bluuebunny/crossref_metadata_2025 huggingface dataset:
A high-frequency broadband energy-intensity boundary element method for specular reflection in three-dimensional reverberant enclosures
Authors: Rouse Jerry W. , Franzoni Linda P. , Bliss Donald B.
Published: October 2013

A new method is presented for predicting the spatial variation of mean-square pressure within three-dimensional enclosures having steady-state, high-frequency broadband sound fields. The enclosure boundaries are replaced by a continuous distribution of uncorrelated broadband directional sources, which provide constituent fields expressed in terms of mean-square pressure and time-averaged intensity variables. Boundary conditions for radiating and absorbing surfaces are recast in energy and intensity variables. Superposition of these source fields in a numerical boundary element formulation leads to the prediction of overall mean-square pressure and time-averaged intensity as a function of position. Both specular and diffuse reflection boundaries can be accommodated. In contrast to the traditional boundary element approach, this method is independent of frequency, and each element has multiple unknowns, namely the strengths of directivity harmonics. For verification, exact analytical solutions for the mean-square pressure distribution in several model problem enclosures were obtained by modal sums and frequency integration and compared to the new method. The comparisons show the method is very accurate, and it is extremely computationally efficient in comparison to classical modal and boundary element approaches. Results also show that diffuse field methods do not provide an accurate simulation for specular reflection cases.
Analysis method for temporal decay of diffuse broadband sound fields in enclosures
Authors: Bliss Donald , Manning Ben , Franzoni Linda
Published: October 2013

An analysis method to predict the behavior of time-dependent broadband diffuse sound fields in enclosures is described. A formulation utilizing time-dependent broadband energy-intensity boundary sources, including propagation time delays, is developed as a numerical boundary element method. An interpolation method is used to re-express the actual delays in terms of a discrete set of integer-multiple delays, thereby facilitating the numerical solution. The method is demonstrated for the prediction of temporal decay in interconnected one-dimensional channels and in two-dimensional enclosures. Temporal behavior is expressed in terms of a higher-dimensional eigenvalue/eigenmode problem, with boundary source strength distributions expressed as eigenmodes. In temporal decay from steady state, solutions exhibit rapid short-time spatial redistribution of energy, followed by long-time decay of a predominant spatial eigenmode. Long-time decay depends on behavior of the most slowly decaying eigenmode and the relative source-panel strengths do not depend on initial conditions. Short-time adjustment and decay depends on initial source characteristics and the relative distribution of absorbing material. An interesting feature of the short-time behavior is that the time-decaying eigenmodes are primarily a manifestation of energy redistribution rather than absorption.
Are acoustically induced flows relevant in fish hearing?
Authors: Kotas Charlotte W. , Rogers Peter H. , Yoda Minami
Published: October 2013

The fluid-filled fish ear contains an irregularly shaped, dense, bony otolith that influences the acoustically induced motion of the adjacent hair cells and thus what fish ‘‘hear.’’ Because incident sound causes the otolith to oscillate with respect to its surroundings, acoustically induced fluid flows are generated near the otolith. A series of experiments was performed using oscillating spheroids as model otoliths to study the induced steady streaming and periodic flows. The studies focused on how the flows change with spheroid (or otolith) geometry and orientation, as well as oscillation (or sound) frequency ω and amplitude s. Experiments were conducted for Reynolds numbers Re ≡ωL2/ν<102 and amplitude ratios ε≡s/L=0.05−0.2, where L is the product of the spheroid aspect ratio and equivalent radius. Results will be presented for oblate and prolate spheroids oscillating at angles up to 45° relative to the spheroid’s axis of symmetry and for flows induced by spheroids driven simultaneously at different frequencies. Understanding these flows may give insight into how fish localize sound sources and lead to new acoustic sensor designs. [Work supported by ONR.]
Probability distributions for locations of calling animals, receivers, sound speeds, winds, and data from travel time differences
Authors: Spiesberger John
Published: October 2013

A new, nonlinear sequential Monte Carlo technique is used to estimate posterior probability distributions for the location of a calling animal, the locations of acoustic receivers, sound speeds, winds, and the differences in sonic travel time between pairs of receivers from measurements of those differences, while adopting realistic prior distributions of the variables. Other algorithms in the literature appear to be too inefficient to yield distributions for this large number of variables (up to 41) without recourse to a linear approximation. The new technique overcomes the computational inefficiency of other algorithms because it does not sequentially propagate the joint probability distribution of the variables between adjacent data. Instead, the lower and upper bounds of the distributions are propagated. The technique is applied to commonly encountered problems that were previously intractable, such as estimating how accurately sound speed and poorly known initial locations of receivers can be estimated from the differences in sonic travel time from calling animals, while explicitly modeling distributions of all the variables in the problem. In both cases, the new technique yields one or two orders of magnitude improvement compared with initial uncertainties. The technique is suitable for accurately estimating receiver locations from animal calls.
Automatic call recognition of cricket songs using image processing
Authors: Brandes T. Scott , Naskrecki Piotr , Figueroa Harold K.
Published: October 2013

An automatic call recognition (ACR) process is described that uses image processing techniques on spectrogram images to detect constant-frequency cricket calls recorded amidst a background of evening sounds found in a lowland Costa Rican rainforest. This process involves using image blur filters along with binary filters to isolate calling events. The binary filters are used to isolate potential calls from background noise, and the blur filters are used to unite discrete call fragments as a single continuous call. Features of these events, notably the events central frequency, duration, and bandwidth, along with the type of blur filter applied, are used with a Bayesian classifier to make identifications of the different calls. Of the 22 distinct sonotypes (calls presumed to be species specific) recorded in the study site, 17 of them are recorded in high enough numbers to both train and test the classifier. The classifier approaches 100% true-positive accuracy for these 17 sonotypes. The high true-positive accuracy of this process enables its use for monitoring singing crickets in tropical forests.
Treatment of ischemic stroke with nanobubbles and ultrasound
Authors: Unger Evan C.
Published: October 2013

The use of perfluorocarbon-filled microbubbles for ultrasound contrast imaging is well known. Now, the next generation of perfluorocarbon-filled bubbles has reached nanoscale and will be evaluated in clinical trials for the dissolution of blood clots in ischemic stroke and other vascular occlusions. MRX-815 nanobubbles are submicron, lipid coated, perfluorocarbon nanobubbles. Due to their small size they are able to penetrate a thrombus. Since they share a lineage with ultrasound contrast agents, their progress can be monitored on diagnostic ultrasound and once they have reached the site of thrombosis ultrasound can be applied externally to activate the bubbles. This activation consists of the bubbles oscillating in the field of ultrasound and cavitating. This mechanical energy works to dissolve the clot and restore blood flow to the ischemic tissues beyond. This process, SonoLysis■ therapy, can be used in tandem with lytic agents or can be used alone in cases where lytic agents are contraindicated. A multicenter, Phase II clinical trial is currently evaluating SonoLysisregistered in the treatment of acute ischemic stroke. Preliminary findings have been encouraging and additional studies are planned.
Molecular imaging and therapy with perfluorocarbon-based site targeted contrast nanoparticles
Authors: Wallace Kirk D. , Hughes Michael S. , Marsh Jon N. , Crowder Kathryn C. , Zhang Huiying , Wickline Samuel A. , Lanza Gregory M.
Published: October 2013

Advances in molecular biology and cellular biochemistry are providing new opportunities for diagnostic medical imaging to ‘‘see’’ beyond the anatomical manifestations of disease to the earliest biochemical signatures of disease. The emerging field of ‘‘molecular imaging’’ encompasses the noninvasive in vivo diagnosis of complex pathological processes by detection of unique molecular signatures. Localization of specific biochemical epitopes with targeted contrast agents affords the unique opportunity for both targeted delivery and deposition of therapeutics. Liquid perfluorooctylbromide nanoparticles (approximately 250 nm mean diameter) elicit little acoustic reflectivity in suspension and strong acoustic contrast when bound and concentrated on a surface (e.g., fibrin deposits in a thrombus). This nanoparticle platform may be functionalized with homing ligands, like anti-αvβ3 integrins, and therapeutic agents. Acoustic imaging of densely distributed biomarkers (e.g., fibrin epitopes) is readily accommodated with fundamental imaging, but for sparse biomarkers (e.g., integrins) we have developed and implemented complementary, nonlinear imaging techniques based upon information-theoretic receivers. Moreover, perfluorocarbon nanoparticles also offer targeted drug delivery, based on contact facilitated lipid exchange, which can be further augmented by ultrasonic insonification.
Ignoring irrelevant dimension variability in frequency discrimination
Authors: Espinoza-Varas Blas , Jang Hyunsook , Jajoria Praveen
Published: October 2013

The ability to ignore variability in irrelevant dimensions while attending to pitch plays a significant role in music perception. In frequency-discrimination tasks, this study examined how this ability depends on four factors: the presentation order and time proximity of target and irrelevant dimensions, the dimension conveying irrelevant variability, and training. Each observation interval displayed pairs consisting of a target (T) followed by a nontarget sinusoid (N) or the reverse (N leading T), with 20–250-ms interstimulus intervals (ISI). Frequency discrimination thresholds (FDTs) were measured in the presence or absence of irrelevant variability in the frequency, duration, or level of either T or N. The ability to ignore irrelevant variability depended on all four factors studied. Irrelevant variability in frequency or level of trailing N tones induced large and persistent elevations in the initial FDTs, especially at short ISIs. Irrelevant variability in T or N duration, T level, or leading N-tone frequency yielded only small and transient FDT elevations. With T-N pairs, irrelevant variability was harder to ignore when it was displayed after, rather than simultaneously with, the target increment. Prolonged training in irrelevant-variability conditions nullified all FDT elevations. The results are interpreted in terms of memory, attention, and discrimination-strategy constraints.
Auditory, but perhaps not visual, processing of Lombard speech
Authors: Vatikiotis-Bateson Eric , Chung Victor , Lutz Kevin , Mirante Nicole , Otten Jolien , Tan Johanna
Published: October 2013

Perception results for three studies are presented that address the role of Lombard speech in auditory, visual, and auditory-visual speech perception. Predictably, when presented in auditory-only conditions with masking noise, listeners recover speech recorded in noise (Lombard speech) better than speech recorded in quiet and presented with the same level of masking noise. However, there is almost no difference in listener performance when Lombard and quiet speech are presented audiovisually with masking noise. Both conditions are enhanced compared to auditory-alone conditions, but there is no indication that the facial motion correlates, demonstrated previously for quiet speech [H.C. Yehia, et al., Speech Commun. 26, 23–44 (1998)], play as strong a role in enhancing auditory-visual processing of Lombard speech, even though Lombard speech is accompanied by larger facial motions. Perhaps it is no surprise that, at a cocktail party, one leans in with an ear rather than with the eyes. [Research supported by CFI and NSERC.]
Changes in ocean infrasonic energy density and vector intensity with changes in wind and ocean surface wave conditions as measured by a freely drifting vector sensor
Authors: D’Spain Gerald L. , Jenkins Scott A.
Published: October 2013

During an experiment in 1.3-km-deep water in the Southern California Bight, the wind speed decreased from about 7 to 1 m/s over a 10-h period, and then increased to 9 m/s over the next 8-h period. Measurements made by a neutrally buoyant, freely drifting vector sensor at 920-m depth show that the corresponding changes in the potential and kinetic energy density levels of the infrasonic sound field have a frequency-dependent delay. The levels in a 0.1-Hz-wide bin at 3 Hz respond to wind-speed changes with approximately a 2-h delay, and the delay in response increases with decreasing frequency at a rate of about 1 h per hertz down to 1 Hz. The corresponding evolution in directionality of the active and reactive acoustic intensity vectors in these same frequency bins and their relationship to the surrounding bathymetry will be presented. The directional spectra of the ocean surface wave field during the experiment were reconstructed using back-refraction modeling with wave data from shore stations and offshore platforms archived by the Coastal Data Information Program to obtain estimates of the temporal variability of the nonlinear wave-wave interactions generating the ocean infrasound. [Work supported by ONR.]
Development of a triaxial pressure-velocity probe for deep submergence applications
Authors: McConnell J. A. , Lopath P. D. , Jensen S. C. , Trivett D. H. , Biesel V. B. , Caspall J. J. , McEachern J. F. , Coughlan R.
Published: October 2013

A triaxial pressure-velocity probe has been developed for the purpose of measuring the ambient acoustic noise field in the ocean at frequencies below 500 Hz. The probe consists of an omnidirectional hydrophone, a compliantly suspended sphere containing a triaxial geophone, and an electronics housing that contains a four-channel preamplifier and a digital compass. All of these components are packaged in a frame which in turn is attached to a deployment cable (i.e., a strength member) and submerged to a prescribed depth. The performance specifications for the transducers include a submergence depth rating of 6 km and a noise floor of 40 dB re: 1 mPa2 per hertz. These two parameters essentially drive the design of the probe and the paper will address these topics from the standpoint of the design evolution that took place in order to meet the specifications. Other aspects of the probe’s development include efforts to mitigate flow-induced noise and shielding the compass from the magnetic field emitted by the geophones. Test data obtained on a prototype unit will be presented. [Work supported by C. M. Traweek at the Office of Naval Research Code 321MS.]
Low-frequency scattering from a mud volcano located offshore Sicily
Authors: Gerig Anthony L. , Holland Charles W.
Published: October 2013

Mud volcanoes are objects that form on the seafloor due to the emission of gas and fluidized sediment from the earths interior. They vary widely in size, can be exposed, proud, or buried, and are of interest to the underwater acoustics community as potential sources of active sonar clutter. Coincident seismic reflection data and low-frequency bistatic scattering data were gathered from one such volcano buried in the Straits of Sicily. The bistatic data were generated using a pulsed piston source and a 64-element horizontal array, both towed over the top of the volcano. The purpose of this work was to appropriately model low-frequency scattering from the volcano using the bistatic returns, seismic bathymetry, and knowledge of the general geoacoustic properties of the area’s seabed to guide understanding and model development. Ray theory, with some approximations, was used to model acoustic propagation through overlying layers. Due to the volcano’s size, scattering was modeled using geometric acoustics and a simple representation of volcano shape. Modeled bistatic data compared relatively well with experimental data, although some features remain unexplained. Results of an inversion for the volcanos reflection coefficient indicate that it is acoustically softer than expected. [Work supported by ONR, NURC.]
Pitch perception in normal and impaired hearing
Authors: Oxenham Andrew J.
Published: October 2013

Despite a century-long debate, there is little consensus on how pitch is coded. This talk will focus on recent psychoacoustic studies that have attempted to shed light on some of the basic principles of pitch coding. The pitch associated with melodies and music is conveyed mainly by lower-numbered harmonics, which are thought to be individually resolved in the peripheral auditory system. When the lower harmonics are removed, the pitch percept becomes weaker and dependent on the phase relations between harmonics, as expected with unresolved harmonics that interact within the passbands of peripheral auditory filters. A number of studies in normal and impaired hearing have shown a connection between harmonic resolvability and pitch strength or salience. However, there are reasons to doubt the causality of this relationship. The evidence for whether resolved harmonics are necessary or sufficient for salient pitch will be reviewed. Finally, some experiments related to the use of pitch cues in segregating speech from competing interferers will be discussed, with particular reference to whether the cues that produce strong pitch salience in psychoacoustic tasks are also those that are most useful in promoting segregation. [Work supported by NIH Grant R01DC05216.]
Investigation of three-dimensional propagation effects at the New Jersey shelf break front
Authors: Moore Kristy A. , Miller James H. , Potty Gopu R. , Lynch James F. , Newhall Arthur
Published: October 2013

Signals recorded on the WHOI VLA/HLA from a ship-towed J15 source during the Shallow Water Experiment (SW06) in the New Jersey Shelf were analyzed for three-dimensional (3D) propagation effects. The signal was a simple CW tone at 93 Hz and the source depth was approximately 50 meters. This 3D propagation effect is a horizontal analogue to the classical Lloyds mirror effect, where fronts can totally internally reflect sound incident upon them at low grazing angles. The direct and reflected modal rays can constructively interfere, having the potential to increase the intensity level by 6dB [Lynch et al., IEEE J. Ocean. Eng., 31 33–48 (2006)]. Trapping of sound between the shelf break front and an internal wave packet may reduce transmission loss by 10 to 20 dB. Bathymetric refraction is also a possible contributor to the reduced transmission loss. Modeling of the Lloyds mirror effect was carried out using the Kraken normal mode model with the environmental parameters of the New Jersey Shelf and J15 source. Analysis of the acoustic recordings of the J15 source and ship noise from the R/V Knorr is consistent with the modeling results. [Work supported by Office of Naval Research.]
On the acoustics of Hellenistic amphitheaters
Authors: Declercq Nico F. , Dekeyser Cindy S. A.
Published: October 2013

Hellenistic theaters are well known for their marvelous acoustics. A numerical study reveals that the seat rows of the theater unexpectedly play an essential role in the acoustics, at least when the theater is not fully filled with spectators. The seats, which constitute a corrugated surface, serve as an acoustic filter that passes sound coming from the stage at the expense of surrounding acoustic noise. Whether a coincidence or not, the famous theater of Epidaurus was built with optimized shape and dimensions.
Phased-array advancement for aeroacoustic measurements—A deconvolution approach for the mapping of acoustic sources (DAMAS)
Authors: Brooks Thomas F. , Humphreys William M.
Published: October 2013

Since the 1990s, there has been a significant increase in the use of phased arrays of microphones in studies of noise sources for both wind tunnel models and full-scale aircraft. This is in spite of the fact that array data interpretation has been burdened with considerable uncertainty when using traditional array processing. Results represent noise sources that are convolved with array beamform response functions, which themselves depend on array geometry, size, and frequency. Recently, Langley Research Center developed breakthrough methodology that decouples the array design and processing influence from the noise being measured, using a relatively simple and robust algorithm. The deconvolution approach for the mapping of acoustic sources (DAMAS) method removes beamforming characteristics from output presentations. This presentation shows results from several airframe noise studies and a MIT air brake noise study conducted at Langley’s Quiet Flow Facility (QFF). It is shown that DAMAS can permit an unambiguous and accurate determination of acoustic source positions and strengths that cannot be otherwise attained. The acoustic community is accepting the methodology and applying it to other applications. At Langley, recent enhancements have been made to the original DAMAS code that allow the determination and separation of coherent and incoherent noise source distributions.
Using method of adjustment to measure informational masking using multitone maskers
Authors: Yost William , Cabael Kristine , Sheft Stanley
Published: October 2013

Previous research has shown that the method of adjustment (MoA) procedure can produce masking results that differ from those obtained with force-choice (FC) procedures in that the MoA procedure produces less informational masking in some contexts and less backward interference masking than FC procedures. A comparison between MoA and FC procedures has not been tested using a random, multimasker condition often used to study informational masking. The present study compared a MoA and a same–different FC procedure using a random 1, 10, or 100 sinusoidal-component masker or a noise masker for a 2000-Hz signal (nominal masker bandwidth was 800 to 6000 Hz). Two groups of 20 naive subjects each were tested. In general, the results indicate that the mean data for the MoA and FC procedures did not differ, but the intersubject variability did, with the MoA procedure yielding smaller variability. The results will be discussed in terms of attention and its relationship to informational masking. [Work supported by grants from NIDCD.]
Indiana University in the history of psychological and physiological acoustics
Authors: Yost William A. , Trahiotis Constantine , Watson Charles S. , Robinson Donald E.
Published: October 2013

The faculty, postdoctoral fellows, and doctoral graduates of Indiana University (IU) in Bloomington, Indiana have played a significant role in the history of the field of psychological and physiological acoustics, especially since 1960. The department of Psychology (now Psychological and Brain Sciences) and that of Speech and Hearing Sciences, along with the former Center for Neural Science, provided a rich environment for many of us to develop as psychological or physiological acousticians. These researchers, their students, and their students students have had a far reaching impact on psychological and physiological acoustics. This poster will describe some of the key IU people, their various contributions, and the academic connections among these IU researchers and many others in the field. The poster will also discuss IUs success as a major contributor to our field.
Sound source identification by compressive sensing
Authors: Arora Raman , Lutfi A. Robert
Published: October 2013

Compressive sensing (CS) is an emergent technology that has found increasing application in the areas of broadband signal monitoring and image reconstruction [D. Donoho, IEEE Trans. Info. Theory 52, 1289–1306 (2006)]. It involves a novel approach to sampling in which the salient information in signals is recovered from the projection of observations onto a small set of randomly-selected basis functions. The major attraction of CS is its capacity for accurate reconstruction based on sparse sampling and little or no prior knowledge of signals. This feature makes it attractive, as well, for application to the problem of sound source identification; an allied task in which sound waveforms as signals are to be classified according to their generating source. In the present paper CS is applied to examples of sound source identification tasks taken from the human psychoacoustics literature. The examples are used to demonstrate in these cases potential advantages of CS classification over traditional decision algorithms that sample at the Nyquist rate. Parallels to the human data are also noted, entertaining speculation as to the role CS classification might play in theoretical thinking about human sound source identification. [Research supported by NIDCD grant 5R01DC006875-02.]
Nonlinear oscillations of an object buried in soil
Authors: Zabolotskaya Evgenia A. , Ilinskii Yurii A. , Hamilton Mark F.
Published: October 2013

A model is presented for nonlinear oscillations of an object buried in soil. The derivation is based on Lagrangian mechanics. The stress-free boundary condition on the surface of the ground is satisfied by introducing an image source pulsating in antiphase with the buried object. An equation of Rayleigh-Plesset form is obtained that describes the nonlinear volume oscillations in the elastic medium. In the linear approximation, the model yields an analytic expression for the resonance frequency. When elasticity of the soil is ignored, or when its elastic properties are presumed independent of depth, the resonance frequency decreases as burial depth is increased, tending toward a limiting value at saturation. When the shear modulus of the soil is permitted to increase with depth, the resonance frequency no longer saturates but instead increases with depth after passing through a minimum value. Perturbation theory is used to estimate weakly nonlinear effects. Attention is focused on second-harmonic and difference-frequency generation. [Work supported by ONR.]
Propagation in an elastic wedge using the virtual source technique
Authors: Abawi Ahmad T. , Porter Michael B.
Published: October 2013

In this paper the virtual source technique is used to model propagation of waves in a range-dependent ocean overlying an elastic bottom with arbitrarily-shaped ocean-bottom interface. The virtual source technique provides the means to impose boundary conditions on arbitrarily-shaped boundaries by replacing them by a collection of sources whose amplitudes are determined from the boundary conditions. The method is applied to propagation in an elastic Pekeris waveguide, an acoustic wedge and an elastic wedge. In the case of propagation in an elastic Pekeris waveguide, the results agree very well with those obtained from the wavenumber integral technique, as they do with the solution of the parabolic equation (PE) technique in the case of propagation in an acoustic wedge. The results for propagation in an elastic wedge qualitatively agree with those obtained from an elastic PE solution.
Bayesian geoacoustic inversion in a range-dependent environment
Authors: Chapman Ross , Jiang Yongmin , Hodgkiss Bill
Published: October 2013

In August 2006 a series of experiments was carried out on the New Jersey continental shelf to investigate geoacoustic inversion in a range-dependent shallow water environment. The experimental site was instrumented with multiple oceanographic sensing systems to provide spatial and temporal ground truth of the ocean environment throughout the experiments. The acoustic experiments used multiple receiving systems and sound sources operating over a large frequency band from 50 to 20 kHz. This paper presents results from inversion of low-frequency (<1000 Hz) data obtained along a radial track from one of the 16-element vertical line arrays. The track was surveyed with a chirp sonar to establish bathymetric and subbottom ground truth. Continuous wave tones were recorded at ranges of 1, 3, and 5 km where the source ship held station for several minutes. Bayesian matched field inversion was applied at each of the sites. The effects of unknown range dependence were taken into account by estimating the data error covariance from multiple data windows at each range station. The inversions indicate that the long-range experimental geometry provided reliable estimates for the sea floor sediment parameters in the range-dependent environment. [Work supported by ONR Ocean Acoustics Team.]
Complex-valued coded excitations for acoustical channel measurements
Authors: Xiang Ning , Li Shu
Published: October 2013

Coded signals have been increasingly applied in acoustical/bio-ultrasonic measurements in order to increase the measurement quality or to cope with demanding requirements [Xiang and Schroeder (2003)]. Increasing interest in coded signals as acoustical excitations has prompted development of efficient correlation algorithms [Daigle and Xiang, J. Acoust. Soc. Am. (2006)]. These algorithms allow efficient processing of complex-valued sequences as needed in critical acoustical measurements, such as using simultaneous sources. Exploiting excellent correlation properties of some coded signals, this work applies complex-valued quadratic residue (QR) sequences and Zech-logarithm sequences in both base-band acoustical channel measurements using sequential excitations and band-limited acoustical channel measurements using amplitude-modulation schemes. Numerical simulations and laboratory experiments carried out in this work demonstrate feasibility of the techniques. This paper discusses advantages and challenges when using coded excitations in potential acoustical applications.
On the perception of crackle in noise radiated from military jet aircraft
Authors: Gee Kent L. , Sparrow Victor W. , Atchley Anthony A. , Gabrielson Thomas B.
Published: October 2013

Crackle, a phenomenon sometimes associated with supersonic jet noise, has been usually quantified using the time waveform skewness. Skewness is a measure of the asymmetry of the waveform probability density function (PDF). This paper discusses whether skewness is a sufficient descriptor for the perception of crackle in jet noise waveforms. As part of this study, methods by which non-Gaussian waveforms may be generated have been investigated. By passing a Gaussian noise signal through an appropriately selected nonlinear transformation function, a simulated waveform can be created that has the same mean, variance, skewness, kurtosis, and power spectrum as a crackle-containing F/A-18E waveform recorded 18 m from the aircraft during a tie-down test. In addition, the PDFs of the simulated signal and the recorded signal are nearly identical. Despite the essential equivalence of the two waveforms from a statistical and spectral perspective, there is no perceived crackle when the simulated waveform is played back. Further analysis of the two waveforms suggests that perception of crackle is likely related to rapid changes in acoustic pressure that reveal themselves in the characteristics of the time derivative of the waveform than of the waveform itself. [Work supported in part by SERDP and ONR.]
The acoustics progeny of R. Bruce Lindsay
Authors: Rogers Peter H.
Published: October 2013

R. Bruce Lindsay served on the faculties of Yale University from 1923 to 1930, and Brown University from 1931 until his death in 1985, a total of sixty-two years. Over that time he produced at least thirty-five Ph.D. students and a like number of masters students. Many of these students were active in acoustics, held faculty positions, and went on to produce Ph.D. students of their own. This paper attempts to trace the major branches of the acoustics family tree of R. Bruce Lindsay, which is now in at least its fifth generation. The members of the Lindsay family tree have made, and continue to make, significant contributions to acoustics. For example, it is interesting to note that James Finneran, the 2002 winner of the ASAs R. Bruce Lindsay Award, is R. Bruce Lindsays academic great-great grandchild.
Three-dimensional normal mode vibration plus acoustic analysis of two exemplary old Italian violins
Authors: Bissinger George , Rowe Danial
Published: October 2013

A Polytec three-dimensional scanning laser system capable of measuring in-plane and out-of-plane violin corpus vibrations was used to measure mobilities in the top, ribs, and back of two exemplary old Italian violins, the 1715 Titian Stradivarius and the 1735 Plowden Guarnerius del Gesu, plus partial scans of the Willemotte Stradivarius (1734) and a Joseph Curtin (2006), back plate and top plate, respectively. The ratio of in-plane to out-of-plane mobility was extracted for the first time for these violins over the frequency range of 0–5 kHz. Comparing only the averaged top plate mobilities of the 1715 Stradivarius and the 1735 Guarneri del Gesu with the 2006 Joseph Curtin revealed no important old-new trend. Among the low-lying (below 600 Hz) signature corpus modes, fit results for total damping revealed higher old Italian total damping only for the upper first corpus bending mode. Analysis of higher frequency damping behavior is currently under way. These measurements were accompanied by acoustic measurements over a sphere in an anechoic chamber of all these violins (plus a 2006 Sam Zygmuntowics violin) to compute radiation efficiencies for each violin.
Attracting insects with an acoustic laser
Authors: Lau Kent , Garrett Steven
Published: October 2013

It has been demonstrated that female Mediterranean fruit flies (Ceratitis capitata) are attracted to a trap by a pure tone at approximately the spectral peak (330 Hz) of the males mating call [Mankin et al., J. Econ. Entomol. 97, 1299–1309 (2004)]. Recent research [Sueur et al., ‘‘Sound radiation around a flying fly,’’ J. Acoust. Soc. Am. 118, 530–538 (2005)] suggests that a more complex tone that combines an amplitude-modulated fundamental and a second-harmonic component could produce more effective acoustic bait. We will describe a thermoacoustic sound source [S. L. Garrett and R-L. Chen, Echoes 10, 4–5 (2000)] that combines two closely tuned quarter-wavelength resonators designed to produce a beating fundamental of adjustable modulation depth. A third source produces the second harmonic. The trio of sources generates the desired signal at levels of 90 to 100 dB 1 meter from the array. Since the sound is produced from electrically heated filaments, no oscillators, amplifiers, or electro-acoustic transducers are required. When the pair of fundamental resonators are placed side-by-side, the beating occurs uniformly in space. When placed back-to-back, the dipolar radiation pattern rotates to produce the beating in time at any fixed location. We hope to have results with insect subjects by the time of the meeting. [Work supported by an endowment from United Technologies Corporation.]
Finite-element transient calculation of a bell struck by a clapper
Authors: Lau Bjrn-Andre , Wriggers Peter , Schneider Albrecht , Bader Rolf
Published: October 2013

A finite-element calculation of a bell struck by the bell clapper was performed as a transient contact problem. The geometry of the bell was taken from a real bell which was carved especially in behalf of this research. The eigenmodes and eigenfrequencies of the bell were calculated in advance, being in good agreement with the measured frequencies. The clapper/bell contact time and impulse shape show the expected behavior. The impulse shape is a Gaussian impulse with a tendency of a sharper attack slope and a softer decay slope. The periodical shape of the spectrum of this impulse caused by its finite width with zero values for some frequencies is shown. Nevertheless, this spectrum also drives the frequencies of the bell within the low-amplitude region of the driving impulse with expected and measured strength. The reason for this mode energy transfer is discussed. Furthermore, the sound of the bell is calculated as radiation from its surface and analyzed with signal-processing tools like wavelet transforms or autoregressive models.
Education in medical acoustics
Authors: Porter Tyrone
Published: October 2013

The field of medical acoustics has grown tremendously in the last 30 years. Sophisticated ultrasound scanners are utilized to image a developing fetus in the womb or blood flow in the vessels. High-pressure acoustic pulses travel through muscle, fat, and capillary beds to pulverize kidney stones with minimal damage to the intervening tissue. Gas-based microbubbles stabilized with polymeric or liposomal shells are injected into the vasculature to enhance the contrast in ultrasound images or to deliver life-saving drugs. Due to the interdisciplinary nature of medical acoustics, educating the next generation of clinicians, engineers, and researchers within the field has become more challenging. Students must gain some understanding of a variety of concepts, including the derivation of the wave equation, the effect of biological media on the propagation of ultrasound (attenuation, scatter, etc.), signal-processing techniques for converting scattered sound into images, and the effect of viscoelastic shells on the forced oscillation of microbubbles. Armed with this knowledge, medical acousticians will continue to develop innovative diagnostic and therapeutic applications for ultrasound.
Working group on ‘‘The effects of sound on fish and turtles’’: An update
Authors: Fay Richard R. , Popper Arthur N.
Published: October 2013

In order to develop acoustic exposure criteria for fish and marine turtles based on scientific evidence, an ASA Standards Working Group was formed with a membership that includes basic scientists expert on fish and turtle bioacoustics, physical acousticians with special expertise in marine bioacoustics, and several individuals with expertise on effects of anthropogenic sound in the marine environment. This presentation is a summary of the group’s progress to date. One of the Working Group’s goals is to publish several papers, one on what is known about damage risks due to exposure to underwater noise (e.g., from pile driving, seismic exploration, sonar systems), and one assessing the efficacy of various measures to mitigate adverse effects of noise exposure. The working group has tentatively decided that the fish potentially affected should be categorized with respect to their hearing sensitivity (potential for auditory system damage) and whether the species is known to detect sound pressure or acoustic particle motion. Over the next year to 18 months, the Working Group will be evaluating the known effects of sound sources on fish and turtles, identifying areas in which further research is needed, and beginning to develop noise exposure criteria for both turtles and fish.
A system for understanding violin bowing technique through measurement of physical dynamics
Authors: Young Diana
Published: October 2013

Presented here is a custom-built sensor system for the measurement of violin bowing parameters. An improvement on previous designs, the system includes a set of accelerometers, gyroscopes, and force sensors, installed on a carbon fiber violin bow. In addition, another set of inertial sensors, as well as an electric field position sensor, are mounted on the test violin. When taken together, the data from the violin and bow are combined to achieve estimates (relative to the violin) of the three primary bowing parameters: force, speed, and bow-bridge distance. Because the system is relatively compact and lightweight, it is suitable for operation in realistic performance environments outside the laboratory setting. As such, it is possible to obtain detailed physical gesture data from real performances. The potential of the system is explored in several early studies to investigate the interaction of bowing parameters in common strokes. Distinctions between novices and experts, as well as differences between technique and style among experts, are discussed.
Haro Strait geometry from time-domain data
Authors: Tolstoy A.
Published: October 2013

This paper presents results which relate to the geometry of various Haro Strait scenarios. In particular, from the time-domain data we can estimate the source range, source depth, individual phone ranges, individual phone depths, and water depths at the source and at the array. These parameters are optimally estimated based on the time-domain signals alone. We assume that the bottom is sloping, consider up to four reflections (surface, bottom, surface-bottom, and bottom-surface), and allow for up to 16 phones of data. We see that nonuniqueness can still be an issue even using a great deal of time-domain data. However, these parameters are nearly uniquely estimated if additional constraints are considered, particularly on the arrays. Some of the optimal parameters are ‘‘confirmed’’ by simulating the signals for the predicted geometries by means of a pulse PE (RAMGEO) propagation code (courtesy of M. Collins) and then comparing those simulated signals with the observed data.
Spectral parameter imaging of the corneal stroma
Authors: Silverman Ronald H. , Gal Omer , Patel Monica , Coleman D. Jackson
Published: October 2013

Frederic L. Lizzi was a pioneer in the fields of high-frequency ultrasound and tissue characterization. This report details use of spectral parameter imaging of very-high-frequency radio frequency data for characterization of the cornea. The corneal stroma consists of broad 1–2-micron-thick belts (lamellae) embedded in a proteoglycan matrix. The lamellae consist of collagen fibrils 30 nm in diameter with center-to-center spacing of about 60 nm. Any disturbance to this orderly arrangement will result in loss of optical transparency. Parameter images representing the slope, intercept, and midband fit to the calibrated power spectrum were generated by post-processing of radio frequency data of 35- and 70-MHz scans of the cornea. Stromal backscatter was significantly higher at 70 MHz than at 35 MHz. In an uncomplicated LASIK-treated cornea examined 6 years postsurgery, significant differences in backscatter between the stroma anterior versus posterior to the LASIK interface were observed. This may relate to alteration in lamellar organization, even in the absence of loss of optical transparency. Frequencies beyond 50 MHz offer a probe of tissue microstructure that could be employed in evaluation of stromal organization. [Work supported by NIH Grant EB000238 and Research to Prevent Blindness.]
Subjective response to absorption and aperture size variations in complex computer-modeled coupled volume systems
Authors: Bradley David T. , Wang Lily M.
Published: October 2013

Computer models of an imagined but realistic coupled volume concert hall have been made to obtain room impulse responses for several different configurations of the space. A coupled volume concert hall is typified by a large, absorbent main volume linked to a smaller, reverberant auxiliary space through a series of sonically transparent openings. Absorption and aperture size have been modified in this study to create each configuration of the virtual hall. Auralizations of the configurations have been used in paired-comparison tests to determine listener preference for the various sound fields, including some that exponentially decay and others that show a double-sloped decay. The results from this subjective testing were statistically analyzed using Thurstone Case V and multidimensional scaling methods. These results will be presented and contrasted with objective parameters extracted from the impulse responses generated by the computer modeled-configurations of the hall.
Effects of dialect variation on speech intelligibility in noise
Authors: Clopper Cynthia G. , Bradlow Ann R.
Published: October 2013

Recent research has shown that listeners can classify talkers based on their regional dialect of American English (AE). The present experiment explored the effects of regional dialect variation on speech intelligibility. Participants from various AE dialects transcribed meaningful English sentences mixed with noise. The sentences were produced by male and female talkers from four different AE regional dialects. At a favorable signal-to-noise ratio (−2 dB), intelligibility of General American and Southern talkers was significantly better than Northern and Mid-Atlantic talkers, and was significantly better for the Northern than the Mid-Atlantic talkers. At a more difficult signal-to-noise ratio (−6 dB), intelligibility was equally poor for the Southern, Northern, and Mid-Atlantic talkers, but remained significantly better for the General American talkers. No effects of listener dialect were observed. Thus, speech intelligibility in noise was generally poorer for more phonologically marked dialects (e.g., North, Mid-Atlantic) than less-marked dialects (e.g., General American). However, noise had differential effects on dialect interference; intelligibility of marked dialects was graded at easier signal-to-noise ratios, but marked dialects were equally difficult to transcribe at unfavorable signal-to-noise ratios, suggesting that dialect information may be conveyed by aspects of the signal that are relatively vulnerable to perceptual disruption by noise.
Vertical directionality of noise at two shallow water sites
Authors: Duda Timothy F. , Lynch James F. , Newhall Arthur E. , Abbot Philip A.
Published: October 2013

Noise recorded with 16-element vertical line arrays moored at two sites near 80-m water depth has been analyzed. One site is south of New England (Shelfbreak PRIMER, June 1996), the other south of China in the South China Sea (ASIAEX, May 2001). Both sites exhibited downward refracting conditions, so that a noise notch is realizable, and both exhibit internal gravity waves. The waves were more plentiful and of larger amplitude at the South China Sea site. Sound in a 40-Hz band centered at 135 Hz was extracted and separated into vertical beams using delay and sum beamforming. At each location, noise lower than the median level exhibited a peak near zero degrees for each data set (near-horizontal arrival). Noise higher than the median level in the New England data set exhibited a 5-dB noise notch, with peak levels at about ±15 deg. Noise higher than the median level in the South China Sea data set did not show the notch and was essentially flat between 10 and −10 deg. The results are consistent with observed fluctuating propagation between fixed sources and re- ceivers at the sites, and with differences in coupled-mode propagation through the two internal-wave fields.