. Keith , Atchley Anthony A.
Published: September 2012

This study explores the feasibility of accurately estimating blast noise levels over a large region between and beyond noise monitoring stations using geostatistical models. The potential improvements over propagation modeling include faster computations, fewer assumptions, and improved accuracy. The estimation models explored include kriging, simple interpolation, and models that include meteorological and terrain parameters commonly incorporated into outdoor sound propagation models. The estimation models are evaluated using both experimentally measured and simulated noise monitor data gathered under various atmospheric conditions in several large regions (e.g., greater than 16 km2). The performance of using geostatistical-based estimation models is discussed in terms of the uncertainty of sound pressure field estimates, sensitivity to atmospheric variability, sensor density and geometry configuration, and model validation.
A single-bounce method for estimating impulse propagation and attenuation in a forest
Authors: Swearingen Michelle E. , Albert Donald G.
Published: September 2012

There are numerous methods for determining the impact of interactions with multiple scattering objects on a propagating signal. Many of these methods assume that the signal is continuous in time, allowing one to neglect time dependence. Additionally, these methods make assumptions about the spatial distribution of scattering objects, such as lattice or random, and many assume that the scattering objects are all identical. Real forests often have trees of varying trunk diameters and may be arranged in a grid, in clusters, or random, and the assumptions of uniform size and particular spatial distributions introduce error into the assessments. A simple model, based on single bounces from trunks, is developed to begin estimating the propagation of an impulsive signal through this complicated multiple scattering environment. The scattering algorithm takes the frequency-dependent radial scattering pattern of a cylinder into account. Results are compared to data collected in a forest stand where the locations and diameters of trunks were carefully recorded. These comparisons provide insight into whether a single, discrete bounce method is sufficient for modeling impulse propagation in this complex environment, or whether multiple discrete bounces or some other method should be explored.
Acoustic and optical characterization of ultrasound contrast agents via flow cytometry
Authors: Perez Camilo , Brayman Andrew , Tu Juan , Swalwell Jarred , Chen Hong , Matula Tom
Published: September 2012

Characterizing ultrasound contrast agents (UCAs) involve measuring the size and population distribution. However, these instruments do not allow for characterization of shell properties, which are important for (1) stability to administration and circulation throughout the vasculature; (2) UCA response to ultrasound; and (3) conjugating ligands for molecular imaging. Thus it is critical to understand the physical and rheological properties of shells. We previously developed a light scattering technique to characterize the shell properties of UCAs [Guan and Matula, JASA, Vol 116(5), 2004; Tu, et al., IEEE Trans. Ultrason., Ferroelec., and Freq. Control, vol. 58(5), 2011]. The most recent manifestation involves a flow cytometer modified with a custom square quartz flow cell in place of the standard nozzle and fluid jet. Acoustic coupling to the carrier sheath fluid and UCA samples occurred through a PZT bonded to one side of the flow cell. The PZT-driven UCA oscillations were processed and fitted to the Marmottant UCA model. Shell properties for UCAs (including Definity, Optison, SonoVue, and even homemade bubbles) were determined. The focus of this talk will be on pressure calibration and additional measurements of unpublished data from Optison and homemade bubbles. (Funded in part by the Life Sciences Discovery Fund #3292512)
Engineering tissues with ultrasound heating, radiation force, and cavitation
Authors: Dalecki Diane , Hocking Denise C.
Published: September 2012

Wesley Nyborg was a pioneer in the field of biomedical ultrasound. His theoretical and experimental work forms the foundation for our understanding of the biological effects of ultrasound. He developed fundamental theories of the physical mechanisms of interaction of ultrasound with tissues, including heating, radiation force, and cavitation. In this presentation, we discuss our development of three ultrasound technologies that employ heating, radiation force, or cavitation to address important challenges in tissue engineering. One technology uses radiation forces developed in an ultrasound standing wave field to spatially pattern cells within engineered tissues. The resultant ultrasound-induced patterning can lead to extracellular matrix remodeling, collagen reorganization, and the rapid formation of a vascular network. A second technology uses ultrasound to control the microstructure of collagen within engineered tissues via a thermal mechanism. Through control of ultrasound heating, engineered tissues can be fabricated with spatial variations in collagen microstructures. The structure of extracellular matrix proteins directs cell behaviors important for tissue formation. In the third technology, ultrasound is used to alter the conformation of another extracellular matrix protein, fibronectin, likely through a cavitation mechanism. These studies highlight how fundamental principles of ultrasound-tissue interactions can be used to develop novel tools for tissue engineering.
Nucleating and sustaining acoustic cavitation for biomedical applications
Authors: Porter Tyrone M.
Published: September 2012

Wes Nyborg was a pioneer in the field of biomedical ultrasound. In particular, Nyborg conducted extensive studies that provided insight into how bubbles oscillating in liquids generated forces that could alter the anatomy and/or physiology of cells. While these studies demonstrated that acoustic cavitation is instrumental in a variety of bioeffects, nucleating and sustaining acoustic cavitation in a controlled manner has proven to be a challenge, particularly in vivo. Studies have shown that these challenges can be addressed with the use of novel materials, particles, and/or acoustic pulsing schemes. In particular, pH-sensitive polymers with varying hydrophobicity have been used to sustain cavitation/cell interactions and vaporizable perfluorocarbon nanoemulsions have been used to reduce the pressure threshold for cavitation nucleation. The impact of these materials and particles on cavitation-mediated bioeffects will be discussed.
Tracking the motion of cavitation bubbles using pulsed Doppler
Authors: Everbach E. C.
Published: September 2012

Echo-contrast agent microbubbles in blood can sometimes penetrate a clot that is blocking bulk flow in the vessel. When ultrasound is applied for the purpose of sonothrombolysis, microbubbles can be forced by acoustic radiation force into the clot matrix. To monitor the extent of this penetration, a 20 MHz pulsed Doppler method was employed to measure both the position of the bubble front in the clot and its velocity. Correlations between clot dissolution and the location of the advancing microbubble front may be used to optimize cavitational activity and improve sonothrombolysis.
Computation of backscattering enhancements by a half-exposed rigid cylinder at a free surface caused by Franz waves
Authors: Smith Anthony R. , Plotnick Daniel S. , Eastland Grant C. , Marston Philip L.
Published: September 2012

Recent observations of the backscattering by partially-exposed solid aluminum cylinders in water viewed at grazing incidence at a free surface [G. C. Eastland, Ph.D. thesis, Wash. State Univ., 2012] indicate that the generation, propagation, and reflection of Franz-type creeping waves can be important. The present investigation gives additional support for this hypothesis by calculating the exact backscattering by a half-exposed infinitely long rigid cylinder viewed over a range of grazing angles. The calculation begins with the known frequency domain expression for the complex amplitude given in an Appendix of [K. Baik and P. L. Marston, IEEE J. Ocean. Eng. 33, 386 (2008)]. Numerical Fourier transforms were used to construct the time-domain response for various excitations and the evolution of that response was investigated as a function of the grazing angle. This procedure reveals from the timing of the computed features there is a significant delayed echo having the expected timing of a Franz wave partially reflected from the free surface. The timing of the Franz wave depends on grazing angle in agreement with a geometric model in Eastland’s thesis. [Supported by ONR.]
Scattering of low-frequency spherical waves by fluid and solid spheres
Authors: Godin Oleg A.
Published: September 2012

Acoustic Green’s functions for a homogeneous fluid with an embedded spherical obstacle arise in analyses of sound scattering by air bubbles, scattering by objects on or near the seafloor, radiation by finite sources, sound attenuation in and scattering from clouds of suspended particles, etc. Here, radius of the obstacle is assumed to be small compared to the wavelength of sound. This regime is usually referred to as Rayleigh scattering. A new, elementary solution of the problem of diffraction of a spherical wave was recently obtained for small, soft obstacles [O. A. Godin, J. Acoust. Soc. Am. 37, L13605 (2010)]. The solution is valid for arbitrary positions of the source and receiver relative to the obstacle. In this paper, the solution is extended to homogeneous and inhomogeneous fluid and solid spheres. Low-frequency scattering is found to be rather sensitive to boundary conditions on the surface of the obstacle. Resonance scattering of spherical waves by small spheres is investigated. [Work supported, in part, by ONR.]
Fast model for target scattering in a homogeneous waveguide
Authors: Kargl Steven G. , Williams Kevin L. , Espana Aubrey L.
Published: September 2012

A fast ray model for propagation in a homogenous water column tracks time-of-flight wavepackets from sources to targets and then to receivers. The model uses image sources and receivers to account for interactions with the water column boundaries, where the layer of water lies between an upper semi-infinite halfspace of air and a lower semi-infinite halfspace of a homogenous sediment. The sediment can be either an attenuating fluid with a frequency-independent loss parameter or a fluid consistent with an effective density fluid model (i.e., a fluid limit to Biot's model for a fluid-saturated poroelastic medium). The target scattering process is computed via convolution of a free-field scattering form function with the spectrum of an incident acoustic field at the target location. A simulated or measured scattered free-field pressure from a complicate target can be reduced to a scattering form function, and this form function then can be used within model via interpolation. The fast ray-based model permits the generation of sets of realistic pings suitable for synthetic aperture sonar processing for proud and partially buried target. Results from simulations are compared to measurements where the targets are an inert unexploded ordnance and aluminum cylinder. [Research supported by SERDP and ONR.]
Supervised machine learning for classification of underwater target geometry from sampled scattered acoustic fields in the presence of rough bottom interference
Authors: Fischell Erin M. , Schmidt Henrik
Published: September 2012

An increasingly important mission for Autonomous Underwater Vehicles (AUVs) is the identification and classification of potentially hazardous targets in harbors. A process is demonstrated in simulation that would allow AUV in-flight classification of spherical and cylindrical targets using only scattered acoustic amplitudes collected at waypoints. Target and bottom roughness scattered fields are simulated using OASES and SCATT, then combined and sampled into independent training and testing examples for a Support Vector Machine (SVM). The feature space and parameters for the SVM are selected using a design of experiments grid search. By processing the model using a feature reduction algorithm, it is possible to identify the regions in the scattered field that are the most critical for classification. To make use of the resulting models and critical features, a vehicle in the field would be loaded with pre-generated models for bottom and target classification. Upon target localization, the vehicle would begin visiting the critical waypoints until a confident classification is achieved using the SVM models. The resulting in-flight classification, based only on amplitude data collected by a hydrophone along the vehicle's path, could be used as the basis for further action on the target. [Work supported by ONR and NSF GRFP.]
Simulating coherent backscatter enhancement from aggregations of underwater scatterers
Authors: Mookerjee Adaleena , Dowling David R.
Published: September 2012

Remote classification of scatterers is an enduring priority in active sonar applications. For aggregations of marine life, typically schools or shoals of fish, remote classification may be possible when there is coherent backscattering enhancement (CBE) from the aggregation. CBE is a multiple scattering phenomenon that occurs in optics and acoustics when wave propagation paths within the aggregation are likely to be traversed in both directions. For a plane wave illuminating a half-space of randomly-placed, omnidirectional scatterers, CBE may lead to a doubling of the scattered field intensity in the direction opposite that of the incident wave (Akkermans et al. 1986). This presentation describes acoustic CBE simulations for finite-size spherical aggregations of point scatterers. The results are developed from the classical multiple-scattering equations of Foldy (1945), and are checked to ensure appropriate rotational symmetries and acoustic energy conservation when scatterer locations are random and when they are structured. Variations in the magnitude of the CBE peak and its angular width are presented for different frequencies, aggregation sizes, scatterer densities, and scatterer properties. Extension of these results to sonar-pulse scattering from schools of fish will be discussed. [Supported by the Office of Naval Research.]
Frequency response of ordnance replicas across multiple scales
Authors: Dudley Christopher , Kennedy Jermaine , Lee Kwang , Malphurs David
Published: September 2012

Broad-band, multi-aspect backscatter data obtained using small-scaled and full-scaled replicas of Unexploded Ordnance (UXO) are reported. Data were collected using either linear or circular rail systems. The experiments were performed in: (1) NSWC PCD's small scale test bed (less than 1/16 scaled) which has a simulated bottom, (2) NSWC PCD's Facility 383 9-million gallon fresh water test pool which has a 5-ft sand bottom, and (3) the Gulf of Mexico during GULFEX12 off Panama City, Florida. Data were processed using linear and circular synthetic aperture sonar techniques to generate both images and plots of target strength as functions of frequency and aspect angle. The results from all three experiments are compared to each other and with predictions from Finite-element (FE) analysis. These comparisons are used to assess the utility of alternative methods for generating sonar data from bottom targets of sufficient fidelity to study scattering phenomena and support development of automated target recognition. [Work supported by ONR Code 32 and SERDP.]
Modeling binaural processing: What next?
Authors: Blauert Jens
Published: September 2012

Models of binaural processing are traditionally based on signal-processing in a bottom-up (signal-driven) architecture. Such models are sufficient for a number of technologically important applications, such as perceptual coding, sound-source identification and localization, dereverberation and decoloration, but fail when applications require cognition. Future models will thus include symbol processing in addition to signals processing, will have inherent knowledge bases and employ top-down (hypothesis-driven) strategies in addition to bottom-up ones. Some of these features are known from automatic speech recognition and may be generalized for broader application, e.g., blackboard structures. With the new models more sophisticated applications may be approached, for instance, quality evaluation and assessment on the basis of internal references, such as needed to determine estimates of the quality of performance spaces and/or audio systems. Further, to enable autonomous learning, future models will employ feed-back loops to realize active exploratory actions. Some of these features can be imported from recent research in robot audition. In our contribution, we shall, among other things, report on ideas and concepts as currently discussed in AABBA, an international grouping of 14 laboratories in Europe and the US that are dealing with auditory assessment by means of binaural algorithms.