bluuebunny/crossref_metadata_2025 huggingface dataset:
Time reversal acoustic focusing with liquid-filled reverberator
Authors: Sinelniov Yegor , Vedernikov Andrey , Sutin Alexander , Sarvazyan Armen
Published: October 2013

The use of solid acoustic reverberators for temporal and spatial focusing of acoustic energy based on time reversal acoustic (TRA) principle was described in the literature. We experimentally and theoretically demonstrated that the liquid-filled TRA reverberators can also efficiently focus acoustic energy and compared the advantages of solid and water-filled reververators. A theoretical model was developed to explore the factors defining the efficiency of TRA focusing, providing the design constraint for the water-filled reververators. The model allows evaluation of the spatial and temporal characteristics of TRA focused acoustic field formed as a result of numerous reflections of ultrasound within the reverberator. The TRA focused field structure, its dependence on the shape and size of the resonator, ultrasound frequency, and attenuation were investigated for the standard and binary modes of TRA focusing. The experiments with custom built liquid-filled acoustic resonators confirmed the predictions of a developed theory, including sharpening of the focal area and increasing of the focal intensity in a binary mode of TRA focusing. The conducted research supports suggestion that such liquid-filled reverberators can be considered as a base for a miniature limited range ablation devices for biomedical applications.
Stress and strain relaxation mechanisms in soft tissue: An inverse problem and solution
Authors: Leiderman Ricardo , Berry Gearoid P. , Bamber Jeffrey C. , Oberai Assad A. , Barbone Paul E.
Published: October 2013

Elastography refers to a collection of ultrasound imaging techniques that allow mechanical strain distributions to be imaged and noninvasively quantified in vivo. The time scales over which the tissue response is typically measured range from about a millisecond (the typical duration of a radiation force ‘‘push pulse’’) to about one second (the typical time scale of freehand quasistatic compression) used in strain imaging. Soft tissue is widely recognized as having both fluid and solid phases which can move independently of each other, giving rise to stress/strain relaxation effects. Furthermore, the fluid exists within several ‘‘compartments’’ of the soft tissue, notably, the vasculature (including both the hemal and lymphatic vessels) and the extravascular space (i.e., the interstitium). Of course, due to permeability of microvessel walls in both vascular networks, fluid is often exchanged between these compartments. Through mathematical models of tissue deformation, we explore the macroscopic effects of different microscopic relaxation mechanisms. We show that different microscopic relaxation mechanisms result in different spatio-temporal patterns of strain relaxation. We then focus on one such mechanism, and we formulate and solve an inverse problem that measures the microvessel density and permeability from the time-history of a measured strain distribution.
Is the Kramers-Kronig causal relationship between ultrasonic attenuation and dispersion maintained when phase aberrations distort the field incident on a phase sensitive aperture?
Authors: Bauer Adam Q. , Marutyan Karen R. , Holland Mark R. , Miller James G.
Published: October 2013

The objective of this investigation was to determine whether the causality-induced link between ultrasonic attenuation and dispersion remains valid when the measured signal loss arises as a consequence of phase cancellation at the face of a phase-sensitive receiver rather than from intrinsic losses within the medium under study. The frequency-dependent apparent attenuation and phase velocity were obtained from through-transmission measurements of two flat and parallel plastic polymer plates, PlexiglasTM and LexanTM, exhibiting an approximately linear with frequency attenuation coefficient and logarithmic with frequency phase velocity. Phase distortion was achieved by machining a step into one side of each plastic plate. Through-transmission measurements were performed in a water tank using 5 MHz center frequency single element planar transmitting and receiving transducers. The causal (Kramers-Kronig) link between apparent phase velocity and the apparent attenuation coefficient in the presence of phase distortion was examined for both plastics over a bandwidth ranging from 3 to 7 MHz. Results demonstrate that the Kramers-Kronig link between the apparent attenuation coefficient and apparent phase velocity dispersion remains causally consistent even in the presence of aberrating media.
Three dimensional ultrasound elasticity imaging
Authors: Richards Michael S. , Rubin Jonathan M. , Oberai Assad A. , Barbone Paul E.
Published: October 2013

The aim of our work is to develop and evaluate an ultrasound (US) technique to quantitatively measure and image the shear modulus of soft tissues in three dimensions (3D). It is widely recognized that breast tissue pathologies, such as neoplasia, often alter biomechanical properties. Thus, the intended application of our work is the detection and characterization of breast tissue lesions, via elastic modulus imaging, to improve the specificity of breast cancer screening. To that end, we have designed and characterized algorithms which 1) provide 3-D motion estimates from 3-D US images and 2) solve the 3-D inverse problem to recover shear elastic modulus. The size and contrast accuracy of the reconstructed modulus distributions in tissue mimicking phantoms are presented. Inclusions as small as 5mm, some with contrasts marginally above unity, were successfully and clearly reconstructed. The effect of the boundary conditions and regularization methods on the reconstructed modulus images and the uniqueness of the solution are also discussed. In addition, preliminary modulus reconstructions created from clinical 3-D US breast images acquired in a mammography mimicking system are presented.
Swimmer detection sonar network
Authors: Stein Peter J. , Vandiver Amy , Edelson Geoffrey S.
Published: October 2013

The Swimmer Detection Sonar Network (SDSN) was designed to be a cost effective method to protect a large area from terrorist swimmers. The in-water system consists of a number of sonar nodes, each consisting of a set of air-backed parabolic dish transducers that are used to both transmit and receive in sets of independent narrow beams. Each dish/channel can transmit and process its own unique signal. The Sonar Network is therefore composed of a distributed group of nodes each providing a set of independent narrow-beam sonars. This allows for strong rejection of interfering clutter, resulting in excellent performance. The nodes/channels are also synchronized, allowing for multi-static signal processing. A suite of signal processing algorithms has been developed for automated detection, tracking, and classification, including a fine-bearing estimation that achieves approximately 1 deg accuracy. These algorithms will be discussed. Data will be shown that shows the performance against swimmers and the possibilities for bi-static detection and classification. The SDSN has been productized and is now available for wide-scale deployment. It is a cost effective means for large harbor facilities to reliably detect underwater threats at long ranges.
Detection and target echo enhancement in shallow water using the Decomposition of the Time Reversal Operator
Authors: Prada Claire , de Rosny Julien , Clorennec Dominique , Minonzio Jean-Gabriel , Aubry Alexandre , Fink Mathias , Bernière Lothar , Hibral Sidonie , Billand Philippe , Folégot Thomas
Published: October 2013

A rigid 24-element source-receiver array (SRA) in the 10 to 15 kHz frequency band, connected to a programmable electronic system was deployed in the bay of Brest (France) during spring 2005. In this 10 to 18 m deep environment, backscattered data from submerged targets were recorded. Successful detection and focusing experiments in very shallow water using the Decomposition of the Time Reversal Operator (DORT method) are shown. The ability of the DORT method to separate the echo of a target from reverberation is demonstrated. For a target close to the bottom at 350 m range, active focusing using the first invariant of the time reversal operator was achieved, showing a target echo enhancement. Furthermore, the localization of the target in the water column is obtained using RAM [Collins et al., J. Acoust. Soc. Am. 89 3 (1991)]. [Work supported by the French DGA/SPN under contract number 02 77 154 00 470 75 53.] a)now affiliated to NATO Undersea Research Centre, La Spezia, Italy
Estimation of passive acoustic threat detection distances in estuarine environments
Authors: Borowski Brian , Roh Heui-Seol , Bunin Barry , Sutin Alexander
Published: October 2013

The Maritime Secure Laboratory (MSL) at Stevens Institute of Technology supports research in a range of areas relevant to harbor security, including passive acoustic detection of underwater threats. The difficulties in using passive detection in an urban estuarine environment include intensive and highly irregular ambient noise and the complexity of sound propagation in shallow water. MSL measured the main parameters defining the detection distance of a threat: source level of a scuba diver, transmission loss of acoustic signals, and ambient noise. The source level of the diver was measured by comparing the divers sound with a reference signal from a calibrated emitter placed on his path. Transmission loss was measured using the transmission of a sweep signal (1–100 kHz) from the calibrated emitter. The passive sonar equation was then applied to estimate the range of detection. Estimations were done for various recorded noise levels, demonstrating how fluctuations in noise level and the mobility of the diver influence the effective range of detection. Finally, analytic estimates of how a hydrophone array improves upon the detection distance calculated by a single hydrophone are shown. [This work was supported by ONR project No. N00014-05-1-0632: Navy Force Protection Technology Assessment Project.]
Improved range and characterization of harbor security systems through bistatic detection
Authors: Isakson Marcia , Bown Colin , Rehn Karl , Crowe Nathan
Published: October 2013

There are three critical design drivers for harbor security systems: cost per unit area of coverage, coverage of geometrically denied areas such as very shallow waters and under and around piers, and probability of false alarm. Bistatic detection can address all three of these issues. First, many harbor security systems operate with overlapping coverage. These adjacent systems offer an existing source of bistatic signals. By analyzing the signal from these adjacent sources, the coverage for each sound head is increased with no increase in system cost. Second, the strategic placement of additional sources will allow coverage in denied areas for little additional cost. Lastly, additional detection will lower false alarm rates. In this study, measurements from an overlapping harbor security system will be analyzed to determine the effect of additional bistatic analysis on detection thresholds and coverage range.
Singers’ self-perception of harmonics
Authors: Popeil Lisa
Published: October 2013

Historically, singers have relied on the sensation of resonance as a guide in vocal production. The use of terms such as focus and placement have been primary tools in traditional vocal pedagogy. In a newer method of acoustic training, singers can be taught to discern three bands of harmonics which are key elements of vocal timbre: ring, brightness, and nasality. Each of these harmonic bands has particular sonic and expressive characteristics and are easily amplified or attenuated. Ring, at 2500–3500 Hz, is the most penetrating of the three and is acutely heard by the human ear. Ring aids singers in being heard without electronic amplication. Brightness, comprised of harmonics in the approximate range of 5–15 kHz, lacks the penetrating quality of ring but is an important conveyor of the emotion of happiness and expressive traits such as sincerity and innocence. Nasality, broadly occuring in the 200–2000 Hz range, has a characteristic buzziness and is used in commercial singing styles for amplitude and expressive enhancement. Live vocal demonstrations will show how a singer can create, isolate, and combine ring, brightness, and nasality.
The 1:6 ratio in vocal pedagogy
Authors: Monson Brian B.
Published: October 2013

The so-called singer’s formant or singer’s formant cluster is created in the vocal tract by a narrow epilaryngeal tube opening, such that the ratio of the cross-sectional area of the pharynx is approximately six times greater than that of the epilarynx outlet. This appears to be accomplished by maintaining a comfortably low laryngeal position while manipulating other structures of the vocal tract. Experimental research was conducted to examine the potential of pedagogical implementation of this principle. Experimentation consisted of training graduate voice student subjects at Brigham Young University to use the one-to-six ratio to achieve the singer’s formant. Using the acoustical output from the singers for analysis, predictions of actual vocal tract shapes before and after vocal tract manipulation will be shown. The results of this study may offer valuable information regarding the training of voice students to access the singer’s formant.
Source-vocal tract interaction in singing
Authors: Titze Ingo R.
Published: October 2013

It has been known for centuries that certain vowels are easier to sing on certain pitches. Much of traditional and modern singing pedagogy is focused on this vowel F0 interaction. Unlike most musical instruments, where the resonator is specifically designed to resonate many of the source frequencies at every note played, the vocal instrument relies on the use of inertive reactance (away from resonance) to boost various clusters of harmonics. Acoustic reactance is positive (inertive) below a vocal tract resonance (a formant), zero at resonance, and negative (compliant) above resonance. The skill in selecting a vowel for a given F0 is to place as many of the key harmonics (2F0, 3F0, and 4F0) on the inertive portions of the reactance curves. The process is aided by shrinking the epilarynx tube, which biases the reactance curves toward positive values over the entire F0 range. [Work supported by NIDCD.]
Bulk versus nanoscale WS2: Finite size effects and solid state lubrication
Authors: Musfeldt J. L. , Brown S. , Mihut I. , Betts J. B. , Migliori A. , Zak A. , Tenne R.
Published: October 2013

Metal dichalcogenide nanostructures have recently attracted attention due to their unique closed-cage structures, hierarchy of length scales, and outstanding solid state lubrication behavior. To understand the finite size effects and tribological properties in these nanoscale materials, we measured the low temperature specific heat of layered and nanoparticle WS2. Below 9 K, the specific heat of the nanoparticles deviates from that of the bulk. Further, the thermal response of the nested nanoparticles deviates from the usual T3 dependence below 4 K because of both finite size effects and inter-particle-motion entropy. This separation of nanoscale effects from T3 dependence can be modeled by assuming that the phonon density of states is flexible, changing with size and shape of the nanoparticle. We also invoke relationships between the low temperature T3 phonon term, Young’s modulus, and friction coefficient to assess the difference in the tribological properties. Based on this analysis, we conclude that the improved lubrication properties of the nanoparticles are extrinsic in origin.
Magnetoacoustic studies as a probe of electron systems
Authors: Suslov Alexey
Published: October 2013

The pulse-echo technique was used to probe the electron systems in solids. The measurements were performed in the frequency range 10–500 MHz, at temperatures down to 0.3 K and in the magnetic fields up to 18 T. (a) Acoustic quantum oscillations were investigated in URu2Si2, AuZn, and Sr2RuO4. Extracted parameters of the electron systems are in good agreement with data known from other experiments and theoretical calculations. Hydrostatic pressure effect on superconductive transition in Sr2RuO4 was studied. It is found that the sound speed increases, critical temperature and critical fields decreases, and transition becomes broader under the pressure. Magnetic field dependencies of ultrasound attenuation are compared with theoretical predictions. (b) Surface acoustic waves were used for contactless measurements of conductivity in low dimensional structures. The value of complex ac conductivity was extracted from simultaneous measurements of the sound attenuation and velocity. Such measurements allowed to study, for example, mechanisms of conductivity in a dense array of SiGe quantum dots and localization of the 2D carries in GaAs/AlGaAs and Si/SiGe heterostructures in the extreme quantum limit. NHMFL is supported by the NSF Cooperative Agreement No. DMR-0084173 and the State of Florida. The ultrasonic research at the NHMFL is supported by the In-House Research Program.
Scattering methods applied to lattice dynamics in thermoelectric materials
Authors: Hermann Raphaël P.
Published: October 2013

Inelastic neutron scattering and x-ray scattering or nuclear resonance scattering are powerful techniques that yield insight into the microscopic origin of macroscopic material behavior. Progress in nuclear resonance scattering that allows element specific studies of lattice dynamics and, in particular, element specific measurements of the phonon density of states, atomic displacement parameters, and force constants, will be discussed. Recent results from lattice dynamics studies of thermoelectric materials, such as filled skutterudites, clathrates, and Zn4Sb3, will be presented in conjunction with results from macroscopic determinations of the thermodynamical properties of these materials, such as heat capacity or elastic constants obtained by ultrasound spectroscopy. [The European Synchrotron Radiation Facility is acknowledged for provision of the synchrotron radiation facility at beamlines ID18 and ID22N. Part of this research was carried out at the FRJ-II research reactor in Jülich, Germany.]
Elasticity in metallic glasses
Authors: Egami Takeshi , Levashov Valentin , Aga Rachel , Morris Jamie J.
Published: October 2013

The unique nature of elasticity in metallic glasses will be discussed with particular focus on the intrinsic anelasticity. Although the bulk modulus of a metallic glass is comparable in magnitude to that of the corresponding crystalline solid, the shear modulus is always lower by 20% to 30%. This is because shear deformation of a metallic glass produces not only the geometrical deformation but also local topological changes of atomic bonding. Even in the glassy state there is some local residue of liquidity due to local structural frustrations, and this makes the shear deformation in metallic glasses intrinsically anelastic. On this point glasses are fundamentally different from crystals. This intrinsic anelasticity results in anomalous dependence of shear modulus and anelastic loss on frequency and temperature, including the low-temperature two-level state behavior. Based upon computer simulation, neutron scattering experiment, and theory, the intrinsic nature of anelasticity will be shown to be a part of the big picture of the structure and dynamics of metallic glasses.
Determination of third-order elastic constants of langasite single crystals through force-frequency effect
Authors: Zhang Haifeng , Turner Joseph A. , Yang Jiashi , Kosinski John A.
Published: October 2013

Langasite resonators are of recent interest for a variety of applications because of their good temperature behavior, good piezoelectric coupling, low acoustic loss, and high Q factor. Third-order elastic constants are responsible for many nonlinear effects associated with langasite resonators including the force-frequency effect. This effect describes the shift in resonant frequency a resonator experiences due to the application of a mechanical load. The determination of the third-order elastic constants through the force-frequency effect relies on an accurate theoretical understanding of this effect. In this article, expressions for the frequency shift of langasite resonators subjected to a pair of diametric forces are obtained using the perturbation integral in conjunction with the finite element method. Experimental measurements of the force-frequency effect for various langasite resonator samples with plano-plano configuration are also discussed. The third-order elastic constants of langasite single crystals are extracted based on the measured data in conjunction with the derived expressions. The results are compared with previous measurements of third-order elastic constants for langasite obtained using transit-time methods. [Work supported by ARO.]
Why pitch strength decreases with increasing harmonic number in complex tones
Authors: Ives D. Timothy , Patterson Roy D.
Published: October 2013

A melodic pitch experiment was performed to demonstrate the importance of temporal resolution for pitch salience. The experiments show that notes with a low fundamental (75 Hz) and relatively few resolved harmonics support better performance than comparable notes with a higher fundamental (300 Hz) and more resolved harmonics. Two four-note melodies were presented to listeners and one note in the second melody was changed by one or two semitones. Listeners were required to identify the note that changed. There were four orthogonal stimulus dimensions: F0 (75 and 300 Hz), lowest frequency component (3, 7, 11, or 15), number of harmonics (2, 4, or 8), and degree of component rove (1 or 3). Performance decreased as the frequency of the lowest component increased for both F0s, but performance was better for the lower F0. The spectral and temporal information in the stimuli were compared using the Auditory-Image Model [Bleeck et al., Acta Acust. 90, 781–788 (2004)]. Peaks in the time-interval profile of the auditory image can explain the decrease in performance as F0, and spectral resolution increase. Spectral profiles of the same auditory images do not contain sufficient resolution to explain the performance. [Work supported by U.K. MRC (G0500221, G9900369).]
The effect of phase, fundamental, and lowest component on the perception of octave height
Authors: van Dinther Ralph , Patterson Roy D.
Published: October 2013

Attenuation of the odd harmonics of a complex harmonic tone increases the perceived octave height and eventually leads to a shift of one complete octave in the perception. In a 2AFC experiment, we assessed how much the odd harmonics had to be attenuated to make a sound indistinguishable from its octave, first when the components were in cosine phase and then when the phase of the odd harmonics was shifted by 1/3π or 1/2π. Thresholds were measured for four fundamental frequencies (31, 63, 125, 250 Hz) and four lowest harmonic numbers (2, 4, 8, 16). The results show that when the odd harmonics are phase shifted, the attenuation required to make the test sound indistinguishable from its octave decreases dramatically, from between 20 and 30 dB to less than 5 dB. A model based on the time-interval profile of the auditory image [Patterson, J. Acoust. Soc. Am. 98, 1890–1894 (1995)] was used to explain the data; 95% of the predicted thresholds fall within one standard deviation of the empirical data. The spectral profile did not have sufficient resolution to predict the data and it could not explain the effect of the phase manipulation. [Work supported by the U.K. Medical Research Council (G0500221, G9900369).]
The effect of interaural differences of time on speech intelligibility in simulated electric-acoustic hearing
Authors: Brown Christopher A. , Bacon Sid P.
Published: October 2013

Individuals with residual hearing restricted to frequencies below about 500–750 Hz have recently been implanted with a relatively short electrode array designed to preserve as much of the residual hearing as possible. Those who also have some low-frequency hearing in the non-implanted ear have the potential to benefit from interaural time differences (ITD). The goal of the current experiments was to determine whether such benefit exists in simulations of implant listening and how it is influenced by sensation level (SL) in the low frequencies. Presentation was via headphones. Target and distractor speech were low-pass filtered at 500 Hz. The target was presented diotically and the distractor was presented with a 0-s (spatially centered image) or 600-s (image to the right) ITD. The target and distractor were also processed by a four-channel vocoder and presented to the left ear only. The SL of the low-frequency speech was varied both symmetrically and asymmetrically. In the symmetric conditions (15–60 dB SL), intelligibility improved by as much as 40% when the target and distractor were spatially separated. In the asymmetric conditions (60 dB in one ear, 20–50 dB in the other), approximately 15%–20% improvement was observed in all conditions. [Work supported by NIH and NOHR.]
Effects of ear coverage and reflected sound on the localization of sound
Authors: Scharine Angelique , Mermagen Tim , MacDonald Justin , Binseel Mary
Published: October 2013

Previous research has shown that listeners wearing helmets with greater ear coverage perform worse on localization tasks. However, the helmets studied were selected from those commonly in use and differed in suspension systems and profiles. Three versions of the same helmet design, differing only in the ear coverage (0%, 50%, 100%), were compared in this study. Sounds were presented from 12 azimuthal locations spaced 30 deg apart in the presence of a white noise masker. Twelve listeners completed a localization task while wearing each of the helmets as well as with no helmet in two different acoustic environments. As ear coverage increased, localization performance decreased. The effects of early reflections, though small, were consistent across the different coverage conditions. The effect of ear coverage and its interaction with the acoustic environment will be discussed in terms of its significance for real-world environments. In addition, head-related transfer-functions (HRTFs) were measured for each listener in each of the head conditions. A model of localization performance based on changes to the HRTF will be described and applied to the collected data.
Derivation of aeroacoustic environments for the crew exploration vehicle
Authors: Yang Michael
Published: October 2013

The Crew Exploration Vehicle (CEV) is designed to provide safer, more reliable space transportation capability in the quest for human space exploration. This article covers the development of an external aeronoise model which was fit to generic and Saturn/Apollo configuration wind tunnel data, and anchored to Atlas and Titan flight data. The predictions for a combined aerodynamic/propulsion system load case while firing the Launch Abort System (LAS) engines during flight is also presented, along with SEA methods for predicting internal responses.
Prediction of liftoff acoustic environments for launch pads with covered ducts
Authors: Yang Michael
Published: October 2013

The acoustic environment experienced by a launch vehicle is typically most severe during the liftoff phase. The launch pad can be designed with a deflector to redirect the exhaust plume into a covered duct. This is done to reduce the fluctuating pressure field experienced by the vehicle. The Eldred method is frequently used to predict liftoff environments, but does not specify how to model the effects of the covered duct. Techniques used to model the covered duct are reviewed and compared in this paper.
Control of aircraft interior noise using heterogeneous (HG) blankets
Authors: Idrisi Kamal , Johnson Marty , Carneal James
Published: October 2013

This study is concerned with the passive control of vibration and sound radiation of interior cabin noise in aircraft at low frequencies (<500 Hz) using heterogeneous (HG) blankets. HG blankets consist of poroelastic media with small embedded masses, which act similar to a distributed mass-spring-damper system. HG blankets have shown significant potential to reduce low-frequency radiated sound from structures, where traditional poroelastic materials have little effect. A mathematical model of a double panel system with an acoustic cavity and HG blanket was developed using mobility and impedance matrix methods. Theoretical predictions are validated with experimental measurements. Results indicate that proper tuning of the HG blankets can achieve in broadband reductions in sound transmission through the double panel system with less than 10% added mass. Future work includes expanding the model and experiment to multiple panel systems.
Rayleigh waves guided by topography
Authors: Adams Samuel D. M. , Craster Richard V. , Williams Duncan P.
Published: October 2013

It would not be far-fetched to say that the work of Lord Rayleigh on surface guided waves has had fundamental and far-reaching effects upon modern life and many things we take for granted today, stretching from mobile phones through to the study of earthquakes. Many of these things take advantage of surface waves that are topographically guided thereby allowing energy to be carried in specific directions along some topography of the surface. Much of the emphasis has so far been placed on devices which are essentially thin rectangular ridge-like defects upon the surface. Indeed, experiments with these so-called SAW devices have demonstrated the presence of trapped waves. It remains to provide any convincing theory that captures this trapping effect for surface waves—this is our aim. We seek to resolve the issue of whether topography can support a trapped wave, whose energy is localized to within some vicinity of the topography, and to explain physically how trapping occurs. The trapping is first addressed by developing an asymptotic scheme that exploits a small parameter associated with the surface topography. We then provide numerical evidence to support results obtained from the asymptotic scheme; however, no rigorous proof of existence is presented.
Unsteady pressures on a ship hull
Authors: Goody Michael , Farabee Theodore , Lee Yu-Tai
Published: October 2013

Unsteady surface pressure measurements at locations distributed on the surface of a ship model hull and flow visualization of the bow wave and free surface are discussed. The pressure measurement locations are distributed over the hull surface from 15% to 70% of the model length. There are several additional pressure measurement locations on the hull surface adjacent to the bow wave. The measurements were performed in the David Taylor Model Basin using a ship model that is approximately 40 ft long and representative of a naval combatant at Froude numbers from 0.14 to 0.44. The measured surface pressure spectra are compared to predictions done using a RANS-statistical method and predictions done using an empirical formulation that is based on historical, flat-plate, surface pressure spectra. Scaling of the surface pressure spectrum and limited spatial coherence measurements are discussed. [Work sponsored by Office of Naval Research, Code 334.]
Hidden in plain view: Analysis and synthesis of speech features from derivatives of the short-time phase spectrum
Authors: Fitz Kelly
Published: October 2013

The time-frequency reassigned spectrogram has been shown to yield a clean and readable representation of the distribution of energy in speech signals. In this algorithm, precise, signal-dependent loci for time-frequency analysis data are computed from first-order partial derivatives of short-time spectral phase. In this presentation, evidence for the significance of higher-order derivatives of spectral phase will be presented along with algorithms for computing them. It will be shown that harvesting the information in the short-time phase spectrum allows the construction of an enhanced harmonic model of speech signals, having precise instantaneous frequency data for the harmonic components, and greatly reduced temporal smearing relative to traditional additive models. This enhanced model yields high-quality, artifact-free synthesis of sounds from modified and transformed time-frequency data.
Travel time estimation from noisy data in random media
Authors: Papanicolaou George
Published: October 2013

We consider the estimation of Green’s functions, or travel times, from noisy data when the medium is not homogeneous. In the homogeneous case travel times can be estimated from cross correlations of noisy traces at the two points between which the travel time is to be estimated, given information about the nature and extent of the noise sources. In a randomly inhomogeneous medium the noisy traces contain information not only about the homogeneous background but also about the inhomogeneities. It is shown how to assess this effect and the limits it puts on travel time estimation.
Monitoring dynamic matter using the mesoscopic phase statistics of random wave fields
Authors: Page John H. , Cowan Michael L. , Hildebrand W. Kurt , Norisuye Tomohisa , Anache-Menier Domitille , van Tiggelen Bart A.
Published: October 2013

In strongly scattering materials, multiple scattering tends to randomize the phase of transmitted or reflected waves and, as a result, the phase has often been overlooked. In this talk, the use of phase information to monitor the dynamics of multiply scattering media will be described and illustrated through measurements of the temporal fluctuations of ultrasonic waves transmitted through a time-varying mesoscopic sample. The probability distribution of the wrapped phase difference as a function of evolution time, as well as its variance, is measured and compared with theoretical predictions based on circular Gaussian (C1) statistics. Excellent agreement is found. A fundamental relationship between the variance in the phase of the transmitted waves and the fluctuations in the phase of individual scattering paths is predicted theoretically and verified experimentally. This relationship not only gives deeper insight into the physics of the phase of multiply scattered waves, but also provides a new way of probing the motion of the scatterers in the medium. To investigate dynamics on longer time scales, we also investigate the variance and correlations of the cumulative phase. This combination of wrapped and cumulative phase measurements allows both the short and long time dynamics to be probed with excellent sensitivity.
Energy propagation and localization in disordered media
Authors: van Wijk Kasper , Haney Matthew
Published: October 2013

While waves in 3D random media still pose quite the challenge to use in model parameter estimation, the complicated paths of multiply scattered waves can be tracked with greater ease in 1D or quasi-1D media. Applying the model of radiative transfer (RT) to the squared waveforms, I will present results of experimental surface-wave multiple scattering, as well as numerical and theoretical aspects of energy propagation in layered media. In the case of surface-wave scattering, it is possible to estimate the average scattering and intrinsic absorption lengths in a laboratory ultrasonic experiment independently. This may be useful in partial saturated materials such as soils and rock, where intrinsic absorption is often related to the movement of fluids in the pore space. Especially in layered media, multiply scattered waves can interfere with one another. An example of strong wave interference is wave localization. Normally, diffusion and RT do not account for wave interference, but new additional terms in RT for layered media explain wave interference and localization: phenomena. Ultimately, the goal is to extend these results for parameter estimation in random media—once understood fully in lower dimensions—to three-dimensional problems.
Ambient seismic noise and teleseismic tomography in the western USA: High-resolution 3-D model of the crust and upper mantle from Earthscope/USArray
Authors: Yang Yingjie , Ritzwoller Michael , Moschetti Morgan , Forsyth Donald
Published: October 2013

Short-period surface wave dispersion measurements are extremely hard to obtain from teleseismic events due to scattering and attenuation. Ambient seismic noise is rich in short-period surface waves from which the Rayleigh wave Green function between pairs of stations can be extracted by cross-correlating long noise sequences. Tomography based on surface wave dispersion obtained from the estimated Green functions has been shown to produce high-resolution, short-period (6–30 s) surface wave dispersion maps that principally image crustal geological units (e.g., southern California: Shapiro et al., 2006; Europe: Yang et al., 2007). In this study, we measure phase velocity dispersion curves from the ambient noise cross-correlations to obtain phase velocity maps at periods from 6 to 30 using data from the transportable array component of USArray. A two-plane-wave tomography method including finite-frequency effects was employed to obtain phase velocity maps at complementary periods from 25 to 150 using teleseismic events. The combined phase velocity data set from 6 to 150 is used to invert for high-resolution 3-D Vs structure from the surface to ∼ 200 km depth beneath the western USA. The new 3-D Vs model can be used to interpret regional tectonics, model seismic wave propagation, and improve earthquake location.
A qualitative criterion for the reverberant fields for organ music and a means of obtaining it
Authors: Kinzey Bertram Y.
Published: October 2013

Organists and organ builders desire long reverberation times for their instruments. A simple statement of a time is an inadequate specification for the acoustic response of a venue intended for medium to larger organs. An important added specification requirement is that the reverberation decay curve be steep at first and be much less so later if satisfactory clarity is to be achieved. Data is presented to illustrate and establish this criterion. Research is cited to demonstrate how the double slope reverberation decay can be achieved by the use of coupled spaces adjacent to a main performing room. Data is given to demonstrate how some symphony halls have realized the use of this technique.
Localization of killer whale (Orcinus orca) vocalizations using a triangular hydrophone array in Johnstone Strait, British Columbia, Canada
Authors: Grebner Dawn M. , Bradley David L. , Capone Dean E.
Published: October 2013

A triangular hydrophone array was bottom-mounted in Johnstone Strait, in summer 2006, to localize sounds emitted by individual or small groups of orcas. Spatial and temporal positioning of individual orcas was obtained from a cliff-site observation platform; a video camera recorded surface behaviors and associations while a theodolite was used to obtain vertical and azimuthal angles needed to calculate distances to the animals. The time of arrival differences of the orca sounds at each hydrophone was used to determine the angle of arrival of the sound. Sounds were then aligned in time and space with the orcas’ corresponding movement tracks. The ability to spatially and temporally localize the vocalizations and behaviors of an isolated orca provides insight into how an individual or group of individuals may function within a matrilineal unit or pod. The objective of this study is to determine if there are defined ‘‘roles’’ in the vocal behaviors of individuals (adult males, adult females, juveniles, calves) within small groups of orcas; specifically, individual differences in orca calling behavior that regulates group movement and changes in group behavior. Results from analysis of pod encounters will be discussed and correlation of vocalizations and specific individual behavior addressed.
Improving tissue-type imaging of prostate cancer by combining magnetic-resonance spectroscopy and ultrasound spectral parameters
Authors: Feleppa Ernest , Dasgupta Shreedevi , Ramachandran Sarayu , Kalisz Andrew , Porter Christopher , Lacrampe Marc , Isacson Christina
Published: October 2013

This study aims to improve existing prostate tissue-type imaging methods by utilizing independent tissue properties sensed by MR and US. An artificial-neural-network classifier was trained using the blood PSA level and ultrasonic spectral parameters of echo signals derived from biopsied regions of 64 patients. Biopsy-core histology was used as the gold standard. Classifier performance was assessed using ROC analysis. We generated tissue-type images (TTIs) using a look-up table that returned cancer-likelihood scores for spectral parameter and PSA combinations. We assessed the feasibility of integrating MR and US parameters to improve classification. 3-D renderings of the prostate from transverse MR and US scans were generated from data acquired preoperatively. The 3-D rendering obtained from MR data showed that the prostate was considerably distorted (flattened) by the large MR endorectal probe compared to the distortion caused by the smaller US endorectal probe. The MR 3-D rendering was warped successfully to match the US volume. Warping successfully compensated for the deformations introduced during scanning. This suggests that accurate coregistration of 3-D data acquired using MR and US is possible. Such coregistration is essential for developing an improved classifier based on MR and US parameters.
Angular dependence of target strength for simple geometric shapes
Authors: Tucholski Edward
Published: October 2013

Understanding the active sonar equation is a fundamental skill for a course in underwater acoustics and sonar such as that taught at the United States Naval Academy. Students must develop an intuitive understanding of each term in both the noise-limited and reverberation-limited cases. In this demonstration, the angular dependence of the target strength term is explored using commercially available 25- and 40-kHz airborne piezoelectric transducer/receiver pairs. By rotating standard target shapes (e.g., rectangular plates, circular plates, finite cylinders, ellipsoids), reflected intensity is measured as a function of angle of rotation. The measured data are compared with those predicted by standard theoretical predictions. While the same measurements could be made in a tank using submerged transducers, the airborne transducers offer the advantage of lower cost and simplicity of apparatus. Additionally, unwanted modal interference from sound reflection off tank surfaces is reduced in the airborne measurement. By direct observation, future naval officers are able to study target strength so as to understand how to position their sensors to optimize their own active sonar performance and position their warship to minimize detection by enemy active sonar.
Development of the first audio microphone for use on the surface of Mars
Authors: Delory Gregory T. , Luhmann Janet , Friedman Louis , Betts Bruce
Published: October 2013

In 1999, NASA launched the Mars Polar Lander (MPL) to study volatiles and the climate history of Mars. Among the many instruments aboard the spacecraft was the first audio microphone sensor ever developed for the environment of Mars, included as a piggy-back sensor on the Russian LIDAR experiment. Funded by The Planetary Society and built and tested by the U.C. Berkeley Space Sciences Laboratory, the Mars Microphone was a unique and powerful tool for public engagement with the Mars exploration program. The possibilities for sound sources on Mars included wind and dust found in dust devils and storms, atmospheric electricity, and lander-generated sounds such as camera movements and the digging of the robotic arm. Here we outline the design, development, and test program for a spaceflight acoustic sensor, where the unique challenges of extreme environments, limited data bandwidth, and requirements for a low-power, light-weight system were overcome. While the MPL mission was lost and no data ever returned, the Mars Microphone nonetheless stimulated interest in the science of extra-terrestrial acoustics and in future planetary mission instruments based on acoustic methods.
Selective spatial attention in a dynamic cocktail party task: Evidence for a strategy based on masker minimization
Authors: Brungart Douglas , Iyer Nandini , Simpson Brian
Published: October 2013

In cocktail-party listening tasks with multiple spatially separated talkers, it is not clear whether the performance advantages of spatial separation are the result of a target-max strategy, where the listener uses selective attention to enhance sensitivity at the location of the target, or a masker-min strategy, where the listener selectively suppresses sensitivity at the locations of the maskers. In this experiment, listeners were asked to attend to a randomly moving CRM target phrase that was masked by two independently moving CRM masking phrases. The competing signals were lateralized solely on the basis of ITD, and they were band-pass filtered into non-overlapping bands to minimize the effects of energetic masking. The results of the experiments showed (1) that listeners were much more sensitive to changes in the masker locations than to changes in the target location; (2) that listeners consistently performed worse when the two maskers were spatially separated than when they were co-located, even when the average separation between the target and the maskers increased; and (3) that spatial separation of the second masker provided almost no benefit when the first masker was co-located with the target speech. These results seem to provide general support for the masker-min theory of auditory spatial attention.
In situ reflection coefficient measurements from 5–50 kHz from the experiments for validation of acoustic modeling techniques (EVA) sea test
Authors: Isakson Marcia , Chotiros Nicholas , Piper James , Zampolli Mario
Published: October 2013

An accurate model of high-frequency reflection loss at the ocean bottom is critical to understanding shallow water sound propagation and the detection and classification of buried objects such as mines. The value of the observed reflection coefficient can be perturbed by such effects as scattering from a rough interface and dispersion in the ocean sediment. To obtain ground truth measurements for model development and verification, reflection coefficients from a rough water/sediment interface were measured as part of the experiments for validation of acoustic modeling techniques (EVA) sea test on the north shore of Isola dElba, Italy. Data at grazing angles from 10–80 deg and frequencies from 5–50 kHz were obtained. Experimental effects such as transducer response and spherical wave effects were quantified. The data will be analyzed to determine the influence of dispersion and scattering effects. [Work supported by ONR, Ocean Acoustics.]
Rehabilitating the world’s worst sounds: Time-frequency reassignment in sound modeling and morphing
Authors: Fitz Kelly
Published: October 2013

Sound morphing implies a gradual transformation from one sound to another, or the transfer of features of one sound to another. Morphing has been used to synthesize the voices of aliens and animals and a wide variety of sound effects in films and popular music. Additive sound models provide a flexible medium for performing sound morphing and manipulation. The application of time-frequency reassignment—the computation of precise, signal-dependent loci for time-frequency analysis data from first-order partial derivatives of short-time spectral phase—to the construction of robust, manipulable additive sound models will be discussed, and the advantages afforded by the increased precision of reassigned sound models will be demonstrated. Machines, mammals, and musical instruments will be morphed and manipulated, and an attempt will be made to rehabilitate the very worst sounds in the world.