bluuebunny/crossref_metadata_2025 huggingface dataset:
Air acoustic propagation in a multiple scattering environment: Application to target detection in a forest
Authors: Higley W. J. , Roux Philippe , Sarkar Jit , Kuperman W. A.
Published: September 2013

A small-scale acoustic experiment in a multiple scattering medium has been conducted in the audible bandwidth of 4 to 6 kHz. Approximately 200 1-m-long PVC pipes were stood upright in a 8×10 m square between an array of eight microphones and a parallel array of ten speakers to simulate conditions in a dense forest. The Green’s functions of the propagation between each microphone and speaker were measured several times with no changes to the medium. Then, an additional, moving scatterer was introduced into the medium and the Green’s functions were again acquired. An algorithm has been developed to recognize the difference in the propagation when the additional scatterer is present and when it is not. Further analysis of this data shows the effective cross-section of the additional scatterer. A potential use of such an algorithm and system is the detection and classification of foreign scatterers in a forest.
Multiple Bragg scattering in arbitrary periodic acoustic waveguides
Authors: Valente Dan , Swanson David C.
Published: September 2013

Periodic acoustic waveguides allow the propagation of only certain bands of frequencies, thus making them very effective acoustic filters. The particular distribution of these bands depends critically on the waveguide geometry. If the variation of the waveguide walls happens to be sinusoidal, then the waveguide preferentially reflects only the frequency which matches the Bragg condition for complete backscatter. The reflection of a single frequency in the sinusoidal waveguide seems to contrast the case of a more general periodic structure, where numerous bands of frequencies are disallowed. In this work, the relationship between the sinusoidal waveguide and an arbitrary periodic waveguide is studied using a transmission line model. Inspection of the input reflection coefficient as a function of frequency yields striking similarities to the Fourier transform of the wall variation, implying that a waveguide whose walls are defined by an arbitrary periodic function independently Bragg reflects the individual Fourier components of the wall variation function. The specific example of a waveguide with a square wave variation (a waveguide with periodic expansion chambers) will be discussed and compared to the literature, as well as the possibilities of recovering the waveguide geometry from the input reflection coefficient.
Scattering of two-dimensional periodic gratings composed of cylindrical cavities in an elastic medium
Authors: Robert Sebastien , Franklin Hervé , Conoir Jean-Marc
Published: September 2013

A theoretical and a numerical calculation of the scattering by a two-dimensional periodic grating composed of parallel cylindrical cavities embedded in an elastic medium are presented. The major point of the method is that the whole grating can be decomposed as a series of a finite or an infinite number of infinite rows of periodically spaced identical cavities. The scattering by each row is determined by an exact self-consistent multiple scattering calculation developed in the elastic case. The propagation of the waves from row to row can then be determined by an iterative method or from Bloch’s theorem. Compared to previous works on gratings of elastic scatterers in a fluid, this study emphasizes new and interesting results. Among them are the systematic formation of new stopping and passing bands when the scattering is resonant, and the presence of frequency domains of higher coupling between the longitudinal and transverse waves, corresponding to the propagation of guided waves between two reticular planes of the grating. Examples of gratings with only one periodicity direction are also studied.
Backscattering in space- and time-dependent random media acoustic intensity fluctuations
Authors: Frankenthal Shimshon , Beran Mark J.
Published: September 2013

In two recent publications [(1) S. Frankenthal and M. J. Beran, Waves Random Media 13, 241–268 (2003); (2) A. M. Whitman, M. J. Beran, and S. Frankenthal, ibid. 13, 269–286 (2003)], an incremental slab formulation was employed to derive the equations for the intensity of acoustic signals that undergo scattering in a medium whose sound speed fluctuates randomly both in space and time. These equations were used to track the propagation of a narrow-band pulse and its echoes across a one-dimensionally stratified slab, and to compute the effects of intermodal scattering on the modal intensities along a sinusoidally excited duct. Here, following a brief review of the main assumptions and the major features of the intensity equations, the same formulation is used to derive equations for the mean-square intensity, which is needed to calculate the intensity fluctuations. With sinusoidal excitation, an analytical solution of these equations is obtained for propagation across a one-dimensionally stratified slab, and a system of differential equations, which can be solved by the techniques used in Ref. 2, is derived for the modal mean square intensities in a duct.
The phase gradient method (PGM) applied to a monoclinic plate immersed in water
Authors: Guénégou Lionel , Lenoir Olivier
Published: September 2013

For a water-loaded isotropic plate, the PGM deals with the study of the partial derivatives of the phase of its reflection coefficient. The phase derivatives with respect to the frequency f, to the bulk phase velocities of the pressure (cP) and shear (cS) waves propagating in the plate, to the phase velocity cF of the waves in water, and to the incident angle are investigated. The frequency and angular derivatives permit characterization of the frequency and angular resonances of the plate (locations and widths) without calculations in the associated complex planes. The derivatives with respect to cP,S give the prevailing polarization state of the Lamb waves. For a monoclinic plate (orthotropic plate where the incident plane is different from a symmetry plane), at a given incident angle, three phase velocities in the plate are to be considered. The additional one with regard to the isotropic case is the quasi-SH wave phase velocity. It is shown in this study that the frequency phase derivative study is still convenient to obtain the frequency resonance features, and that the phase derivatives with regard to the three velocities indicate whether a guided wave is mainly a quasilongitudinal, quasishear, or quasi-SH mode.
Flow noise and rapidly distorting turbulence in shear layers
Authors: Martinez R.
Published: September 2013

Rapid distortion theory (RDT) is a linear analytical framework for the formal split of a flow’s hydrodynamic sources from their acoustic effects. The former include time-varying vorticity, turbulence, and unsteady heat injection. Their acoustic effects manifest themselves through a generalized wave-propagation operator in the consistently separated equations of fluid mechanics. The present development reports on progress in extending RDT to include mean shear and associated macro-vorticity in the static but spatially nonuniform carrier flow. The analysis begins by fully recasting standard RDT [Goldstein, JFM (1978)] for irrotational backgrounds in tensor-dyadic form for the curvilinear coordinates of the streamlines of the background flow. This complete geometrization of the background offers clues for achieving a similar split in the time-varying acoustical and turbulent variables that perturb the more general sheared freestream. The new development could eventually be applied to turbulent boundary layers, and particularly to spatial discontinuities such as steps and gaps that (rapidly) distort the statistics of the perturbed rotational flow and thereby lead to additional broadband noise via RDT’s generalized wave-equation operator and geometrized source terms.
Understanding response proclivity and the limits of sensory capability: What do we hear and what can we hear?
Authors: Leek Marjorie R. , Neff Donna L.
Published: September 2013

Charles Watson’s studies of informational masking and the effects of stimulus uncertainty on auditory perception have had a profound impact on auditory research. His series of seminal studies in the mid-1970s on the detection and discrimination of target sounds in sequences of brief tones with uncertain properties addresses the fundamental problem of extracting target signals from background sounds. As conceptualized by Chuck and others, informational masking results from more central (even ‘‘cogneetive’’) processes as a consequence of stimulus uncertainty, and can be distinguished from ‘‘energetic’’ masking, which primarily arises from the auditory periphery. Informational masking techniques are now in common use to study the detection, discrimination, and recognition of complex sounds, the capacity of auditory memory and aspects of auditory selective attention, the often large effects of training to reduce detrimental effects of uncertainty, and the perceptual segregation of target sounds from irrelevant context sounds. This paper will present an overview of past and current research on informational masking, and show how Chuck’s work has been expanded in several directions by other scientists to include the effects of informational masking on speech perception and on perception by listeners with hearing impairment. [Work supported by NIDCD.]
Selective auditory attention to features of complex sounds: A comparative approach
Authors: Mercado Eduardo , Orduña Itzel
Published: September 2013

When listeners are trained to respond based on one spectrotemporal component of a complex sound, enhanced processing of the behaviorally relevant feature provides an objective correlate of selective attention [I. J. Hirsh and C. S. Watson, Annu. Rev. Psychol. 47, 461–484 (1996)]. To study this issue in a nonhuman species, rats were trained to classify multidimensional acoustic stimuli based on the rate, direction, and range of frequency modulation. Rats successfully learned to classify complex sounds along the dimensions of rate and direction of frequency modulation, but not based on the range of frequency modulation. Rats classified stimuli most accurately when the relevant dimension was rate of frequency modulation. The relative ease with which rats learn to classify complex sounds along a particular dimension can be predicted based on how auditory cortical neurons in rats respond to such sounds. These findings provide new insights into how neural processing may constrain selective auditory attention to features of complex sounds. [Work supported by NIH.]
Listening weights for signals and maskers with uncertain frequency in normal-hearing and hearing-impaired listeners
Authors: Alexander Joshua M. , Lutfi Robert A.
Published: September 2013

The effect of signal and masker uncertainty on listener decision weights was measured in 12 normal-hearing (NH) and 6 hearing-impaired (HI) listeners. The signal was a tone of 0.8, 2.0, or 5.0 kHz. The maskers were fixed-frequency tones separated from the signal(s) by two-third octaves and played simultaneously with the signal(s). Each masker tone had an independent probability of occurrence of 0.5 on each trial. In the signal-uncertain (SU) condition one of the three signals was played at random with equal probability on each trial. In the signal-certain (SC) condition the signal frequency was constant on each trial. In each condition the relative influence of each signal and masker frequency on listener decisions was estimated from regression weights relating listener responses to the presence or absence of each tone on every trial. For SC, the results indicate that NH and HI listeners put significantly greater weight on the signal frequencies than the masker frequencies. For SU, however, HI listeners tended to weight a narrower spectral region compared to NH listeners. It is concluded that HI listeners are able to selectively attend to an individual signal better than they can divide their attention among multiple signals. [Work supported by NIDCD.]
Informational masking of speech-analog signals: Independence of prosodic-rhythmic and formant trajectory cues
Authors: Divenyi Pierre
Published: September 2013

One factor of poor speech understanding in cocktail-party settings is masking of information in a target stream by similar concurrent information in an interfering background stream. To overcome this deficit, the information in the two streams must be different along at least some acoustic dimensions. The present study investigated whether informational differences along various dimensions between a speech-analog target and an interfering distractor stream were processed independently from one another, or whether dividing one’s attention between the dimensions affects performance. In a single-interval, forced-choice experiment, listeners had to discriminate the rhythmic pattern of a burst triplet (AM) or an up–down/down–up 150-ms single-formant transition pattern (FM), or both, imposed on a 500-ms harmonic complex carrier, embedded in a distractor stream of random AM bursts, or constant single-formant up–down FM started in a random transition phase, or both. Fundamental frequencies of target and distractor were different. Results indicate that, when compared to discrimination of either the AM or the FM pattern alone, simultaneous discrimination of the AM and FM patterns did not result in a loss, suggesting that informational masking may operate independently on different dimensions. [Research supported by Grant R01-AG07998 from National Institute on Aging and by the VA Medical Research.]
Visualization of the energy flow for guided forward and backward waves in and around a fluid-loaded elastic cylindrical shell via the Poynting vector field
Authors: Dean Cleon E. , Braselton James P.
Published: September 2013

Color-coded and vector-arrow grid representations of the Poynting vector field are used to show the energy flow in and around a fluid-loaded elastic cylindrical shell for both forward- and backward-propagating waves. The present work uses a method adapted from a simpler technique due to Kaduchak and Marston [G. Kaduchak and P. L. Marston, ‘‘Traveling-wave decomposition of surface displacements associated with scattering by a cylindrical shell: Numerical evaluation displaying guided forward and backward wave properties,’’ J. Acoust. Soc. Am. 98, 3501–3507 (1995)] to isolate unidirectional energy flows.
Error analysis and implementation issues for energy density probe
Authors: Locey Lance L. , Woolford Brady L. , Sommerfeldt Scott D. , Blotter Jonathan D.
Published: September 2013

Previous research has demonstrated the utility of acoustic energy density measurements as a means to gain a greater understanding of acoustic fields. Three spherical energy density probe designs are under development. The first probe design has three orthogonal pairs of surface mounted microphones. The second probe design utilizes a similarly sized sphere with four surface mounted microphones. The four microphones are located at the origin and unit vectors of a Cartesian coordinate system, where the origin and the tips of the three unit vectors all lie on the surface of the sphere. The third probe design consists of a similarly sized sphere, again with four surface microphones, each placed at the vertices of a regular tetrahedron. The sensing elements of all three probes are Panasonic electret microphones. The work presented here will expand on previously reported work, and address bias errors, spherical scattering effects, and practical implementation issues. [Work supported by NASA.]
The application of acoustical methods of ply separation detection in plates
Authors: Iwaniec Marek
Published: September 2013

The author applied modal analysis and energy flow methods for detection of multilayer plate delaminating. New design of hardware for field measurements especially for conservation of monuments of history was developed. The author also tested two new noninvasive measurement methods. The first one is based on measurement of electric field dynamic parameters in the vicinity of subsurface delaminating and the second on the measurement of the frequency response of a structure being excited by the diffusive acoustic near field of the radiator. Main application of developed devices was use in a wide band of practical applications in detection of delaminating of precious wall paintings—frescoes. Preliminary tests at laboratory conditions were carried out with designed devices on fresco samples prepared due to old technologies. Results proved satisfactory sensitivity of the devices for practical application to conservator team works. The assessment of a structure technical state is performed on the basis of real-time calculations of the quality measures and damage probability. The proposed device enables the investigator to identify fresco delaminating of 8-cm diameter located at a depth of 5 mm. Discussed methods can be useful in diagnostics of many other multilayer structures.
A decentralized algorithm for acoustic localization using a distributed sensor network
Authors: Schmidt Peter L. , Amundson Isaac , Frampton Kenneth D.
Published: September 2013

An acoustic source localization algorithm has been developed for use with large-scale sensor networks using a decentralized computing approach. This algorithm, based on a time delay of arrival (TDOA) method, uses information from the minimum number of sensors necessary for an exactly determined solution. Since the algorithm is designed to run on computational devices with limited memory and speed, the complexity of the computations has been intentionally limited. The sensor network consists of an array of battery-operated COTS Ethernet-ready embedded systems with an integrated microphone as a sensor. All solutions are calculated as distinct values, and the same TDOA method used for solution is applied for ranking the accuracy of an individual solution. Repeated for all combinations of sensor nodes, solutions with accuracy equivalent to complex array calculations are obtainable. Effects of sensor placement uncertainty and multipath propagation are quantified and analyzed, and a comparison to results obtained in the field with a large array with a centralized computing capability using a complex, memory intensive algorithm is included.
Noise reduction using a multimicrophone array for automatic speech recognition on a handheld computer
Authors: Shaw Scott T. , LaRow Andrew J. , Schoenborn William E. , Rodriguez Jason , Gibian Gary L.
Published: September 2013

A four-microphone array and signal-processing card have been integrated with a handheld computer such that the integrated device can be carried in and operated with one hand. Automatic speech recognition (ASR) was added to the USAMRMC/TATRCs Battlefield Medical Information System (BMIST) software using an approach that does not require modifying the original code, to produce a Speech-Capable Personal Digital Assistant (SCPDA). Noise reduction was added to allow operation in noisier environments, using the previously reported Hybrid Adaptive Beamformer (HAB) algorithm. Tests demonstrated benefits of the array over the HP/COMPAQ-iPAQ built-in shielded microphone for noise reduction and automatic speech recognition. In electroacoustic and human testing including voice control and voice annotation, the array provided substantial benefit over the built-in microphone. The benefit varied from about 5 dB (worst-case scenario, diffuse noise) to about 20 dB (best-case scenario, directional noise). Future work is expected to produce more rugged SCPDA prototypes for user evaluations, revise the design based on user feedback and real-world testing, and possibly to allow hands-free use by using ASR to replace the push-to-talk switch, providing feedback aurally and/or via a head-up display. [Work supported by the U.S. Army Medical Research and Materiel Command (USAMRMC), Contract No. DAMD17-02-C-0112.]
Approaches to accelerate three-dimensional acoustic propagation models
Authors: Arvelo Juan , Rosenberg Allan
Published: September 2013

A three-dimensional split-step Pade parabolic-equation approach [J. Comput. Acoust. 9(2), 17–39 (2001)] was developed as an extension to Collins and Chin-Bings algorithm [J. Acoust. Soc. Am. 87, 1104–1109 (1990)] to account for azimuthal acoustic refraction via a narrow-angle approximation. It was shown that high accuracy requires fine azimuthal and range step sizes. Therefore, a couple of Pade terms are sufficient given the required small range step size. The paper also mentions the possible implementation of a variable azimuthal grid size, where the number of azimuthal segments increases proportionally with increasing range, as another approach to boost the models computational speed. In this talk, we investigate the possibility of azimuthal padding as another approach to speed-up the model when the user is only interested in propagating the acoustic field along a wedge of azimuthal angles instead of the entire 360.
Progress in hybrid finite-element/propagation tool modeling of scattering from objects in underwater waveguides
Authors: Zampolli Mario , Burnett David S. , Jensen Finn B. , Tesei Alessandra , Schmidt Henrik , Blottman John B.
Published: September 2013

A steady-state 3D finite-element software called FESTA (Finite-Element STructural Acoustics), is being developed at the NATO Undersea Research Centre. The code is geared towards a variety of applications in underwater acoustics, such as multistatic scattering from localized inhomogeneities, scattering across interfaces between fluids and/or solids, and multistatic scattering from single and multiple fluid-loaded elastic targets. One issue of importance to researchers in underwater acoustics is the trade-off between full 3D models and thin-shell theory. To address this issue, FESTA results are compared to results from thin-shell scattering codes for cylindrical bodies with spherical endcaps. Another part of the work focuses on the integration of the finite-element tool with underwater propagation tools for the computation of multistatic scattering from targets buried, partially buried or proud inside shallow-water waveguides. To achieve this, FESTA is coupled to the MIT underwater propagation tool OASES. One method of interfacing FESTA to OASES is based on an environment-independent characterization of the target via in vacuo response matrices. Recent results from response matrix computations are presented and trade-offs of this method are discussed.
Multiple uncorrelated scattering effects in waveguide propagation
Authors: Tracey Brian H.
Published: September 2013

First-order perturbation theory has been widely used to model scattering from surface roughness in ocean waveguides. After sound is initially scattered it will propagate further and may rescatter from the rough surface. This rescattering effect is not captured by first-order perturbation theory. Voronovich [Wave Scattering from Rough Surfaces (Springer-Verlag, New York, 1994)] has argued that the scattered energy will return to the rough interface at range intervals that are large compared to the correlation length of the roughness. Thus the different scattering events can be treated as uncorrelated and a single-scattering theory can be used to describe each event. In this paper an existing normal mode scattering theory is modified to include this extension to uncorrelated rescattering. Numerical examples for low frequencies in shallow water are used to understand how the importance of the rescattering depends on seabed type. Rescattering was not found be significant for sandy bottoms, but is predicted to become more important as the bottom compressional speed increases and more scattered energy is trapped in the waveguide. [Work sponsored by DARPA-ATO under Air Force Contract F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Government.]
Variation of the acoustic directivity pattern due to inhomogeneous objects in the region of nonlinear interaction
Authors: Zagrai Nikolai
Published: September 2013

The homogeneity of the physical medium can be investigated using nonlinear interaction of the acoustic waves. The proposed approach utilizes the fact that the secondary acoustic field is dependent on configuration of the region of nonlinear interaction (RNI), inhomogeneity of its physical properties and the transmitting signals of the primary acoustic field. Therefore, by studying a directivity pattern of the secondary acoustic field at combination frequencies it is possible to determine a number and location of the inhomogeneous objects in the RNI. The axial position and transverse dimensions of the objects affect the directivity pattern measured in the far field. In the case of the axially symmetric RNI, displacement of an object leads to the asymmetry of the directivity pattern and can be easily estimated. The model is proposed to account for the respective effect of the objects size, degree of asymmetry, and dynamics of the directivity pattern at the combination frequencies. The developed approach suggests that the methods of nonlinear acoustics can be effectively used for physical diagnostics and condition monitoring.
Investigation on the flanking transmission of impact sound insulation of floor
Authors: Semprini Giovanni , Cocchi Alessandro
Published: September 2013

Impact sound pressure level of floors depends, as general rule, on direct sound radiated by the floor excited by a standard tapping machine and on flanking transmission of lateral walls. Depending on the kind of junction between the floor and walls of the receiving room, flanking paths can be more or less important. Requirements of laboratory test specimens are not well specified in EN ISO 140 standards, particularly for junctions of the test floor and lateral walls. In this paper measurements performed at DIENCA laboratory are presented in order to evaluate the influence of flanking transmission on impact sound pressure levels of a standard floor and on impact sound reduction level of standard floor with a resilient layer. Measurements are performed on a 14-cm-thick concrete floor in two different conditions: first connected on two sides of the receiving room and then on all four sides. Impact sound pressure levels and vibration levels are analyzed in order to evaluate the contribution of different transmission paths. As the measurements were carried on in the new facility for measurement of the contribution of the flanking transmission, this facility will be exhaustively presented in the paper.
A nonlinear model-based acoustic inversion to estimate the abundance and biomass distributions of marine organisms
Authors: Chu Dezhang , Wiebe Peter
Published: September 2013

Multi-frequency and/or broadband acoustic systems can be used to estimate the abundance and biomass distributions of marine organisms with inversion techniques [Holliday et al., J. Cons. Int. Explor. Mer. 46, 52–67 (1989)]. The linear inversion scheme is commonly used in fisheries and zooplankton acoustics and is based mostly on relatively simple scattering models. A more advanced nonlinear inversion method is presented in this talk. It uses the more sophisticated scattering models and the material properties measured in situ to estimate the abundance and biomass of marine organisms. A multi-frequency acoustic data set collected with the bio-optical multi-frequency acoustical and physical environmental recorder (BIOMAPER-II) during the austral fall Southern Ocean GLOBEC broad-scale cruise in 2002 was used in the inversion. At the depth where the Antarctic krill (Euphausia superba) were the dominate scatterers, the behavioral information of the animal such as mean angle of orientation and the standard deviation of the tilt angle were estimated with the nonlinear inversion. Furthermore, nonuniqueness and uncertainty inherently associated with the nonlinear inversion are analyzed. [Work supported by the NSF.]
The Bergen multifrequency analyzer (BMA): A new toolbox for acoustic categorization and species identification
Authors: Ona Egil , Korneliussen Rolf , Knudsen Hans Petter , Rang Kjell , Eliassen Inge , Heggelund Yngve , Patel Daniel
Published: September 2013

Multifrequency split-beam echo sounders with nearly identical and overlapping acoustic beams have been regularly used in acoustic surveys for fish stock abundance estimation. Calibrated raw data from up to six simultaneously working echo sounders at 18, 38, 70, 120, 200, and 364 kHz were applied for developing a new processing tool for real-time acoustic target categorization and acoustic species identification. The system now handles raw data from the Simrad EK500 and EK60 split-beam echo sounders, and performs a stepwise, modular sequence of analysis, like bottom detection, noise quantification and removal, target categorization, and school detection in near-real time. Direct generation of new, synthetic echograms, based upon the measured frequency response of the targets, is also one of the most useful features of the system. This information may significantly increase the accuracy of acoustic survey estimates of fish and zooplankton. New routines for noise removal, target categorization, and school detection will be presented, as well as new methods for training and building the artificial experience of the analyzer.
Acquisition of transcranial ultrasonic signals from adult subject’s applications to the detection of brain injury
Authors: Mobley Joel , Vo-Dinh Tuan , Daley Brian J. , Holland Martin C.
Published: September 2013

In the clinical setting, several technologies (e.g., x-ray CT, MRI, color-duplex ultrasonography) can provide doctors with noninvasive windows through the cranium into the brain. In the field, however, there is a need for a portable device that can noninvasively detect brain injuries at the scene of a trauma, providing first responders with urgent diagnostic information in the critical first hour postincident. Such an instrument should be simple to operate and must supply results that are straightforward to interpret. This work is part of an effort to devise ultrasonic methods that can serve as the operating principle for such a device. In this talk, human studies are described in which backscattered ultrasound data were obtained transcranially from adult volunteers. The ultrasound signals, acquired with single transducers in pulse–echo mode, are interpreted anatomically with the aid of a multilayer model of the propagation path. Through the model, the complex structures of the echo patterns are revealed and the important roles of the scalp and skull layers are made evident. The ultrasound data are further analyzed to assess the suitability of these signals for implementing a tissue characterization approach to the injury detection problem.
Importance of ka-range on the simultaneous estimation of scatterer size and total attenuation from ultrasound backscattered waveforms
Authors: Bigelow Timothy A. , O’Brien William D.
Published: September 2013

Considerable effort has been directed to diagnosing the malignancy of solid tumors noninvasively by determining a scatterer size from a statistical analysis of the ultrasound-backscattered waveforms. In vivo tumor assessments have had limited success due to frequency-dependent attenuation along the propagation path masking the frequency dependence of the scatterer size. In this study, both attenuation and size were solved simultaneously by a two-parameter minimization of the mean squared error between a reference spectrum, modified by the attenuation and scatterer size, and the backscattered waveforms. The performance of the approach was assessed by simulations of a homogeneous region containing scatterers with a Gaussian impedance distribution. The simulations varied the effective radius of the scatterers (5 to 150 mm), the attenuation of the region (0 to 1 dB/cm/MHz), and the bandwidth of the source. In all cases, comparable accuracy and precision of the scatterer size were obtained whenever the range of ka values (wavenumber times effective radius) had the same width (largest ka minus smallest ka). The precision and accuracy improved with increasing width. A width of 1 gave an accuracy/precision of ∼15%±35% whereas a width of 1.5 gave an accuracy/precision of ∼5%±15%. [Work supported by a Beckman Institute Fellowship.]
Scatterer size and concentration estimation technique based on a 3D acoustic impedance map from histologic sections
Authors: Mamou Jonathan , Oelze Michael L. , O’Brien William D. , Zachary James F.
Published: September 2013

Accurate estimates of scatterer parameters (size and acoustic concentration) are beneficial adjuncts to characterize disease from ultrasonic backscatterer measurements. An estimation technique was developed to obtain parameter estimates from the Fourier transform of the spatial autocorrelation function (SAF). A 3D impedance map (3DZM) is used to obtain the SAF of tissue. 3DZMs are obtained by aligning digitized light microscope images from histologic preparations of tissue. Estimates were obtained for simulated 3DZMs containing spherical scatterers randomly located: relative errors were less than 3%. Estimates were also obtained from a rat fibroadenoma and a 4T1 mouse mammary tumor (MMT). Tissues were fixed (10% neutral-buffered formalin), embedded in paraffin, serially sectioned and stained with H&E. 3DZM results were compared to estimates obtained independently against ultrasonic backscatter measurements. For the fibroadenoma and MMT, average scatterer diameters were 91 and 31.5 μm, respectively. Ultrasonic measurements yielded average scatterer diameters of 105 and 30 μm, respectively. The 3DZM estimation scheme showed results similar to those obtained by the independent ultrasonic measurements. The 3D impedance maps show promise as a powerful tool to characterize ultrasonic scattering sites of tissue. [Work supported by the University of Illinois Research Board.]
Ultrasonic tissue characterization for the classification of prostate tissue
Authors: Scheipers Ulrich , Ermert Helmut , Koenig Katharina , Sommerfeld Hans-Joerg , Garcia-Schuermann Miguel , Senge Theodor , Philippou Stathis
Published: September 2013

Radio-frequency ultrasound echo data of the prostate are captured during routine examinations with standard ultrasound equipment. The data are directly transmitted to a PC and subdivided into numerous regions of interest. Several parameters describing the histological characteristics of the underlying tissue are calculated from the frequency spectrum and from the demodulated signal of the underlying echo data. Parameters are fed into two adaptive network-based fuzzy inference systems working in parallel. One system is used to classify hypo- and hyperechoic tumors, the other system is used to detect isoechoic tumors within the normal prostate tissue. Subsequent morphological analysis combines clusters to mark areas of similar tissue characteristics. Classification results are presented as two-dimensional malignancy maps and as volumetric reconstructions of the whole organ. Radio-frequency ultrasonic echo data of 100 patients have been recorded. Tissue samples following radical prostatectomies are used as the gold standard. The area under the ROC curve is A=0.86±0.01 for hypo- and hyperechoic tumors and A=0.84±0.02 for isoechoic tumors using leave-one-out cross validation over patient datasets.
A comparison study in cell transfection: Which one is better, sonoporation versus electroporation?
Authors: Wu Junru , Pepe Jason , Rincon Mercedes
Published: September 2013

An experimental study has been performed for cell suspensions to compare efficiency of cell transfection, which is the process of introducing recombinant DNA into eukaryotic cells (eukaryotic cells have chromosomes with nucleosomal structure) and subsequently integrating that DNA into the recipient cell’s chromosomal DNA. It was demonstrated that electroporation was superior to sonoporation in terms of viability (65.8 2.3% vs. 50.8 4.15%) and transfection efficiency (15.83 3.5% vs. 7.53 0.4%) for Jurkat lymphocytes (nonprimary cells), and sonoporation was better in terms of viability (64.8 1.51% vs. 53.7 1.53 %) and transfection efficiency (2.73 0.21% vs. 0.43 0.06%) for human peripheral blood mononuclear cells (primary cells). The electroporation was performed using a Gene Pulser II Apparatus with voltage of 250 V, and the sonoporation was achieved using 2-MHz pulsed ultrasound exposure (ISPPA=80 W/cm2) assisted with encapsulated bubbles (Optison).
Approaches to simulate electromechanical coupling in voided piezoelectric materials
Authors: Arvelo Juan , Busch-Vishniac Ilene
Published: September 2013

Recent work has demonstrated piezoelectric behavior in voided polymers. It is thought that the piezoelectricity results from the creation of space charges bordering the voids when the material is exposed to an electric field in excess of the breakdown strength. The resulting voided piezoelectric material is more flexible than conventional piezoelectric ceramics, and may be far less expensive to manufacture. Accurate models of piezoelectricity in voided materials are needed to explore the limits of performance and their use under a wide range of conditions. We are using finite element analysis to develop a model of the mechanical, electrical, and piezoelectric behavior in voided materials. Results for some of the materials of current interest, such as low-density polypropylene (LDPP) and porous polytetrafluoroethylene (PTFE) will be presented. [Work performed under a JHU/APL sabbatical to the JHU/WSE.]
Simulation of linear aeracoustic propagation in lined ducts with discontinuous Galerkin method
Authors: Peyret Christophe , Delorme Philippe
Published: September 2013

The simulation of the acoustic propagation inside a lined duct with nonuniform flow still presents problems when geometry is complex. To handle computations on a complex geometry, without consequential effort, unstructured meshes are required. Assuming irrotational flow and acoustic perturbation, a well-posed finite element method based on the potential equation is established. But, the effect of the thin boundary layer is then neglected, which is not relevant to the acoustical processes occurring near the lining. Recent works have focused on the tremendous interest of the Galerkin discontinuous method (GDM) to solve Euler’s linearized equations. The GDM can handle computations on unstructured meshes and introduces low numerical dissipation. Very recent mathematical works have established, for the GDM, a well-posed boundary condition to simulate the lining effect. Results computed with the GDM are presented for a uniform cross section lined duct with a shear flow and are found to be in good agreement with the modal analysis results, thereby validating the boundary condition. To illustrate the flexibility of the method other applications dealing with instabilities, air-wing diffraction, and atmospheric propagation are also presented.
Engineering acoustic lenses with help from evolution
Authors: Håkansson Andreas , Sánchez-Dehesa José , Sánchis Lorenzo
Published: September 2013

Optimization engineering through evolutionary algorithms have proven to be very efficient, especially in hard problems containing a large set of optimization parameters. Like evolution this family of algorithms is able to tackle enormous complex problems with fairly simple means. Here, a simple genetic algorithm [J. H. Holland, Adaptation in Natural and Artificial Systems (Univ. of Michigan, Ann Arbor, 1975)] is used in conjunction with the multiple scattering theory [L. Sánchis et al., Phys. Rev. B 67, 035422 (2003)] to fabricate a new generation of acoustic devices based on a discrete number of cylindrical scatterers. In particular, acoustic lenses [F. Cervera et al., Phys. Rev. Lett. 88, 023902 (2002)] with flat surfaces have been designed to focus the sound in a fixed focal point for one or multiple frequencies. Each scatterer is carefully placed using the optimization method within the preset boundary conditions, to maximize the pressure contribution in the chosen focal spot. With this method acoustic lenses with very low f-numbers of the order 0.3 and with amplifications over 12 dB have been estimated using a reduced number of scatterers (∼60). Preliminary results obtained from the experimental realization of the designed devices confirm our predictions.
Acoustic waves in discrete media, similarities at meso and nano scales
Authors: Tavossi Hasson
Published: September 2013

In this paper the similarities between the acoustic behavior of a discrete medium of random arrangement of solid spheres, at mesoscopic scales, and thermal vibrations of lattice ions in crystalline solid, at nano scales, are investigated. Results for the ultrasonic waves in random media show that such effects as cutoff frequency, wave dispersion, energy distribution in vibration modes, wave attenuation by scattering and absorption, observed in discrete media, have close resemblance to the similar phenomena observed at atomic scales, such as phonons or lattice thermal vibration of atoms in the crystalline solids. For example, the cutoff frequency in lattice vibration is related to the interatomic spacing, similarly, the cutoff frequency at mesoscopic scales depends on grain separation or grain size. These similarities are also observed in wave scattering and attenuation and their dependence on wave number, kR (k=2π/λ and R is particle size). In this paper experimental measurements with data analysis on cutoff frequency, wave attenuation, and wave dispersion related to the above mentioned similarities will be presented, and the extension of these findings to the behavior of acoustic waves in other discrete media will be discussed.
Evaluation of electromagnetic field interference on sound-pressure level measurements
Authors: Caligiuri Luigi Maxmilian , Sabato Adolfo
Published: September 2013

The recently published IEC 61672-1 defines new standards for sound-level meters and calibrators, giving performance specifications, environmental and electromagnetic criteria, in order to overcome some important faults of the previous IEC 651-1979 and IEC 804-1985. Both of these standards have been in fact amended to include, in particular, specifications for immunity of electrostatic and electromagnetic fields. The interference of such nonacoustics factors can represent, if nonadequately recognized and quantified, an important uncertainty source in sound-pressure level measurements, able to cause errors on measurement result, variable between fractions of dB and some dB. In the present paper we will show the application of a measurement methodology able to quantify, within the framework of IEC 61672-1, the influence of electromagnetic fields on environmental noise measurements, carried out by a class I (according to IEC 651 and 804) integrating sound-level meter. In this way, we have analyzed the effect of different typologies of interfering field sources (characterized by different spectrum and emission features) on some very frequent noise-measurement configuration.
Speed, accuracy, and stability of laryngeal movement in singing
Authors: Titze Ingo R.
Published: September 2013

Motor performance is often quantified in terms of speed, strength, accuracy, and stability of a target gesture, or maintaining a given posture. In the vocal system, this involves primarily the intrinsic laryngeal muscles and the respiratory muscles. Agonist–antagonist pairs of muscles are used to position the vocal folds for phonation (vocal onset), for pitch change, and for registration (as in yodeling). Maximum speed and accuracy are discussed for vocal embellishments such as trills, trillo, scales, arpeggios, yodel, and glissando. This speed and accuracy are interpreted in terms of muscle twitch and tetanic responses obtained in vitro on animal muscles, from electromyographic recordings on humans, and from muscles not easily tested on humans. The laryngeal reflex system is also described, particularly with regard to its ability to stabilize (or destabilize) neurologic tremor originating from the central nervous system.
The sound of Berlin. The noise annoyance you love to hate
Authors: Schulte-Fortkamp Brigitte , Hehner Cay
Published: September 2013

Noise is part of life in Berlin. The Berlin Sound is often described as Berlin is a loud city, but this sound is also a matter of identification. Just like human beings, metropolitan areas may be identified by their gait. People enjoy living in Berlin but they also claim negative health effects and often permanent annoyance caused by daily environmental noise. For instance 1119714 cars demonstrate the volume of traffic from 6.30–9.00 a.m, and another impressive descriptor of the volume of traffic is the number of 1567600 cars from 4.00–6.30 p.m. In a representative survey of 2000 adults, almost all German (80%) citizens are affected by some level of noise pollution. The predominant source of noise in residential areas is road traffic, which remains a nuisance for over half the population, and a source of serious annoyance for some 18%. Next to road traffic, air traffic is the most important transport-related source of annoyance, followed by rail traffic noise. Results from a qualitative survey in a residential area of Berlin give insights into the different perspectives of the noise perception of the investigated subjects and of important parameters with respect to daily life.
Managing environmental noise in Hong Kong
Authors: Li Kai Ming
Published: September 2013

Hong Kong is well known for its economic vibrancy and its hyper densely population: more than 7 million people living in a total area of slightly over 1000 square kilometers of hilly areas. Most of these people live and work in about 20% of the total land area, resulting in probably the highest densities in the world. The high population density is also matched by a large number of vehicles running in the roads. At present, there are over 400000 vehicles operating on a highway network less than 1000 km in length. With all these factors plus many urban activities associated with the rapid growth and development, noise is an important environmental issue in the city. Although there are many dimensions for the quality of life, the acoustic environment is undoubtedly an essential part of it, especially when the people’s aspirations increase as the society develops. This paper summarizes the development of strategies for controlling environmental noise in Hong Kong in the past two decades. The current situation will be addressed and a proposal for an improved traffic noise policy will be presented. [Work supported by the Research Grants Council, and The Hong Kong Polytechnic University.]
Measurements and simulations of an asymmetric finite amplitude ultrasonic field
Authors: Wallace Kirk D. , Holland Mark R. , Miller James G.
Published: September 2013

Transducer arrays used routinely for medical imaging generate diffracting finite amplitude ultrasonic fields that are typically asymmetric and intricate. The goal of this work is to validate a Burgers equation enhanced, nonlinear angular spectrum simulation approach with experimental measurements of an asymmetric finite amplitude ultrasonic field. A one-dimensional transducer array with a 3:2 aspect ratio, separate azimuth and elevation foci, and a nonuniform aperture apodization was immersed in a watertank and was driven by a broadband pulse. A 0.6-mm-diam hydrophone receiver was mechanically scanned to obtain detailed maps of the harmonic content and spatial distribution of the finite amplitude ultrasonic field in nine transverse (00 to 160 mm, evenly spaced) and two orthogonal meridian plane cross sections. The fundamenal (2.3 MHz) component of the field, measured at face of the source, served as input for the numerical simulation (written in MATLAB and run on a notebook computer). Comparisons were performed at the fundamental, second, third, fourth, and fifth harmonics. Overall, excellent agreement was observed between experimental measurements of the nonlinear ultrasonic field generated with an asymmetric array transducer and the Burgers equation enhanced, nonlinear angular spectrum simulations. [Work supported by NIH R01 HL72761.]