bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel approach for overcoming effects of diffraction in measurements of the nonlinear B/A parameter in liquidlike media
Authors: Wallace Kirk D. , Holland Mark R. , Miller James G.
Published: October 2013

Finite amplitude measurements of the nonlinear B/A parameter in a liquidlike medium such as soft tissue can be complicated by the diffraction pattern associated with a bounded ultrasonic source. The goal of this work is to design and implement an approach based on the use of a stainless steel delay-line to position the specimen of interest either at the last axial maximum or in the far-field portion of the diffraction pattern from a piston source. A Burgers equation enhanced, nonlinear angular spectrum simulation was used to design the experimental apparatus by modeling the ultrasonic fields. A 0.6-mm-diam hydrophone receiver was mechanically scanned in a water-bath to measure the finite amplitude ultrasonic fields emerging from the delay-lines. A thin-plate tungsten resonator was used to suppress the fundamental relative to the second harmonic. As evidence of the effectiveness of this approach for overcoming complications of data analysis arising from diffraction, the nonlinear parameter B/A, the small-signal speed of sound, and the attenuation coefficient were successfully measured over a wide range of isopropanol-water mixtures. Measurements of B/A had an average uncertainty of less than 5% over the range of values associated with biological tissues (4.6 to 11.9). [Work supported by NIH R01HL72761.]
Average grain-size (g
s) estimation in polycrystalline channels
Authors: Hazony Dov , Katz J. Lawrence , Welsch Gerhard
Published: October 2013

Ample experimental evidence suggests that the impulse response of a polycrystalline channel is close to the Gaussian wave-form when the number of grains is sufficiently high. Moreover, a corresponding periodic cellular simulation of the channel, where each cell contains two reactive and one dissipative discrete elements, makes it possible to associate an impulse response-f(t)-with the model. It will be shown that also f(t) converges to the Gaussian waveform when the number of cells in the model is relatively large. Furthermore, it will be seen that, for the model to fit the channel, the cell-size must equal the average grain-size. It then follows that gs may be calculated from the variances of the incoming and outgoing signals and the respective delay between the first two waveforms. Data will be provided and a formula will be given. [Work supported by NIH.]
A comparison of optimized methods for the detection of blue whale sounds
Authors: Mellinger David K. , Heimlich Sara , Nieukirk Sharon
Published: October 2013

Paul Thompson and colleagues published one of the first long-term studies of mysticete sounds [Thompson and Freidl, Cetology 45, 1–19 (1982)]. Thompson analyzed sounds manually, finding and tallying vocalizations to arrive at a view of seasonal occurrence. Today the detection and counting tasks are often done by computer, using various methods for pattern recognition. Here we examine and compare three such methods for detecting the sounds blue whales: matched filtering, which may work well because of the stereotypy of blue whale vocalizations; spectrogram correlation, which may work well for the same reason and also because of the noise removal that can be done with it; and a neural network, which has worked well in other contexts for detecting right whale calls. The methods are configured using optimization procedures specialized for each method, and the results are compared for vocalizations recorded at different signal-to-noise ratios. The optimized detectors are applied to SOSUS data to detect sounds characteristic of blues whales in the northeast Pacific.
Single-crystal ferroelectrics for sonar devices
Authors: McLaughlin E. A. , Robinson H. C.
Published: October 2013

Single-crystal ferroelectrics or piezocrystals were recently introduced into the electroactive materials community. The 33-mode electromechanical coupling factor of piezocrystals is typically greater than 0.90, which is significantly larger than typical values for piezoelectric ceramics (0.62–0.74). For sonar projector applications this large, k33 has been responsible for more than doubling the bandwidth of active sonar arrays over what is currently achievable with ceramics. More recently, a crystal grower produced a cut of lead magnesium niobate-lead titanate (PMN-PT) single crystal with piezoelectric shear coefficient values of 7000 pm/V and shear coupling factors of 0.97. (For PZT5H, d15 is 730 pm/V.) This piezocrystal d15 coefficient implies significantly improved sensitivity and signal-to-noise ratio for accelerometers and hydrophones, while the high coupling promises bandwidth increases greater than those realized in 33-mode projectors using piezocrystals. The 31-mode is also being investigated. By measuring the response of the materials to high- and low-level electrical bias and excitation fields, mechanical prestresses, over temperature, the material’s effective material properties as a function of these operational variables have been determined. [This work sponsored by ONR and NUWC ILIR.]
Modeling the nonlinear string body coupled dynamics of bowed musical instruments
Authors: Inácio Octávio , Antunes José
Published: October 2013

Most theoretical papers on bowed-string instruments deal with isolated strings, pinned on fixed supports. In addition, the instrument body dynamics has not been accounted at all, or else by using extremely simplified models of the string/body interaction at the bridge. Such models have, nevertheless, been instrumental to the understanding of a very common and musically undesirable phenomenon—the ‘‘wolf note’’—a strong beating interplay between string and body vibrations. Cellos, bad and good, are prone to this problem. In previous work we developed a modal method to deal with friction-excited strings, enabling effective simulations of such systems in which the strings were assumed decoupled from the instrument body. In the present paper our computational method is extended to incorporate the complex dynamics of real-life instrument bodies, coupled to the string motions. In this approach, the string is coupled with experimental body data—body modes or impulse response at the bridge. Our computational method is illustrated through extensive parametric computations performed on a bowed cello. These numerical simulations show some light on interesting and less-known features of wolf notes, in particular concerning the ranges of bowing-parameters leading to their emergence, as well as the dependence of the beating frequency on the playing.
Why do non-native speakers have a foreign accent? A three-dimensional perspective
Authors: Shah Amee P.
Published: October 2013

A three-dimensional perspective, following the speech-chain model, is taken in arriving at the variables that influence the production and perception of foreign-accented speech. Essentially, research to date indicates the interactive role of all three communication components of the speech-chain model. First, speech-related variables, i.e., the interlanguage differences in the phonetic patterns of the speech, of L2 speakers compared to the L1 speech patterns influence listeners perception of accentedness of non-native speech. Second, speaker-related variables (i.e., differences in age, other psychological variables) cause the non-native speakers to have difficulties in learning to map new sounds of the L2 onto their existing L1 phonetic system, thus resulting in foreign-accented speech patterns. Lastly, differences in listener-related factors (i.e., L1 of the listener, prior linguistic experience, amount of exposure, listening-conditions in which they hear the accented speech) have been found to influence the perception of foreign-accentedness of speech. Past and current findings will be brought to bear upon this issue that has implications in theoretical understanding of speech perception, as well as practical applications in accent-modification and ESL classroom training programs.
Obtaining optimal time-delay, source localization and tracking estimates in free space and in an ocean waveguide
Authors: Makris Nicholas C. , Ratilal Purnima , Zanolin Michele , Bertsatos Ioannis
Published: October 2013

Asymptotic methods for obtaining optimal time-delay, source position and track estimates are derived for measurements in free-space and in an ocean waveguide using nonlinear statistical inference theory. The methods are useful for determining necessary conditions on controllable variables such as signal-to-noise ratio and sample size to attain desired design error thresholds. For free-space time-delay estimation, it will be shown both analytically and intuitively that the matched filter cannot be unbiased and attain minimum variance unless the kurtosis of the signal’s energy spectrum exceeds the signal-to-noise ratio [Naftali and Makris, J. Acoust. Soc. Am. 110, 1917–1930 (2001)]. In an ocean waveguide, it will be shown that signal-to-noise ratios and sample sizes necessary to attain practical localization error thresholds can become prohibitively large when random waveguide inhomogeneities such as internal waves degrade intermodal coherence.
Concurrent visual and acoustic tracking of fin whales offshore Southern California
Authors: Wiggins Sean M. , Sauter Allan W. , Hildebrand John A. , Abawi Ahmad T. , Porter Michael B. , Hursky Paul , Calambokidis John
Published: October 2013

Ocean acoustic techniques can be used to monitor whale presence within a region over long time periods. However, using the number of recorded calls to provide an estimate of the number of total whales present has not yet been realized. To help provide a transfer function from the number of acoustic calls to the number of whales present, we conducted a 10-day, concurrent visual and acoustic experiment aboard the FLoating Instrument Platform (FLIP) focusing primarily on fin whale monitoring. FLIP is a stable platform with a visual observation deck approximately 25 m above the sea surface providing excellent visual range. Suspended beneath FLIP at 90 m below the sea surface was a 105-m-long acoustic array consisting of 8 hydrophones, 15 m apart. FLIP was placed in a stationary 3-point mooring centered above three seafloor-mounted hydrophone recorders at depths between 250 and 400 m. The FLIP vertical and seafloor horizontal arrays provide excellent geometry for acoustically tracking whales via arrival-time difference and model-based techniques. These fin whale call tracks are compared to the visually observed fin whale surfacing to provide call-to-whale relationships.
Calculation of repetition rates of the vocalizations of killer whales
Authors: Brown Judith C. , Hodgins-Davis Andrea , Miller Patrick J. O.
Published: October 2013

A large number of whale sounds recorded from the Captive Killer Whale Population at Marineland of Antibes, France have recently been classified into call types using acoustic input and visual examination of spectral patterns [A. Hodgins-Davis, ‘‘An Analysis of the Vocal Repertoire of the Captive Killer Whale Population at Marineland of Antibes, France,’’ thesis, Wellesley College, 2004]. The repetition rate of the pulsed component of an example of each call type has been calculated using algorithms which have proven successful for pitch tracking of musical signals [J. C. Brown and B. Zhang, J. Acoust. Soc. Am. 89, 2346–2354 (1991), J. C. Brown, J. Acoust. Soc. Am. 92, 1394–1402 (1992)]. A new method based on pattern recognition of the Fourier transform has been the most successful of these methods as it best circumvents the problem of background pump noise. Results will be presented and compared. [Sound recording supported by grants from WHOI’s Ocean Life Institute and the Royal Society.]
Localization and tracking techniques for navigation and guidance of underwater autonomous sensing systems
Authors: Lee Hua
Published: October 2013

The key to the successful execution of autonomous underwater imaging and sensing is the localization and tracking of the data-acquisition units, which can be achieved by estimating the relative location with respect to a set of underwater base stations. In a three-dimensional underwater acoustic localization, the objective parameters are the range distance and a two-dimensional bearing angle. At the base stations, the transmitters send a sequence of guidance waveforms. One signal is a pair of polarity signals, with a 180° left–right phase offset, for the estimation of the bearing angle in the horizontal direction. Similarly, another one is with a top–bottom polarity for the estimation of the bearing angle in the vertical direction. The received signals represent spatial-temporal samples of the interferences produced by the polarities of the transmitted signals. The range distance can be estimated from the slope of the phase profiles of the spectra. And the bearing angle is directly related to the variation of the complex amplitude of the received polarity signals and can be estimated accordingly. This paper includes system design, signal analysis, development of processing algorithms, and results from full-scale experiments. [Research is supported by the UC MICRO program and Sonatech.]
Acoustic system for aircraft detection and tracking based on passive microphones arrays
Authors: Caronna Gaetano , Roselli Ivan , Testa Pierluigi , Barbagelata Andrea
Published: October 2013

The present study is conducted within a project included in the Sixth Framework Program of the European Union. The project, whose acronym is SAFE-AIRPORT, involves the development of an acoustic system based on two passive phased array microphone antennas, which are to be located in open environments, and capable of detecting and tracking airplanes at a distance in air and on ground. Each antenna array is made up of a series of microphones arranged on a rotating planar support. The Array’s spatial selectivity is discussed, aiming to optimize beamforming design according to spectral properties of common jet aircrafts. In particular, the influence of the number and the geometric distribution of microphones is shown in function of the target’s acoustic frequency and signal-to-noise ratio sensitivity. The system’s range is estimated at different working frequencies and for different positions of the aircraft on the horizon. The effect of wind gradients on the estimation of the aircraft position is also modeled, and computer simulations showing consequent deviation of acoustic waves are performed. Finally, possible developments in antenna design, such as the use of three fixed planar arrays in tetrahedral configuration instead of one rotating planar array, are evaluated showing expected advantages.
A verification of computer modeling predictions of speech intelligibility
Authors: Bowden Erica E. , Rathsam Jonathan , Wang Lily M.
Published: October 2013

Computer modeling has become a popular tool in the field of architectural acoustics to predict the acoustical characteristics of a built environment. One characteristic commonly investigated in computer models is speech intelligibility. This project compares speech intelligibility measures of the speech transmission index (STI), the rapid speech transmission index (RaSTI), and the articulation loss of consonants (ALCons) predicted by computer models to measurements taken in existing spaces. Three spaces in the Omaha, NE, area of varying size and function are analyzed: a theater, church, and classroom. Research methodology and conclusions are presented. The results aid in understanding the reliability of 3D computer modeling in speech intelligibility predictions. [Work partially supported by the Univ. of Nebraska Center for Building Integration.]
Vocalizations of Equus caballus: Frequency analysis of horse whinnies
Authors: Browning David G. , Scheifele Peter M.
Published: October 2013

There are six recognized horse sounds: scream, squeal, nicker, whinny, snort, and blow. Of these whinnies are the most interesting with a high enough source level for communication, perhaps being the horse equivalent of a bark, and a characteristic change in frequency content during the vocalization. This frequency variation is not observed in many farm animal vocalizations, cows, goats, and sheep, for example. An analysis is made of the variation in typical horse whinnies in order to identify any general characteristics as well as any specific variations that can be identified with specific behavior.
Diel periodicity of fish sound production in Charlotte Harbor, Florida
Authors: Locascio James , Mann David
Published: October 2013

Diel periodicity in sound production of spawning aggregations of fishes was documented in Charlotte Harbor, Florida from 7 May 2003–10 June 2003. The Long Term Acoustic Recording System (LARS) recorded 10 s of sound every 10 min within the frequency range of 0–1250 Hz. Field data collected in this study revealed diel patterns in fish sound production in great detail. Autocorrelation results demonstrated pronounced diel periodicity in fish sound production with significant lags occurring at 24-h periods. Chorusing events dominated by sand seatrout, Cynoscion arenarius, lasted for several hours each night and were not highly variable in duration, maximum recorded SPL, or start and end times. Mean daily (24-h period) maximum sound-pressure level was 119 decibels, mean daily chorus start time was 17:26 h Eastern Standard Time, mean daily chorus end time was 02:10 h Eastern Standard Time, and the average nightly chorus duration lasted 8 h and 43 min.
Acoustic modifications in choral reading
Authors: Poore Meredith A. , Ferguson Sarah H.
Published: October 2013

Choral reading is the condition in which one or more talkers read an assigned text aloud and in synchrony. Choral reading has several practical and theoretical applications, including use with beginning readers to enhance oral literacy, with people who stutter to evoke fluency, and as a tool for investigating speech rhythm. However, little is known about the speech acoustic modifications that occur when talkers perform the task of choral reading, or how different methods of eliciting choral reading may affect these modifications. In stuttering therapy, choral reading is usually elicited in pairs, either with two live talkers (choral reading) or one talker live and one prerecorded (track reading). While previous studies have assumed that these two reading conditions are equal, a recent study on speech timing suggests otherwise [F. Cummins, ARLO 3, 7–11 (2002)]. Measurements of pitch, amplitude and vowel duration will be compared across solo, track and choral reading of texts which vary in their perceived rhythmic organization. Acoustic data will be interpreted in reference to various theories regarding the effectiveness of choral reading for fluency enhancement. [Work supported by a University of Kansas Honors Program Undergraduate Research Award.]
A new invariant method for instantaneous source range estimation in an ocean waveguide from passive beam-time intensity data
Authors: Lee Sunwoong , Makris Nicholas C.
Published: October 2013

A new method is derived for instantaneous source range estimation in an ocean waveguide from passive beam-time intensity data received on a horizontal or vertical line array. While the method is as simple and robust as the ‘‘waveguide invariant’’ method described by Brekhovskikh and Lysonov (2003), it does differ significantly from the latter. Some advantages are that (1) it only requires source signal measurement at a single rather than many ranges so that range can be instantaneously estimated, and (2) it is invariant over all horizontally stratified ocean waveguides. The paramter β of the waveguide invariant method, on the other hand, varies significantly with vertical sound-speed structure. Since the invariant parameter of this new method varies only with the geometry of the array, the term ‘‘array invariant’’ method is here introduced. The method does not rely on near-field processing techniques but is also applicable at arbitrary far-field ranges. The method is applied to data from the Main Acoustic Clutter Experiment 2003 for source ranges between 2 to 10 km, where it is shown that simple, accurate, and efficient source range estimates can be made using this new method.
Hybrid joint probability density functions for active sonar
Authors: Gelb James M. , La Cour Brian R.
Published: October 2013

Methods are presented for estimating joint probability density functions (PDFs) of statistically dependent features with a focus on sparse data with planned application for computing likelihood functions for feature-based target classification in active sonar. The estimators involve a new class of hybrid models, i.e., adjusted combinations of low-dimensional, nonparametric PDFs and high-dimensional, multivariate, parametric models. One goal is to preserve physically meaningful feature identity. The efficacy of the methods to model PDFs and to classify data sets using these PDFs will be presented for simulated and actual data. Two general forms for the PDFs are presented: (1) hybrid models, Πipi(fi)[MN(f)/ΠiMi(fi)], where f represents a set of N features; pi(fi) are the marginal probabilities, and MN(f) is a model for the N-dimensional multivariate PDF with model marginals Mi(fi). (2) Expansion models: the multivariate PDF is expanded in terms of its correlations, Πipi(fi)[1+Σi<jξij+Σi< j<kζijk+⋅⋅⋅], with, for example, the two-point correlation functions defined as ξij=pij(fi,fj)/pi(fi)pj(fj)−1. In both cases successes and failures of the models and necessary modifications to them are presented to improve their general utility. [This work is funded by the ONR.]
Multisensor registration for distributed active sonar systems
Authors: La Cour Brian R. , Johnson Kevin , Quach Son
Published: October 2013

A technique is described whereby discrepancies between and biases within active sonar receivers may be corrected using acoustic signals. The method utilizes information contained in the direct blast recorded on each receiver over multiple active pings to estimate the ranges and bearings of the one or more sources relative to each receiver. Each sensor is assumed to have limited beamforming capability. In addition, the use of known acoustic scatters to resolve sensor misalignment will be discussed. Finally, results of an application of these techniques to active sonar data from the Deployable Experimental Undersea Multistatic Undersea Surveillance system (DEMUS) will be discussed and used to assess the algorithm. [This work was funded under ONR Contract No. N00014-00-G-0450-21.]
An underwater acoustic detection experiment based on forward scattering in a time reversal mirror
Authors: Stevenson J. Mark , Tesei Alessandra , Guerrini Piero , Boni Pierangiolo , Roux Philippe , Song Heechun , Hodgkiss William S. , Kuperman William A. , Akal Tuncay
Published: October 2013

Following earlier work by Song et al. [IEEE, J. Ocean. Eng. 28, (2003)] we conducted an underwater acoustic barrier experiment based upon forward scattering in a time reversal mirror. The experiment was conducted at a carrier frequency of 15 kHz in a shallow water waveguide. The waveguide length was about 16 water depths with one interface being an undulating, soft seafloor. After establishing a focus at one end of the waveguide, stationary and moving objects were placed in the water column, including an autonomous undersea vehicle (AUV). Before and after comparison of the received acoustic signal, including the temporal and spatial abberation of the focus, provided object detection. Several anomaly detection techniques were applied to the acoustic data in post-processing. Target speed was observed to be a discriminator in anomaly detection performance, suggesting that a combination of different anomaly detection techniques is probably desirable in addressing the moving target problem. [Work supported by NATO and ONR.]
Examination of bit error characteristics due to a drifting source in passive phase conjugation underwater acoustic communications
Authors: Yoon Jong R. , Park Kyu-Chil , Rouseff Daniel
Published: October 2013

Recent experimental work in acoustic communications using passive phase conjugation has shown that the demodulation error depends on the relative drift rate between the transmitter and receiver [Rouseff et al., IEEE J. Ocean Eng. 26, 821–831 (2001)]. The observed effect involves the mismatch between the initial impulse response and the subsequent response after the source or receiver has changed locations. The result can also be interpreted in terms of the spot size of the retro-focused field. In the present work, the effect of relative drift between source and receiver is studied by numerical simulations. The communications bit error rate is quantified as a function of drift rate, carrier frequency, array geometry and source-receiver range. [This work was supported by Pukyong National University Research Abroad Fund in 2003.]
Hair cell transducer design based on optical fiber Bragg gratings
Authors: Guillot Francois M. , Trivett D. H. , Rogers Peter H.
Published: October 2013

The development of a biomimetic transducer that reproduces the sensing mechanism of a single hair cell is presented. When light from a broadband source is input into an optical fiber terminated by a Bragg grating, the undisturbed grating reflects a fraction of the incident light at the Bragg wavelength, and the corresponding light intensity can be measured by a photodiode. The end of the fiber onto which the grating is written is adhered to two spacers separated by a 1-mm gap, and this assembly is adhered to two plates connected by a hinge, which is located below the gap. One plate is held rigidly and the tip of the other (free) plate experiences transverse vibrations, when ensonified. These vibrations induce longitudinal strains in the length of the fiber situated over the gap. Each unstrained portion of the grating reflects a small amount of light at the Bragg wavelength, resulting in two interfering light signals. The strain modulates the interference signal and produces an ac voltage at the photodiode output. The characteristics and performance of the transducer are presented, and its applications as the building block for underwater vector and tensor sensors are discussed. [Work supported by ONR.]
High-resolution spatial auralization techniques for room acoustics design
Authors: Henderson Paul D. , Torres Rendell R. , Pieleanu Ioana N.
Published: October 2013

Historically, consultants have avoided the use of computed auralizations when evaluating critical architectural design components due to uncertainties in the physical validity and perceptual accuracy of simulations. This work demonstrates the use of advanced techniques for increasing the confidence of auralized results, applied to the acoustical design of the Experimental Media and Performing Arts Center (EMPAC), currently under construction at Rensselaer. The 1200-seat performance hall in this facility contains an acoustically transmissive overhead canopy, which creates potential difficulties for conventional simulation techniques, specifically in the modeling of early reflected and transmitted sound paths. To overcome these challenges, a new ray-tracing engine was developed which introduces a ray-spawning method in the search for deterministic sound transmission paths in the early impulse response. In addition, this method allows for surface reflection and transmission characteristics to be defined with both arbitrary frequency resolution and with dependence on incidence angle. The resulting early-part simulations are coupled with statistically computed late reverberation. These auralizations are then rendered using second-order Ambisonics over a dodecahedron loudspeaker array, recreating a full-sphere sound field for the listener. In addition, the in situ localization performance of human subjects using this rendering system is reviewed. [Work supported by EMPAC at Rensselaer Polytechnic Institute.]
Functional-differential-equation models of reverberant energy decay in systems of coupled rooms
Authors: Summers Jason E.
Published: October 2013

Statistical-acoustics (SA) models of reverberant energy decay in systems of coupled rooms conventionally represent energy densities of subrooms as solutions of systems of coupled ordinary differential equations. These models unrealistically assume that exchange of energy between subrooms is instantaneous. Lyle has proposed a functional-differential-equation (FDE) SA model in which travel time of energy between subrooms is incorporated as constant delay times estimated from distances between centroids of adjacent subrooms [C. D. Lyle, Acoust. Lett. 4, 248–252 (1981)]. Here, an FDE-SA model is proposed which more generally accounts for travel-time distributions and, further, incorporates previously introduced improved decay models within subrooms [J. E. Summers et al., J. Acoust. Soc. Am. (in press)]. Monte Carlo methods are used to estimate travel-time distributions for simple geometries and allow for predictions with the FDE-SA model. Comparison of scale-model measurements and predictions of a computational geometrical-acoustics model with those of SA models shows that, contrary to Lyles findings, FDE-SA models must consider more than first moments of travel-time distributions in order to yield more accurate predictions. [This work was supported by the Bass Foundation.] a)Current address: Acoustics Division, Naval Research Lab, Washington, DC 20375-5350.
Nonlinear oscillations of encapsulated gas bubbles in incompressible elastic media
Authors: Zabolotskaya E. A. , Ilinskii Yu. A. , Meegan G. D. , Hamilton M. F.
Published: October 2013

An equation derived previously to describe nonlinear bubble oscillations in incompressible elastic media [Emelianov et al., J. Acoust. Soc. Am. 115, 581 (2004)] is modified to include an elastic shell with properties that are different from those of the host elastic medium. The new model equation is derived using Lagrangian mechanics. Nonlinearity is taken into account in the motion of the shell and surrounding medium, the compression of the gas, and the strain deformation in both elastic media. Two cases are considered for small but nonlinear bubble oscillations. The first applies to the case in which the equilibrium gas pressure is equal to the pressure at infinity, such that there is no equilibrium strain deformation in the medium. In this case, the Landau strain energy expansion can be used to obtain explicit expressions for the nonlinearity coefficients. For the second case, the equilibrium gas pressure in the bubble is different from the pressure at infinity, which results in strain deformation of both the shell and surrounding medium in equilibrium. Linear and nonlinear characteristics of the bubble oscillations are estimated for both cases. Limiting forms of the results are compared with those obtained by others. [Work supported by ARL:UT IR&D.]
Wave interaction on acoustic resonators with and without hysteresis
Authors: Ostrovsky Lev A.
Published: October 2013

Nonlinear interaction of counterpropagating waves in solids is considered by using a general approach taking into account only the cumulative effects for which the corresponding terms in the equations give nonzero contribution at a wave period. Different stress–strain relations are accessed, including those with hysteresis which serve as basic models for the recent acoustic experiments with rock and metals. It is shown that the model of a ring resonator interaction considered earlier is applicable for calculating the response of a resonance bar used in the majority of recent experiments. In particular, the ratio of the hysteretic dissipation coefficient and the relative sound speed variation due to nonlinearity remains independent on the amplitude. However, the nonlinear wave distortions and, hence, harmonic generation, occurs differently from that in a traveling wave.
Ultrasonic wave propagation in human cancellous bone: Application of Biot theory
Authors: Fellah Zine El Abiddine , Chapelon Jean Yves , Lauriks Walter , Depollier Claude
Published: October 2013

Ultrasonic wave propagation in human cancellous bone is considered. Reflection and transmission coefficients are derived for a slab of cancellous bone having an elastic frame using Biot’s theory modified by the Johnson et al. model for viscous exchange between fluid and structure. Numerical simulations of transmitted waves in the time domain are worked out by varying the modified Biot parameters. The sensitivity of each physical parameter used in the theory has been studied in transmission. Some parameters play an important role in slow wave waveform, such as the viscous characteristic length and pore fluid bulk modulus. However, other parameters play an important role in the fast wave waveform, such as solid density and shear modulus. We also note from these simulations that some parameters, such as porosity, tortuosity, thickness, solid bulk modulus and skeletal compressibility frame, play an important role simultaneously in both fast and slow waveforms compared to other parameters which act on the waveform of just one of the two waves. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.
Acoustic techniques provide insights into reproductive strategies of bearded seals, Erignathus barbatus
Authors: Van Parijs Sofie M. , Clark Chris W.
Published: October 2013

Several pinniped species mate underwater. This makes it difficult to study their mating behavior and assess their reproductive strategies. Acoustic techniques improve our capacity to study these species in their natural habitat. Captive studies demonstrate that vocal and dive displays are produced only by males. Studies of free-ranging animals demonstrate that these displays are produced during the mating season. Males have individually distinct vocalizations. In the Norwegian Arctic, male bearded exhibit two strategies, with some males holding small discrete territories within which they display and others roaming over much larger areas. In Alaska, data from an acoustic array were used to explore male behavior over 18 years. Males exhibited long-term site fidelity. In the Norwegian Arctic, fjord systems leave large ice-free areas within which males establish territories. In Alaskan waters, male movements and strategies are influenced by fast ice cover.
Application MEMS microphones in photoacoustic instrumentation for bio-chemical detection
Authors: Pedersen Michael
Published: October 2013

In this paper we discuss the design and application of MEMS-based microphones in photoacoustic (PAS) instrumentation, and it is demonstrated that by tailoring the properties of the microphone, tremendous improvements can be achieved in performance of particular importance to photoacoustic detection, such as sensitivity and noise level. Microphones typically used for PAS applications have bandwidths that exceed the requirements by an order of magnitude or more. New microphone designs, with bandwidths specifically targeted towards PAS applications, are shown to have open-circuit sensitivities in excess of 400 mV/Pa and noise levels around 0 dB SPL for a microphone diaphragm as small as 1×1 mm. This gain in performance may lead to a 10×–100× reduction of the detection limit in a state-of-the-art photoacoustic cell. Since the diaphragm in the MEMS microphone is very small, the mass of inertia is also greatly reduced, which leads to a reduction in vibration sensitivity of >10 dB over miniature hearing aid microphones and >20–30 dB over measurement microphones. The reduced vibration sensitivity is critical to push photoacoustic instruments from the laboratory into the field, where high performance rugged instruments are needed for bio-chemical detection.
Ultrasonic tissue characterization of the beating hearts of mice: Evidence of anisotropy and of hypertrophy
Authors: Miller James G. , Kovacs Attila , Posdamer Stephanie H. , Wallace Kirk D. , Courtois Michael R. , Weinheimer Carla J. , Holland Mark R.
Published: October 2013

New insights into the disease-altered properties of the heart may be provided through the study of genetically manipulated mice. To extend methods developed for studies of the hearts of patients to the hearts of mice, we report the observation of anisotropy of backscattered ultrasound in the parasternal short-axis view of normal mouse hearts, the cyclic variation of backscatter in normal hearts, and alterations of that pattern of cyclic variation in hypertrophic hearts. Echocardiographic images were obtained using a clinical imaging system with a nominal 13-MHz linear array. In seven wild-type mice the anisotropy of mid-myocardial apparent backscatter arising from the angle of insonification relative to the local fiber orientation in the short-axis view was consistent with that observed previously in the hearts of healthy human volunteers. The magnitude of the cyclic variation of backscatter from the hypertrophic hearts of nine mice subjected to neonatal aortic banding was significantly less than that obtained from eight control, sham-operated mice. This study lays the groundwork for subsequent investigations in which genetically manipulated mice will be measured in order to clarify the mechanisms of altered ultrasonic scattering and attenuation of the disease-altered myocardium in the presence of myocardial anisotropy. [Work supported by NIH R37HL40302.]
Effects of spectral tilt on the perception of naturally spoken vowels
Authors: Hillenbrand James M.
Published: October 2013

Experiments using synthetic signals with static spectral patterns have shown that spectral tilt can have an influence on vowel identity that is independent of the formant-frequency pattern [e.g., M. Kiefte and K. Kluender, J. Acoust. Soc. Am. 109, 2294–2295 (2001)]. The purpose of this experiment was to determine whether spectral tilt affects vowel identity for naturally spoken utterances. Test signals consisted of filtered and unfiltered versions of 300 /hVd/ utterances selected from a large, multi-talker database [Hillenbrand et al., J. Acoust. Soc. Am. 97, 3099–3111 (1995)]. Phonetically trained listeners (N=24) identified the unfiltered signals and the same signals conditioned by a +9 dB/oct filter and a −9 dB/oct filter, presented in a single random order. The effects of the two filters were clearly audible to listeners, but there was no effect of spectral tilt on vowel recognition accuracy. These findings do not invalidate earlier results with synthetic speech; rather, they suggest that when natural cues to vowel identity are preserved, overall spectral tilt plays little if any role in vowel recognition (within the limits of the ±9 dB tilt manipulation). The findings would also seem to present a significant challenge to whole-spectrum models of vowel perception, though they are by no means incompatible with this approach. [Work supported by NIH.]
Perceptual similarity co-existing with lexical dissimilarity
Authors: Weber Andrea , Cutler Anne
Published: October 2013

The extreme case of perceptual similarity is indiscriminability, as when two second-language phonemes map to a single native category. An example is the English had-head vowel contrast for Dutch listeners; Dutch has just one such central vowel, transcribed [E]. We examine whether the failure to discriminate in phonetic categorization implies indiscriminability in other—e.g., lexical—processing. Eyetracking experiments show that Dutch-native listeners instructed in English to ‘‘click on the panda’’ look (significantly more than native listeners) at a pictured pencil, suggesting that pan- activates their lexical representation of pencil. The reverse, however, is not the case: ‘‘click on the pencil’’ does not induce looks to a panda, suggesting that pen- does not activate panda in the lexicon. Thus prelexically undiscriminated second-language distinctions can nevertheless be maintained in stored lexical representations. The problem of mapping a resulting unitary input to two distinct categories in lexical representations is solved by allowing input to activate only one second-language category. For Dutch listeners to English, this is English [E], as a result of which no vowels in the signal ever map to words containing [ae]. We suggest that the choice of category is here motivated by a more abstract, phonemic, metric of similarity.
Computational model of modulation detection by the bullfrog
Authors: Simmons Andrea M. , Eastman Kyler
Published: October 2013

Bullfrog eighth-nerve fibers operate as envelope detectors, showing significant phase-locking to amplitude modulation (AM) rates as high as 800 Hz. A computational model that estimates stimulus period from all-order interval histograms (autocorrelation functions) aligned in time across frequency channels mimics fiber responses. The use of autocorrelation implies a mechanism based on delay lines or neural coincidence detection. The goal of this study was to determine the relevance of such a model in predicting responses of neurons in bullfrogs auditory midbrain (torus semicircularis) to AM stimuli. Modeled output of peripheral fibers was passed through a series of delay lines varying in latency, and then compared with actual midbrain data. There is a great diversity in representation of AM in the auditory midbrain, and this diversity is related to response latency and recording location. Neural responses from the cell sparse zone in the caudal midbrain were well-matched by a delay line mechanism, although the model was poorer in predicting response properties of other midbrain areas. [Work supported by NIH and the Brown University Brain Science Program.]
Finite element analysis of airflow in the vocal tract with lateral channels
Authors: Zhang Zhaoyan , Espy-Wilson Carol Y.
Published: October 2013

Lateral channels are airflow paths around the tongue produced by the laterally inward movement of the tongue toward the midsagittal plane during American English /l/ sound production. If contact is made with the palate, a closure is formed in the flow path along the midsagittal line. The closure is normally formed in the anterior part of the oral cavity and is about 1–1.5 cm long. However, it is speculated that the flow may split at a location posterior to the closure, thereby giving a longer length of the lateral channels up to 3–4 cm. Lateral channels of length around 3 cm have been shown to have significant effects on the resulting sound spectrum. To investigate the flow and acoustic field involved, finite element analysis was performed on a simplified model of the vocal tract during lateral sound production. The tongue was modeled as a rectangular constriction with a tapering slope on the upstream side and two flow channels on its two sides. The results show that the rising up of the tongue causes the flow to split into three regions of different flow amplitude and phase: one main region above the tongue surface and two regions around the tongue. This flow splitting occurs at the point where the tongue first begins rising up, well before the actual constriction location. The effective length of the lateral channels is therefore much longer than the length of the lingual constriction.
Inferring the vertical turbulent diffusion coefficient from backscatter measurements with a multibeam sonar
Authors: Weber Thomas , Bradley David , Culver R. Lee , Lyons Anthony
Published: October 2013

A 240 kHz multibeam sonar was deployed on a sub-surface mooring in order to collect acoustic backscatter measurements from the bubbles in a ships wake in August, 2002. The sonar was located at a depth of 30 m and oriented so that its swath of beams was orthogonal to the ships track. Measurements proportional to the acoustic scattering cross-section per unit volume were made and used to estimate the vertical turbulent diffusion coefficient in the ships wake using the same methodology that Thorpe used with a single-beam echosounder underneath breaking waves [J. Phys. Ocean. 14, 855–863 (1984)]. The wake was viewed as a distributed source of bubbles that are transported downward from the surface by turbulence. A steady state representation of the bubble field was used, where it was assumed that the bubble population exponentially decayed with depth, and that a bubble conservation equation could be written that only accounted for turbulent diffusion, buoyancy, and gas dissolution. Estimates of the vertical turbulent diffusion coefficient in the wake of a research vessel will be presented. [Work supported by ONR Code 321US. First author supported by a National Defense Science and Engineering Graduate Fellowhip.]
Time-reversal super-resolution and stability in a weak scattering medium
Authors: Jones Christopher D. , Berryman James G.
Published: October 2013

The properties of super-resolution and stability in time-reversal focusing of an acoustic wave are investigated using perturbation theory in a finite scattering medium with weak sound-speed fluctuations. Although super-resolution is obscured by weak scattering of the coherent field, the incoherent field still shows time-reversal enhanced focusing and the analytically tractable results may provide physical insight into time-reversal in stronger scattering media. Using first-order perturbation theory, the correlation scales of focused time-reversed field are defined by the scales of the fluctuations in the medium, the scale of effective aperture of the time-reversal array due to scattering and boundary conditions, the bandwidth of the system, and the array geometry. In this weak scattering example analytic expressions for the first and second moments of the time-reversal Green’s function operator are found and provide physical insight into the mechanism of time-reversal focusing and the role of bandwidth in super-resolution and stability. Numerical simulation using discrete point scatterers are performed to compare with the analytic results and to investigate the transitional behavior of time-reversal focusing from weak to stronger scattering.
Legal versus technical evidence of warning signal effectiveness
Authors: Fidell Sanford
Published: October 2013

A vast gulf separates technically from legally compelling proof. Attorneys (if not juries) crave deterministic certainty, simplicity, and self-assurance in expression of technical opinions, while scientists are more accustomed to discussing bandwidth-adjusted signal to noise ratios, working hypotheses, confidence intervals, and full disclosure of the limitations of data collection and theoretical interpretation. Given the many constraints imposed by the adversarial nature of civil litigation, presenting a jury with technically meaningful evidence about the effectiveness (or ineffectiveness) of acoustic warnings can be a formidable challenge. Favorable factual information and genuine expertise in interpreting it are helpful, but there are no guarantees that a jury can be persuaded that a technical opinion is correct.
Cochlear nonlinearity between 500 and 8000 Hz in listeners with impaired hearing
Authors: Lopez-Poveda Enrique A. , Plack Christopher J. , Meddis Ray , Blanco Jose L.
Published: October 2013

Cochlear nonlinearity was estimated in listeners with impaired hearing using a forward-masking method. For a fixed low-level probe, the masker level required to mask the probe was measured as a function of the masker-probe interval, to produce a temporal masking curve (TMC). TMCs were measured for probe frequencies from 500 to 8000 Hz, and for masker frequencies from 0.5 to 1.6 times the probe frequency. Unlike what happens for normal-hearing (NH) listeners [Lopez-Poveda et al., J. Acoust. Soc. Am. 113, 951–960 (2003)], TMCs for on-frequency maskers sometimes show a single slope, suggesting linear responses for tones at CF. Sometimes, however, two distinct slopes are visible, suggesting remaining compression. Both patterns are uncorrelated with the absolute threshold and are consistent with selective damage to outer or inner hair cells (IHC), respectively. Remarkably, the slope of the TMCs for very low-frequency maskers is shallower for the impaired ears than for normal ones. This result implies that for NH listeners, the slope of the TMCs for very low-frequency maskers reflects some kind of compression, even at high CFs. It is discussed that this compression is likely to occur at the IHC rather than at the basilar membrane. [Work supported by FIS PI020343, G03/203, and Oticon Spain.]