bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental influences on low-frequency, shallow-water acoustic propagation and inversion.
Authors: Frisk George V.
Published: October 2013

Historically, the seabed has been considered to play the dominant role in shallow-water acoustic propagation at low frequencies. As a result, propagation models have focused on the incorporation of accurate values of bottom properties, while inversion techniques have concentrated on the determination of geoacoustic properties of the seabed. In recent years, however, the assumption of a benign water column has increasingly come under scrutiny in addressing both the forward and inverse problems. This paper addresses these issues as they relate to a measurement and inversion methodology in which acoustic data are acquired on synthetic radial apertures that are created using a moving source/receiver configuration in concert with precision navigation. These data can be transformed into the horizontal wavenumber domain to obtain an estimate of the propagation characteristics of the waveguide; namely, its modal content. The modal spectra can then be inverted using a variety of techniques to determine estimates of the waveguide parameters, specifically the geoacoustic properties of the seabed. The issues associated with the successful implementation of this modal mapping method in a highly variable shallow-water environment are discussed. [Work supported by ONR.]
Current applications of ultrasonic resonators to biomolecular studies.
Authors: Chalikian Tigran
Published: October 2013

The most versatile family of instruments providing the highest precision of acoustic measurements in the lowest sample volumes utilizes the method of fixed-path interferometer. The speed of sound in a medium is a simple function of its density and compressibility. Both parameters are determined by and, therefore, reflect the entire spectrum of intra- and intermolecular interactions within the system. In addition, compressibility probes the pressure response of these interactions. Current resonator-based instruments provide reliable measurements in diluted solutions of biological compounds with solute concentrations on the order of 1 mg/mL and solution volumes of 1 mL. They require less than 1 mg of sample, a range acceptable for the majority of biochemical and biophysical investigations. Ultrasonic velocimetric measurements have been employed to study a range of biologically relevant reactions, including the folding/unfolding transitions of proteins and helix-to-coil transitions of nucleic acids, as well as drug-DNA, ligand-protein, protein-protein, and protein-DNA association events. The limiting factor in such investigations is the need to rationalize the measured properties (volume, compressibility, and their derivatives) in terms of microscopic events, such as solute-solvent interactions. This presentation reviews biomolecular applications of acoustic measurements and discusses the development of approaches for microscopic interpretation of macroscopic volumetric observables.
Use of resonator method for body fluids composition assessment.
Authors: Klemin Viktor
Published: October 2013

Ultrasonic resonator method of body fluids composition evaluation is described. The experimental data on assessment of whole blood, blood serum, gastric juice, and saliva are presented. The developed method is based on the assumption of additivity of the contributions of major components of fluids in their acoustic characteristics. The acoustic characteristics measured by the ultrasonic resonator method include the speed and absorption of ultrasound and their frequency and temperature dependences. The device for evaluation of body fluid composition comprises differential ultrasonic resonator cells with the volume of 80 mkl each, operating at about 8 MHz, mounted in a micro-thermostat, and a compact electronic unit. The method allows for simultaneous determination of total protein, Na+ and K+, in saliva and gastric juice, lipid components (cholesterol total, cholesterol of high and low density, and triglycerides), the total protein and protein fractions in blood serum within a very short period of time, on the order of minutes, in contrast to conventional time consuming tests. Other advantages of the proposed technology include the reagent-free nature, no need for sample pretreatment, ease-of-use, and low cost. The accuracy of ultrasonic method for body fluid composition assessment is comparable to that of conventional time-consuming and expensive assays.
Rapid identification of candidate materials for tonpilz head-mass design.
Authors: Porter Scott P. , Markley Douglas C. , Van Tol David J. , Meyer Richard J.
Published: October 2013

Optimum performance of a tonpilz transducer head-mass section is often achieved when the mass is minimized and the stiffness is maximized. High stiffness keeps head-mass modes away from the band of interest with minimal material; low mass maximizes the motor section aspect ratio and reduces the stored energy in the head-mass, raising the electromechanical coupling coefficient. Therefore, the material selected for the head-mass construction plays an integral role in transducer performance. In the practical design of tonpilz radiating heads, a tool which can rapidly identify the materials best suited for a given design is desirable. The figure of merit, Eρ3, has traditionally been used. This figure of merit, however, is based on thin-plate approximations. Most actual tonpilz head-masses require thick-plate theory for accurate analysis. In this paper, the authors use a numerical routine to rapidly assess the thick-plate behavior of various materials and rank their suitability for a given head-mass geometry. These results are corroborated with finite element modeling. Finally, the thick-plate ranking scheme is compared to the traditional figure of merit. The results of this comparison challenge established assumptions about the best materials for head-mass design and identify ceramic materials as strong candidates for future designs.
Infrasonic microphone.
Authors: Marston Timothy , Gabrielson Thomas B.
Published: October 2013

The high cost of many infrasonic transducers can be a setback for universities interested in performing research in the field of infrasound. Reasonably effective infrasonic transducers can be constructed in the laboratory, however, and for a fraction of the cost. A simple, inexpensive infrasonic microphone that operates on the principle of carrier demodulation has been constructed. Noise analysis of the microphone demonstrates its potential usefulness for cost-effective field research and deployment in temporary infrasonic arrays. [Research funded by the Penn State Applied Research Laboratory Educational and Foundational Fund.]
Does a brass-instrument’s timbre depend on the alloy from which it is made?
Authors: Pyle Robert W.
Published: October 2013

Most brass players with a few years experience would give an affirmative answer to the question posed in the title. In the past, audible differences have proven elusive when pursued through spectral analysis of sustained tones, perhaps because the right question was not asked. This talk will examine several attributes of trombone spectra. The trombone used has a “modular construction” so that different bells can easily be installed on an otherwise unchanged instrument. A clear difference, consistent with the player’s and listener’s perception of the tone quality, emerges between yellow brass (70% Cu, 30% Zn) and red brass (90% Cu, 10% Zn). Transient behavior, particularly during the attack, is at least as important to the performer as sustained sounds. Here, too, differences are attributed to the alloy. Yellow brass is characterized by “crisp” attacks, red brass by “rounded” attacks. This talk will also analyze attack transients, even though attacks that are perceived as similar appear quite variable when examined in detail.
Imitating the human voice: The renaissance cornett and sackbut.
Authors: Campbell Murray
Published: October 2013

In the 16th century the lip-reed instruments most commonly used in sacred and chamber music were the cornett (Italian “cornetto”) and the sackbut (Italian “trombone”). The sound ideal described by contemporary writers for these instruments was clearly distinguished from the ceremonial and often military splendor of the trumpet ensemble: the cornett and the sackbut were expected to produce dynamic levels and timbres comparable to those of human singers. The acoustical features, which make it much easier to approach this ideal on the renaissance instruments than on modern trumpets and trombones are explored through measurements on original instruments and modern reproductions.
Simulations of converging shocks in water.
Authors: Eliasson Veronica , Henshaw William D. , Dimotakis Paul E.
Published: October 2013

Numerical simulations of weak shocks in water traveling through a convergent geometry were performed. The convergent geometry is surrounded by an elastic solid, which is deformed by the fluid, thereby, generating elastic waves in the solid, which in turn affect the liquid, thus creating a coupled fluid-structure problem. Here, we use the Overture suit, which is a code for solving partial differential equations on curvilinear overlapping grids using adaptive mesh refinement. In particular, we use a multiphysics solver to solve the fluid-structure problem. The Euler equations with a stiffened equation of state are used in the fluid domain and the linear elasticity equations are used in the solid domain. The solutions at the interface between the fluid and the solid are matched using continuity of normal velocities and forces. Preliminary results indicate that the wave speed of the material has a large influence on the behavior of the converging shock. The numerical simulations are also compared to schlieren photographs and pressure measurements obtained from experiments. Results can enhance the design of marine structures with convergent sections subjected to dynamic loading events. [Work supported by ONR.]
Measurement methodologies for the analysis of influence of surface panels and their vibrations on interior cabin noise.
Authors: Wu Sean , Pierce Allan
Published: October 2013

In the design of quiet automobile compartments, one analyzes the influence of individual panels and enclosure surface leaks on noise received in a specific region (the location of the driver’s ear position). Two recent papers [Hald et al., Internoise (2006); Wolff, Internoise (2007)] suggest the needed measurement process can be shortened using a sound source at the typical listener position, taking measurements over the enclosure surface, and then invoking the principle of reciprocity. The present paper clarifies the analytical discussions of these earlier papers with improved and more nearly rigorous derivations and suggests improved measurement methodologies. One exemplary model considered is that of an arbitrarily shaped cavity with sound absorbing walls that are also moving due to external influences. The boundary condition on the pressure field inside the cavity is shown to be well approximated such that the normal component of the pressure gradient is a superposition of a constant times the pressure itself (locally reacting surface with finite impedance) plus a constant times the portion of the surface velocity that is due to the external sources. The pressure inside the cavity can be solved by Green’s function techniques, and the Green’s function can be proven to rigorously satisfy reciprocity.
Developing audio-visual associations in infancy.
Authors: Lacerda Francisco , Klitfors Eeva , Marklund Ellen
Published: October 2013

To investigate how possible biases in matching of object sizes with sound intensities may be influenced by the ecological relevance of the potential associations, three groups of Swedish infants (4, 6, and 8 months of age) are being tested in their preferences to match speech or nonspeech sounds of different intensities with visual stimuli showing faces or unanimated objects of different sizes. The infants’ audio-visual matching preferences are measured by the cumulative time that the infants' gaze vector was directed to each of the faces and objects simultaneously displayed on the screen, in response to the presentation of an acoustic stimulus (either a speech sound or a nonspeech sound). The results appear to suggest a general trend towards matching of visual prominence with sound intensity, when the ecological relevance of the audio-visual associations was high (i.e., matching speech sounds with faces and nonspeech sounds with unanimated objects) but the pattern seems to be disturbed when only nonecologically relevant matches are possible. [Work carried out within grants from The Bank of Sweden Tercentenary Foundation, Grant No. K2003:0867, MILLE, from EU-NEST Project No. 5010, CONTACT, and from the Knut and Alice Wallenberg Foundation, Grant No. KAW 2005.0115.]
Voice familiarity helps infants tackle variability in the speech signal.
Authors: van Heugten Marieke , Johnson Elizabeth
Published: October 2013

The acoustic realization of lexical items produced by different speakers can vary greatly. Current research suggests that infants, unlike adults, struggle to cope with this lack of invariance in the realization of words. Although 7.5-month olds are able to recognize words across different utterances when produced by speakers of the same gender with similar voices, they fail to do so when target words produced in a female voice are subsequently produced in a male voice [Houston and Jusczyk (2000)]. Note that all work in this area has used disembodied unfamiliar voices to test infants. In the current study, we ask whether infants might perform better under more ecologically valid conditions, i.e., when tested on familiar rather than unfamiliar voices. Using the headturn preference procedure, infants were familiarized with passages spoken by their mother. During the test phase, they were presented with their father’s voice producing isolated repetitions of familiarized target words. Preliminary results suggest that infants may recognize words across different utterances produced by speakers of different genders if they are highly familiar with both the male and female speakers. In other words, infants may handle variability in the realization of words better when tested on familiar rather than unfamiliar voices.
Finding physically motivated classification features using finite element models.
Authors: McLaughlin Jack , Owsley Lane M.D.
Published: October 2013

Finite element models (FEMs) for simple shapes such as spheres, cylinders and pipes can be used to uncover potential features for classification by sonar systems. Analyses were conducted of the simulated, bistatic returns over a wide range of aspects using FEMs for a solid steel cylinder and a cement pipe all in free space. Salient characteristics noted in this way were then sought in field data collected from the same or similar objects during the SAX04 experiment and two other data collections conducted in a test pond at the Naval Surface Warfare Center in Panama City, Florida. Characteristics robust enough to appear in both simulated data and field data are candidates to serve as classification features for similarly shaped objects. It is found that FEMs can provide important pointers to classification features that are closely tied to the physics of reflection. As such, the variability of these features in the face of object burial and multipath can be more easily assessed than statistical spectral features. [This work was supported by the U.S. Navy Office of Naval Research.]
Processing techniques applied to underwater target echoes and their relationships.
Authors: Houston Brian H. , Bucaro Joseph A. , Kraus Larry , Simpson Harry J. , Yoder Timothy J.
Published: October 2013

Interest in acoustic scattering from underwater unexploded ordnance (UXO) has been increasing because of the growing need for sonar technology able to detect submerged UXO and to efficiently separate these detections from those due to natural and man-made clutter. Recent efforts range from laboratory and numerical studies seeking to understand the basic structural acoustic echo formation processes and the environmental effects on them to field exercises determining how well a particular detection/identification technology performs. This paper discusses several important scattering-based constructs, which have been utilized in both the basic UXO studies and the technology exercises as well. They include: (1) σ(ω, θ), the frequency/angle-dependent scattering cross section; (2) standard imagery, oftentimes implemented with synthetic aperture arrays; (3) reflection tomography imaging; and (4) supersonic imaging using holographic techniques. Without a clear appreciation for the differences among the constructs, it is difficult to properly relate the results of the various studies. We have measured the broadband scattering from several underwater UXO targets using laboratory, rail-based, and AUV systems and processed the data using the above constructs. The use of a common, high quality UXO scattering data base in this process helps clarify the differences and relationships among the constructs. [Work supported by SERDP and ONR.]
Shallow water horizontal signal coherence measurements with use of mobile acoustic sources to create synthetic aperture arrays.
Authors: Abbot Philip , Dyer Ira , Emerson Chris
Published: October 2013

Horizontal signal coherence length was measured in shallow water using a reciprocal synthetic aperture array created from multiple signals radiated by a mobile acoustic source, and a slowly drifting omnidirectional receiver. The tests were conducted in September, 2008, in shallow water (125 m depth) of the South East China Sea. Source and receiver depths were 61 m. Twelve hyperbolic FM slides per minute were transmitted while the source moved horizontally at 2.5 m/s, maintaining a nearly constant range of ~6 km to the receiver. Received signals were matched-filter processed, phase-corrected to form an equivalent linear array, then coherently combined using a synthetic aperture time delay beamformer. The beamformer output signal gain versus the number of elements in the array, N (using 2 ⩽ N ⩽ 512 transmissions), was compared to the theoretical limit (20 log, N). The coherence length, defined to be L/λ at a point 3 dB down from the limit, was determined. At 900 Hz, the correlation length was L/λ ≈ 40 (N=7, over 40 s). At 600 Hz, it was L/λ ≈ 10 (N=3 over 8 s). The degradation at 600 Hz is due to substantially smaller signal-to-noise levels at the element level. Partial coherence is observed at both frequencies, even at N=512.
Fractal surfaces: Generation and acoustic scattering prediction.
Authors: Olson Derek R. , Bradley David T.
Published: October 2013

Typical acoustical diffuser design results in diffuse sound scattering only for a limited frequency band, which is problematic given the breadth of the human audible frequency range. Surfaces exhibiting fractal geometries may address this problem due to their self-similarity over multiple scales. Stochastic fractals, such as the random midpoint displacement (RMD) fractal, are well-suited to this usage since they can be mapped onto physical surfaces appropriate for acoustical diffusers. In the current project, virtual RMD fractal surfaces were generated and then constructed using a 3-D printer. A pilot study has been conducted to determine the scattering properties of the fractal surfaces using a numerical prediction scheme carried out using the boundary element method (BEM). Experimental measurements of the scattering properties were also carried out according to ISO 17497. The numerical predictions and experimental measurements were contrasted to improve numerical prediction accuracy and optimize the fractal design parameters of acoustical diffusers. These parameters include surface roughness, fractal dimensionality, number of iterations, and the random number probability distribution function. The comparison of the numerical and experimental results will be presented along with effects of the fractal design parameters.
Investigating multifractals to quantify diffuseness in rooms.
Authors: Hart Noel W. , Xiang Ning
Published: October 2013

Diffuseness, an important room acoustics parameter, currently has no accurate objective method of quantification. Most methods that claim to be able to quantify it require specialized equipment or guesswork. Multifractals present a recent method that allows diffuseness in rooms to be quantified by analyzing a single room impulse response [Loutridis, JASA 125(3) (2009)]. This method will be verified by acoustical measurements in rooms of various degrees of diffuseness. Since this method has only been demonstrated in small rooms, its applicability towards larger rooms of different types is tested. Frequency dependency is also unknown and is investigated.
Localization to verify the identification of individual sperm whales using click properties.
Authors: Ioup Juliette W. , Ioup George E. , Pflug Lisa A. , Tashmukhambetov Arslan M. , Tiemann Christopher O. , Bernstein Alan , Sidorovskaia Natalia A. , Schexnayder Philip , Newcomb Joal J. , Kuczaj Stan A. , Rayborn Grayson H. , Carlson Rowena M.
Published: October 2013

Previous research to identify individual sperm and beaked whales from the properties of their echolocation and coda clicks using cluster analysis has been reported. Although reasonably consistent and robust results showing distinct classes (each corresponding to an individual) have been obtained with both self-organizing maps and K-means, no independent verification of these identifications has previously been available. However, data from a July 2007 experiment in the Gulf of Mexico should provide enough geometry information to verify some identifications. The Littoral Acoustic Demonstration Center deployed six environmental acoustic recording system buoys, measuring to 96 kHz for 9 days, to record sperm and beaked whale clicks in the northern Gulf of Mexico. Three buoys were in close proximity to enable multisensor detections of single clicks for possible localization, tracking, or bearing estimation sufficient to confirm the identification of individuals from cluster analysis. Displays of cluster classifications versus time coupled with location estimates for the clicks give evidence of the accuracy of the identifications. Though localization serves to verify the classification tool, click identification complements localization by separating sounds from multiple sources when several whales’ clicktrains overlap, potentially enabling previously impossible tracking. [Research supported by SPAWAR and ONR.]
Managing the passive acoustics data deluge.
Authors: Mann David A.
Published: October 2013

Passive acoustic recording systems can generate large amounts of data, especially given the increasing availability of inexpensive flash memory. Thus it is easy to collect more data than can be efficiently analyzed. One approach to this problem is to minimize data collection on the recorder by performing real-time automated detection of acoustic targets of interest. An alternate approach, where one does not know what signals may be present, is to record large amounts of data over extended periods of time. DSGlab is an open-source database and data analysis system implemented with MATLAB that is designed to manage large amounts of raw data. The database aspect of the program allows querying of data by latitude, longitude, depth (or altitude). Each recorded data file is tagged with header information including lat/lon/depth, timestamp, sample rate, and calibration. The data analysis section processes the files according to a user-specified signal processing chain, which does not require a knowledge of programming to generate, and returns results to a database and to individual files. The results of signal processing can then be quickly browsed with the data viewer. The system is designed to allow inter-laboratory collaboration and data sharing.
Probability density functions of modal amplitudes and complex acoustic pressure in fluctuating shallow water waveguides.
Authors: LePage Kevin D.
Published: October 2013

The polynomial chaos method is applied to the problem of predicting the probability density functions of complex modal amplitudes and acoustic pressure in the presence of water column sound speed fluctuations in shallow water waveguides. Results for both the intrusive implementation of the polynomial chaos technique, where the governing coupled mode differential equations for the complex modal amplitudes are augmented with the random states of the chaos expansion, and the non-intrusive method, where legacy codes can be run over an ensemble of ocean realizations and the results fitted by a truncated chaos expansion, are shown. Both methods give good agreement with Monte Carlo histograms of the modal amplitudes and the pressure field for slight water column variability, but the non-intrusive formulation shows more robustness for larger variability. The relative merits of PC expansions for the complex modal amplitudes vs the log amplitudes for the complex pressure amplitudes are also discussed.
Statistics of mode amplitudes in shallow water environments: Effects of random linear internal waves and nonlinear internal wave packets.
Authors: Colosi John , Morozov Andrey , Duda Tim
Published: October 2013

In shallow water environments there is presently an incomplete understanding of the relative acoustical importance of the random linear internal-wave field compared to nonlinear internal waves packets. Using the random coupled mode theory of [Creamer (1996)], the nonlinear internal wave mode coupling theory of [Colosi (2007)], and Monte Carlo numerical simulation we are able to demonstrate the important propagation physics when the two internal wave fields act alone, and simultaneously. Importantly, we find that for acoustic frequencies less than roughly 500 Hz and for propagation ranges of order 10s of kms mode propagation though the random internal wave field is very nearly adiabatic, and that cross mode coherences decay rapidly within the first 10 km. A surprising consequence of the decay of cross mode coherence is that the mean intensity will be to first order insensitive to nonlinear internal wave packets if they are located past the de-coherence range. It will also be shown that uncorrelated modes have important implications for the approach to saturation. The adiabatic nature of mode propagation though the random internal wave field may have important implications for shallow water acoustic remote sensing.
Ureteroscopic ultrasound technology to size kidney stone fragments: Proof of principal using a miniaturized probe in a porcine model.
Authors: Sorensen Mathew D. , Shah Anup , Canney Michael S. , Sapozhnikov Oleg A. , Teichman Joel M. H. , Bailey Michael R.
Published: October 2013

Background: the ability to measure stone fragment size could help prevent attempting to extract too large a stone fragment. We evaluated the ability of a 1.2 mm (3.6 French) ultrasound probe to measure stone fragments in a porcine kidney. Methods: 15 human stones of three types (five each calcium oxalate, cystine, calcium phosphate) sized 3–7 mm were placed deep in a porcine kidney collecting system. The sound speed of each stone type was determined using a separate reference stone. A 2 MHz, 1.2 mm needle hydrophone was used to send and receive ultrasound pulses. Stone thickness was calculated as d=c*t/2 by determining the signal transit time through the stone, t, and the stone sound speed, c. Calculated stone thicknesses were compared to digital caliper measurements. Results: Stone size was determined for all 15 stones. Correlation between ultrasound-determined thickness and caliper measurements was excellent (r2=0.90, p<0.0001) with ultrasound performing well in all three stone types. All stone measurements were accurate within 1 mm, and ten (66%) stone measurements were accurate within 0.5 mm. Conclusions: Ultrasound-based measurements are accurate and precise using a 3.6 French probe with stone fragments placed deep in a porcine kidney. [Work supported by Grants NIH DK43881 and NSBRI SMST01601.]
Kidney stone tracking in vitro using an acoustic triangulation paradigm.
Authors: Kracht Jonathan M. , Cleveland Robin O.
Published: October 2013

During shock wave lithotripsy, stones undergo motion which can place them outside the focal zone of the lithotripter. This results in shock waves being delivered that do not impact the stone but may injure tissue. Tracking stones using diagnostic ultrasound imaging (∼4 MHz) has proven to be challenging. Here we employed an array of seven relatively low-frequency (∼600 kHz) elements to detect scattered signals from an artificial kidney stone in the presence of a tissue phantom. Using an optimization routine, the time of flight to each element and array geometry were used to determine the most likely location of the stone. A comparison of threshold crossing and cross-correlation for detecting signal arrival indicated that while the former yielded faster computation time, the latter was more robust to noise. Stone position was determined to within 2 mm for locations within 10 mm of the focus. For distances beyond 10 mm, the optimization routine was not able to reliably predict stone location but could indicate that the stone was not within the focal region. [Work supported in part by NIH.]
Helmholtz resonator experiment for Project Listen Up.
Authors: Sparklin Marianne C. , Korman Murray S.
Published: October 2013

The behavior of sound waves and resonant effects can be observed using Helmholtz resonators. Resonators are built from identical round wooden boxes purchased from a craft store. The tops are glued and drilled with hole diameters from 2–3 cm. We can study the resonant behavior as a function of hole diameter only. The end effect is large compared with the thickness of the orifice (0.6 cm). In the experiment, a swept tone (100–900 Hz) from a small speaker drove the resonator. One studied the output of the microphone located near the orifice. One could use a swept spectrum analyzer, a function generator, or tuning fork with varying weights to measure the resonant frequency of the box. A plot of hole diameter versus frequency can be compared with the theoretical Helmholtz resonant frequency prediction, which depends on the volume of the box, the cross sectional area, the sound speed of air, and the effective length of the hole. One can model the effective length of the resonator as the thickness of the top plus a constant times the diameter of the hole and get good agreement with the established end correction found in textbooks.
The energy flow for a spherical acoustic lens: Ray and wave methods vs experiment.
Authors: Dean Cleon E. , Braselton James P.
Published: October 2013

A simple classroom demonstration consists of a weather balloon filled with carbon dioxide, a sound source, and a microphone. Since the speed of sound is slower in carbon dioxide than in air at room temperature and pressure, the balloon acts as a positive spherical acoustic lens. The accuracy of ray methods in locating the acoustic focus versus a full-blown wave solution approach has been presented previously [Cleon E. Dean and James P. Braselton, “The energy flow for a spherical acoustic lens: ray vs. wave methods,” J. Acoust. Soc. Am. 123, 3520 (2008).] Theoretically, this problem presents particular difficulties if the sound source lies in the near field region. The sound emitter is treated as a dipole source equivalent to a rigid oscillating sphere of small size and amplitude of motion relative to the scatterer. The energy flux around the balloon has been visualized by both ray methods and by the acoustic energy flux vector field. The geometrical ray results and the energy flux vector field resulting from the wave solution are compared with experiment.
Warning audibility in industrial accidents.
Authors: Erdreich John
Published: October 2013

Industrial accidents related to warning audibility may be adjudicated in the worker compensation environment or in state courts. One factor that may determine whether the incident becomes a compensation case or a tort is if the employer could reasonably expect the situation to require an audible warning. The second factor to evaluate is the adequacy of the warning itself. Thus, it is the responsibility of the acoustician to educate the trier of fact about not only the science of audition, but also the state of the art in that represents a consensus of methods to provide such warnings. An example of such a case will be presented.
Acoustic temperature measurement in a full-scale rocket noise field.
Authors: Giraud Jarom H. , Gee Kent L. , Ellsworth John E. , Thomas Derek C.
Published: October 2013

Acoustic pressure measurements in high-amplitude sound fields are common, but acoustic temperature measurements are relatively rare. This is primarily because thermometers exhibit thermal lag and, consequently, a limited frequency range. In this study, a 1 μ diam platinum wire resistance thermometer was used to measure temperature fluctuations generated by propagating noise produced by a horizontally fired, static GEM-60 solid rocket motor. The data are compared with those calculated from the pressure data of a nearby 3.18 mm condenser microphone by assuming an ideal adiabatic process.
Relative contributions of spectral and temporal cues for speech recognition in patients with sensorineural hearing loss.
Authors: Xu Li , Zhou Ning , Rife Katherine , Brashears Rebecca
Published: October 2013

The present study was designed to examine speech recognition in patients with sensorineural hearing loss (SNHL) when both temporal and spectral information in the speech signals were co-varied. Four subjects with SNHL were recruited to participate in consonant and vowel recognition tests that used speech stimuli processed through a noise-excited vocoder. The number of channels was varied between 2 and 32, which defined spectral information. The lowpass cutoff frequency of the temporal envelope extractor was varied from 1 to 512 Hz, which defined temporal information. Results indicate tremendously individual differences among the subjects with SNHL. For consonant recognition, patterns of relative contributions of spectral and temporal information were similar to those in normal-hearing subjects. The utility of temporal envelope information appeared to be normal in the hearing-impaired listeners. For vowel recognition, the performance plateau was achieved with numbers of channels as high as 16–24, much higher than expected, given that the frequency selectivity in patients with SNHL might be compromised. In order to understand how hearing-impaired listeners utilize spectral and temporal cues for speech recognition, future studies will be necessary to elucidate the relationship between frequency selectivity as well as central processing capability and speech recognition performance using vocoded signals.
Comodulation masking release and speech perception: Implications for dip-listening by cochlear implant patients.
Authors: Ihlefeld Antje , Shinn-Cunningham Barbara G. , Carlyon Robert P.
Published: October 2013

Compared to normal-hearing (NH) listeners, cochlear implant (CI) listeners struggle to identify speech when a source of noise interferes and do poorly when trying to listen in the dips of a modulated masker. In NH listeners, masker energy outside the spectral region of a target tone can improve target detection, a phenomenon referred to as comodulation masking release (CMR). Here we examined whether a comodulated flanking noise improves speech identification in a modulated noise masker, both for NH listeners identifying vocoded speech and for CI listeners. In experiment 1, NH listeners identified noise-vocoded speech (taken from a closed-set speech corpus) in a background of speech-shaped noise with or without a flanking narrow band of noise outside the spectral region of the target. The masker and flanker were either both 16-Hz square-wave modulated or were unmodulated. Performance was better in modulated than in unmodulated noise and, importantly, this difference was greatest when the comodulated flanker was present, consistent with the idea that CMR can introduce segregation cues between target and masker that help to listen in the dips of the masker. Experiment 2 tested CI listeners with the same experimental paradigm.
Determination of ultrasonic vibration modes of a graded solid cylinder using a modified wave-expansion technique.
Authors: Manzanares-Martinez Betsabe , Kim Jin-Yeon , Baltazar Arturo
Published: October 2013

Research on wave propagation in cylinders—hollow, solid, or graded—has been driven by its potential use in the inspection of long-span engineering structures. Its practical application largely depends on the understanding of modal vibration inside the structure. Typically, the plane wave approach is used to model phase velocity, group velocity and dispersion curves in periodic systems. This proves cumbersome when used to model finite periodic structures, semifinite plates, or concentric cylinders. Here, a simpler approach to determine the vibration modes and dispersion curves of a solid concentric cylinder using a modified wave-expansion approach, used mostly in phononic crystals research, is proposed. The advantage of this technique is the possible application on a wide variety of cylindrical geometries and graded structures with various transverse sections. The results of the proposed technique are compared with those obtained by the resonance scattering theory for the simple case of a solid cylinder with a single core having different mechanical properties. [Work partially sponsored by SEP-CONACYT through project # 58951.
Acoustic detection of bolt detorquing in structures.
Authors: Guarino Joe , Hamilton Robert
Published: October 2013

Recent interest in structural health of bridges and large buildings has lent new urgency to the development and enhancement of theories and methods in the field of nondestructive testing. We demonstrate a simple technique for acquiring data from an impact test using a basic electronic stethoscope. The continuous wavelet transform (CWT) is used to process and display the transient responses of a bolted joint in a structure with bolts installed in a properly tightened manner and bolts incorrectly installed. Results for tight and loose bolts are compared using the semblance analysis approach described by Cooper and Cowan [“Comparing time series using wavelet-based semblance analysis,” Computers & Geosciences 34, 95–102 (2008)]. We enhance the interpretation of results using speaker-driven audio output synthesized from CWT and semblance analysis.
Response of a simple system made complex by attaching subsystems—an analytic study.
Authors: McCoy John J.
Published: October 2013

A deceptively simple dynamical system comprised of a grounded mass to which are attached N, a large number, sprung masses has received much attention. The reported studies mostly involve physical experiments or numerical simulations. Given the large number of physical parameters needed to describe any single system, such a research agenda requires one to address an excessive number of experiment scenarios. Thus, the motivation for the analytical study reported. The focus of the study is the net force the attached subsystems cause to act on the base system. This force, while “internal” to the coupled system, is a response measure of primary importance since it accomplishes the work that determines the energy flow to and from the base system. As demonstrated, a further reason for the focus is an ability to construct an asymptotically valid, analytic expression for this response measure. Further demonstrated, using the constructed expression, is a resolution of a complex “process,” that describing the energy flow to the system, by the action of an external forcing, and through the system, as a combination of simple “sub-processes.” The resolution requires describing the complex process in a time/frequency phase space; the sub-processes are “local” in the phase space.
The epilaryngeal tube and air sacs in mammals as acoustic couplers—A review.
Authors: Riede Tobias , Tokuda Isao
Published: October 2013

The intralaryngeal space between glottis and the cranial edge of the larynx is called the epilaryngeal tube (synonyms are vestibulum larynges or supraglottal intralaryngeal space). Research on larynx models and in humans indicate that this part of the vocal tract filter can contribute to two important acoustic effects: (a) the singer’s formant and (b) the enhancement of nonlinear source-filter coupling. The acoustic role of this structure in nonhuman mammals is unknown. Furthermore, in many species tube and sac-like cavities are attached to the epilaryngeal tube (laryngeal air sacs) and their function is equally little understood. In this presentation I will report on results testing the hypothesis that the shape (length and diameter) of the epilaryngeal tube in nonhuman mammals is related to morphological parameters (vocal fold morphology, larynx size, body size) and parameters characterizing the species vocal repertoire (repertoire size, maximum sound amplitude, fundamental frequency range, occurrence of nonlinear phenomena). Preliminary results indicate that the length of the epilaryngeal tube is a poor predictor of repertoire characteristics such as maximum sound amplitude and fundamental frequency range. However, species with a prominent epilaryngeal tube produce a large proportion of high fundamental frequency call types.
Anisotropic bone loss characterized using fabric-based poroelasticity.
Authors: Cardoso Luis , Cowin Stephen
Published: October 2013

The current gold standard to assess bone loss is the bone mineral density (BMD) test, performed with a dual x-ray absorptiometry system. BMD measurements are highly correlated to bone mass when measured in spine, wrist, and femoral neck. However, the BMD cannot fully explain the decrease in bone strength and the associated risk of fracture because bone loss is not homogeneous, and does not depend on mass changes only. In this study, a fabric-based poroelastic model is used to determine the elastic constants of bone that have undergone disuse-osteoporosis and bone treated with an antiresorptive drug. Images from microCT are used to determine the porosity, density, and fabric on each group of specimens. These measurements are used in the proposed fabric-based poroelastic model to determine the sample’s anisotropic elastic constants. These elastic constants are then compared to the ones obtained by ultrasound wave propagation measurement as previously described in the Cowin and Cardoso presentation. Image analysis and ultrasound wave propagation are both shown able to determine changes in anisotropic elastic constants during bone loss when used with the proposed anisotropic poroelastic model. This study provides the foundation to define a bone quality criterion beyond the sole determination of bone mass.
Effective medium models from x-ray microtomography images.
Authors: Deffenbaugh Max , Dunsmuir John , Xu Shiyu , Liu Enru
Published: October 2013

A novel method is described where an effective medium model is generated from a 3-D x-ray microtomography image of a rock sample. In contrast to current modeling practice, material phases are not assigned idealized geometries, like spheroids. Instead, strain concentration tensors are computed numerically for the true phase geometries observed in the 3-D image. In this method, a 3-D image of x-ray attenuation is converted into a 3-D elastic properties volume, the strain field is computed within the volume, and the strain concentration tensors, which quantify the contribution of each grain and pore type to the bulk elastic properties, are calculated from the strain field. From only one representative sample of a rock type and with no assumptions about grain or pore shape, an effective medium model is generated that specifies the effective elastic tensor as a function of the various mineral and pore volume fractions. The method is demonstrated by generating effective medium models for several rock types. These models can be used in hydrocarbon exploration to relate the velocities of seismic waves in a poroelastic reservoir to the porosity, structure, and composition of the rock matrix and the type and distribution of the fluid within the pore spaces.
Geoacoustic inversion performed from two source-receive arrays in shallow-water waveguide.
Authors: Sukhovich Alexey , Roux Philippe , Wathelet Marc
Published: October 2013

Raylike propagation of acoustic waves in a shallow-water waveguide between two vertical line arrays is investigated by applying a double beamforming algorithm, which performs time-delay beamforming on both emitting and receiving arrays and allows identification of eigenrays by their emission and reception angles and arrival times. From the intensity of each eigenray, it is possible to determine reflection coefficient from the bottom of the waveguide as a function of an angle of incidence. The procedure was initially tested in a small-scale tank experiment for an acoustic waveguide with either steel or Plexiglas bottom. By fitting an experimentally found reflection coefficient with a corresponding theoretical expression, an estimate for the speed of shear waves in the bottom material was obtained. Similar analysis was subsequently applied to the data obtained during an at-sea experiment, which was performed between two vertical transducer arrays in shallow-coastal waters of the Mediterranean. An angle-dependent bottom reflection coefficient was extracted and geoacoustic inversion was performed by fitting the data with theoretical calculations, in which bottom sediments were modeled as a multilayered system. Good agreement between experiment and theory was observed. Our results indicate possible application of eigenray intensity analysis based on double beamforming algorithm for geoacoustic inversion problems.
Coherent backscattering effect from mid-frequency reverberation measurements in shallow-water.
Authors: Sabra Karim G.
Published: October 2013

The coherent backscattering (or backscattering enhancement) effect is a persistent interference effect which occurs between waves propagating in random media such as randomly distributed scatterers and rough surfaces. Previous experimental and theoretical studies in optics, acoustics, or seismology have demonstrated that the coherent backscattering results in a doubling of the recorded intensity reflected exactly in the backward direction with respect to any other direction. We will present experimental observations of the coherent backscattering effect from mid-frequency reverberation data (3–4 kHz) collected in shallow water off the west coast of Italy using various sensor array configurations. This demonstrates the presence of coherent effects in shallow water reverberation recordings from rough sea-beds. Hence, coherent reverberation effects need to be accounted for to obtain accurate predictions of sea clutter levels. Furthermore, accurate rendering of the coherent backscattering effect could be used to simply verify and validate physics-based undersea clutter models. Practical implementation for the design of active sonar systems will be discussed. [Work supported by ONR, Code 321.]
Modeling persistent clutter.
Authors: Newhall Bruce K.
Published: October 2013

Clutter is the collection of targetlike returns from nontarget sources that are observed in active sonar use. Persistent clutter is the set of clutter returns that persist across multiple transmissions and thereby form false target tracks in sonar processing. The U.S. Navy is developing active sonar simulators for training purposes. Effective training requires physically realistic clutter simulation including modeling of persistent clutter. Potential physical sources of persistent clutter are discussed, and a variety of modeling approaches are reviewed. Measures of effectiveness for model comparison with persistent clutter data are given.