bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact directional acoustic sensing using multi-fiber optical probes
Authors: Bucaro Joseph , Lagakos Nicholas , Houston Brian , Dey Saikat , Zalalutdinov Maxim
Published: October 2011

A compact directional acoustic sensor concept is described, which uses an multi-optical fiber probe, a light emitting diode source, a photo-diode detector, and a short, slender cylindrical cantilever to the end of which is attached an optical reflector. A portion of the light exiting one fiber is collected by a second fiber after reflection from the mirror. Acoustically induced transverse displacement of the cantilever tip modulates the light collected by the second fiber, which then conveys the light to a photo-detector. Directional sensitivity is achieved by virtue of the dependence of the collected light on the cosine of the angle between the line connecting the probe fiber centers and the direction of displacement of the cantilever tip (the acoustic wave direction). An analytic model of the acoustic response of the cantilever tip is constructed, which is partially verified using a finite element-based model and experimentally validated using measurements of the acoustic response in air. The model is used to predict its acoustic response versus frequency, how that response depends upon damping near the cantilever resonance frequency, and to what extent and over what frequency band that response depends upon the acoustically generated flow force. [Work supported by ONR.]
Response surface optimization of a directional endfire microphone array for hearing aids
Authors: Burns Thomas
Published: October 2011

The optimal operating parameters for a directional microphone array worn in situ are not necessarily equivalent to the optimal parameters while operating in the absence of head and torso related scattering. These parameters include the relative magnitude and phase of the microphones and their positional placement on the head, characterized as factors, operating over a range of levels, characterized by their production spread and susceptibility to drift. The goal is to understand how these factors operating over their levels contribute to the in-situ directional responses on a measurement manikin, characterized by the directivity index and the unidirectional index. Using 614 impulse responses acquired in ten deg resolution on the manikin, a simple central composite design of experiments was conducted to fit a quadratic polynomial and generate a response surface to the aforementioned directional indices, thereby leading to the critical first-order and two factor interactions of the system. The interactions, statistical validity of the predictive polynomials, and the sweet spot of operation will be described for some common hearing aid microphone arrays.
Development of an optical transducer for an electro-acoustic guitar
Authors: Cho S. K. , Park Y. W.
Published: October 2011

This paper presents the development of an optical transducer (OT) for an electro-acoustic guitar. Two conceptual designs are proposed: one with one infrared light emitting diode (IR LED) and one photodetector, and the other with two IR LEDs and one photodetector. Both concepts are based on the top-to-bottom structure: IR LED is on the top, and the photodetector is at the bottom. After the preliminary tests, the latter design is selected as the proposed OT. The OT is fabricated on the PCB with proper electronic circuit, and mounted on the guitar. The developed OT is subjected to the performance evaluation with a dedicated measuring device. The performance of the OT is compared with commonly used piezoelectric transducer. Findings are summarized: (1) The output signals from the OT are much higher that those from the piezoelectric transducer in both average and peak-to-peak voltages. (2) The noise level from the OT is similar or less than that from the piezoelectric transducer. (3) SNR with the OT is increased by 45% in average, compared with the piezoelectric transducer.
Modeling and validation of magnetostrictive sound transducer including flat panel
Authors: Park H. J. , Park Y.W.
Published: October 2011

This paper contains models of the magnetostrictive actuator and flat panel for the investigation of interaction between actuator and flat panel. (1) A transfer function of the magnetostrictive actuator between a displacement Ua and input current I: Ga(s)=Ua(s)/I(s)=nd/(1+c/co+sr/co+s2m/co), where n is number of coil turns, d is magnetostrictive constant, c is stiffness of prestress spring, co is open circuit stiffness, r is damping coefficient, and m is effective mass. (2) Transfer functions of a flat panel: Gf(s)=Uf(s)/Ua(s)=−A/(−B+C+D),A=m1k1s2/(m1s2+c1s+k),B=m2s2+(c1+c2)s+(k1+k2),C=(c1s+k1)2/(m1s2+c1s+k1),D=(c2s+k2)2/(m3s2+(c2+c3)s+k2+k3), where m, c, and k are parameters of the actuator and flat panel models, and parameters are determined experimentally. The final transfer function of actuator and flat panel is expressed by multiplying Ga(s) and Gf(s). Simulations are performed through commercial program under the conditions applying a white noise to the final transfer function. The simulated and experimental frequency responses are compared.
Fourier: Making Waves—An interactive simulation for visualizing fourier analysis
Authors: Adams Wendy K.
Published: October 2011

In this presentation, the PhET simulation “Fourier: Making Waves” http://PhET.colorado.edu/en/simulation/fourier, will be presented including the research behind the simulation, how students react to it and ideas for use in class. Students typically learn the math needed to do Fourier transforms and learn how to express a function in time or space and in terms of wavelength, wave number, or mode. However, many of these relationships are only memorized for the short term (exam) and are not retained. This simulation is designed to help students visualize how a combination of simple sines and cosines can create a more complicated function and listen to the sounds produced by each harmonic. This simulation features 11 adjustable harmonics which can be used to demonstrate various auditory perceptions. There is also a game tab with ten different levels that challenges students to choose the correct harmonics to match more and more complicated functions. For more mathematical explorations, students can investigate each of the symbols lambda, T, k, omega, and n to learn what each represents on the graph and their relationships with one another. Finally there is a tab to help students visualize moving from a discrete to a continuous series.
Acousto-mechanical modeling of an Edison tinfoil phonograph
Authors: Sagers Jason D. , McNeese Andrew R. , Wilson Preston S.
Published: October 2011

A homemade reproduction of an Edison tinfoil phonograph was demonstrated at the 161st ASA meeting in Seattle, WA [JASA 129, 2581 (2011)]. While past work focused on the history and development of the device, the present work is focused on analyzing the acousto mechanical behavior of the homemade device. A dynamical model is presented and is used to predict the frequency dependent vibration of the phonograph diaphragm due to an acoustic input. The model predictions are compared with experimental measurements of the diaphragm vibration and potential solutions for optimizing the device are discussed.
Large-scale direct-test study reveals unexpected characteristics of absolute pitch
Authors: Deutsch Diana , Le Jinghong , Shen Jing , Li Xiaonuo
Published: October 2011

Absolute pitch, the ability to name a musical note in the absence of a reference note, is very rare in North America and Europe, so that attempts to characterize its features in the western world have involved small numbers of subjects, informal self-report, questionnaires, or web-based exploration. The study reported here capitalized on the high prevalence of absolute pitch in China to explore its features in detail using direct, on-site testing of 160 subjects in a Chinese music conservatory. As expected, performance levels were extremely high, and there was a large effect of age of onset of musical training, with those who began training by age 5 scoring on average 83% correct not allowing for semitone errors and 90% correct allowing for semitone errors. It was found that errors tended to be on the sharp side. An advantage to white keys over black keys was also found; however this was not due to early experience with the piano, as had been hypothesized by others, since performers on different instruments showed an effect that was as large or larger. Furthermore, the special status for note A that had been hypothesized by others was not found, even for orchestral performers.
The Instrument & the Room: A study of the grand piano focused on the needs of audio education
Authors: Leonard Brett , Sikora Grzegorz , de Francisco Martha
Published: October 2011

Through their training and education, aspiring recording engineers often encounter literature on the radiation patterns of typical musical instruments. The study of this information can greatly inform the placement of microphones and facilitate one's learning about the way acoustic instruments work. These musical acoustics studies, however, typically employ an anechoic or near-anechoic environment to minimize reflections from interfering with the instrument under test. Since the recording engineer works almost exclusively in environments with reflective surfaces, this causes a disconnect and can inhibit a full understanding of the relationship between the instrument and its environment. A case study of the acoustic grand piano is presented in which the instrument and the non-anechoic room are presented as a single, coupled acoustic system. Over 1300 measurement points are used to characterize the instrument/room combination. The study is conducted in both a small recording space and a large scoring stage, yielding non-room specific results that show areas of high frequency energy that are not present in typical anechoic measurements. Exploration of these differences and potential causes are presented.
Feature space minimization and its affect on head related transfer functions clustering
Authors: Andreopoulou Areti , Roginska Agnieszka
Published: October 2011

Several approaches have been taken toward data/feature-space reduction in HRIRs, operating either in the time (original, minimum phase, normalized HRIRs) or in the frequency domain (magnitude, log-magnitude, standardized log magnitude HRTFs). Shin and Park (2008) extracted only the response of the pinna (0.23 ms of the original HRIR), Hwang and Park (2007) included also the response of the head and torso (1.5 ms), while Bondu (2006) operated on the first 100 samples of the impulse responses. Other research focuses on employing PCA for minimizing the feature space to 5–12 orthogonal components and their corresponding weights (Langendijk, 2002; Huang, 2009; Hugeng, 2010), while others have managed to isolate directional and non-directional spectral cues of non-individualized HRTFs (Hu, 2008; Diepold, 2010). In previous work, the clustering tendencies of the standardized log-magnitude HRTFs of 110 subjects on the horizontal plane have been demonstrated, by applying k-means on 256-feature filters. In this study, those results are compared to the clustering behavior of data reduced filters by applying the previously mentioned techniques. The extent to which the original clustering tendencies are maintained is used as an evaluation criterion of the appropriateness of each data-reduction technique.
Effects of the soil on the noise attenuation of environmental berm barriers
Authors: Arenas Jorge P. , Alba Jesus , del Rey Romina
Published: October 2011

Berm mounds are a commonly used technique to reduce the environmental noise levels produced by highways. A berm is a natural noise barrier constructed of soil, stone, rock, or rubble, often landscaped, running along a highway to protect adjacent communities from noise pollution. An earth mound may be constructed using surplus materials at project site, provided there is sufficient land area available for its construction. Therefore, berms are natural environmental barriers, having relative low costs and they are subjectively well perceived by residents. However, exact noise attenuation provided by berms has not been enough explored in the technical literature, as opposed to common barriers made of vertical rigid walls. Although, some highway noise prediction models assign a noise reduction bonus of 3 dB(A) to sound barriers made of earth mounds, experimental assessments have yielded mixed results. Few theoretical reports have studied this particular problem. In this work, numerical analysis using the classical theory of diffraction is performed on a berm made of different types of soil. The model assumes a line source and includes flow resistant data as boundary conditions. By integrating the results, noise attenuation is given in third-octave bands. It is concluded that soil's properties significantly influence the measured results and that this may be one of the causes of varied in-site empirical evidence.
Hypersonic spectroscopy of porous silicon for acoustic devices
Authors: Snow Paul A. , Thomas Leigh-Anne , Goller Bernhard , Aliev Gazi N.
Published: October 2011

I will review our work on porous silicon (pSi) presenting achievements while highlighting underlying physical questions that remain to be answered. pSi is produced by the electrochemical etching of crystalline silicon. It is typically mesoporous, having pores of 10–30nm diameter. The etching current density determines the final porosity, the volume fraction of air, with a wide range of porosities, 25%–95%, achievable. For wavelengths much greater than the pore size, pSi gives a tunable effective medium for light and sound waves. We have characterized pSi acoustic properties using transmission spectroscopy with matched transducer pairs working at 0.5–2.5 GHz. The results for velocity, v, have fitted to a general law of v=v0(1−φ)k, where v0 is the velocity in bulk silicon, φ is porosity, and k is the fitting parameter. We have investigated the variation of k with the direction of propagation and the etching conditions used to extract the dependence of the elastic constants on porosity. The measurement of velocity has enabled us to produce and characterize pSi Bragg mirrors and rugate filters that have a smoothly varying acoustic impedance. This has demonstrated the potential use of pSi in acousto-optic phoxonic crystal devices that have both phononic and photonic bandgaps.
Probing acoustical, optical, and acousto-optical properties of nanostructured materials by picosecond laser ultrasonics
Authors: Gusev V. , Ruello P.
Published: October 2011

Research results on the characterization of the thin (submicrometers thick) films of the nanostructured materials by the experimental methods of picosecond laser ultrasonics are reviewed. These methods make use of femtosecond lasers to generate and to detect GHz–THz acoustic waves. In this communication, theoretical backgrounds of the fs-laser-based opto-acousto-optic techniques that are used for the evaluation of the material properties are first introduced. Then, the results of the experiments on nanoporous low-k films (for the microelectronics), on nanogranular sol–gel optical coatings (for laser optics), on anodized alumina (for the nanomaterial/nanostructure templates), on synthetic opals, on nanoparticles supra-crystals, and other nanostructured materials are discussed. The emerging opto-acousto-optic technology for the depth-profiling of acoustical, optical, and acousto-optical properties of inhomogeneous transparent films with the nanometers scale spatial resolution is also presented.
High frequency soft phononics
Authors: Fytas George
Published: October 2011

Phononic crystals, the acoustic equivalents of the photonic crystals, are controlled by a larger number of material parameters. The study of hypersonic crystals imposes substantial demand on fabrication and characterization techniques. Colloid and polymer science offer methods to create novel materials that possess periodic variations of density and elastic properties at mesoscopic length scales commensurate with the wave length of hypersonic phonons and hence photons of the visible light. Polymer- and colloid-based phononics is an emerging new field at the interface of soft materials science and condensed matter physics with rich perspectives ahead. The key quantity is the dispersion of high frequency (GHz) acoustic excitations which is nowadays at best measured by high resolution spontaneous Brillouin light scattering. Depending on the components of the nanostructured composite materials, the resolved vibration eigenmodes of the individual particles sensitively depend on the particle architecture and their thermo-mechanical properties [T. Still et al., Nano Lett. 10, 3194 (2008)]. In periodic structures of polymer based colloids, the dispersion relation ω(k) between the frequency and the phonon wave vector k has revealed hypersonic phononic band gaps of different nature [T. Still et al., Phys. Rev. Lett. 106, 175505 (2011)].
Soil plate oscillator: Modeling nonlinear mesoscopic elastic behavior and hysteresis in acoustic landmine detection, Part II
Authors: Duong Dang V. , Korman Murray S.
Published: October 2011

An apparatus (SPO), designed to study flexural vibrations of a soil loaded plate, consists of a thin circular elastic clamped plate (and cylindrical wall) supporting a vertical soil column. A small magnet attached to the center of the plate is driven by a rigid AC coil (located coaxially below the plate) to complete the electrodynamic soil plate oscillator SPO design. The mechanical impedance Zmech (force/particle velocity, at the plate's center) versus frequency is inversely proportional to the electrical motional impedance Zmot. Measurements of Zmot are made using the complex output to input response of a Wheatstone bridge that has an identical coil element in one of its legs. Resonant oscillation measurements (with no soil) before and after a slight point mass loading at the center help determine effective mass, spring, damping and coupling constant parameters of the system. “Tuning curve” behavior of real Zmot and imaginary Zmot at successively higher vibration amplitudes exhibit a decrease “softening” in the resonance and an increase in the quality Q factor. A bilinear hysteresis model [T. K. Caughey, ASME, J. Applied Mech. Trans. 640 (1960)] predicts the tuning curve shape for this nonlinear mesoscopic elastic SPO behavior.
Controlling the response of an oscillator using a coupled set of satellite oscillators
Authors: Hughes Ronald G. , Maidanik Gideon
Published: October 2011

The response of a system comprised of multiple dynamic systems is analyzed. The results shown here are for the main or master oscillator in that system. The balance of the dynamic systems is designated as satellite oscillators. Controlling the response of the master oscillator is described in terms of the couplings to the master oscillator, the frequency distribution of the satellite oscillators, the loss factors, and the masses of those oscillators. The frequency distributions and masses of the satellite oscillators are specified via normalizations with respect to the resonance frequency and mass of the master oscillator in order to generalize the approach. It is shown that contrary to reported results by others, there is no requirement to optimize the frequency distribution of the satellite oscillators to maximize the control of the response of the master oscillator. Further it is shown that increasing the loss factor of the satellite oscillators beyond certain values does not bring further benefit in controlling the response of the master oscillator beyond a certain level, in fact, a saturation is reached. We describe the on-set of saturation in terms of the modal overlap parameter.
State transitions in the Duffing resonator excited by narrow band random noise
Authors: Lyon Richard H.
Published: October 2011

The Dufffing hardening spring resonator has the status of a canonical model for nonlinear vibrations. Over a limited range of excitation frequencies and depending on the degree of nonlinearity, it has three states of response to sinusoidal excitation, one of which is unstable. The system will remain stably in either of the other two states depending on the history of excitation: in a higher energy state for the frequency ascending and in the lower energy state for the frequency descending. When the sinusoidal excitation is replaced by narrow band random excitation, the author showed in a 1961 paper experimentally that the system could make transitions between these two states and argued that the fluctuating phase of the excitation would allow the source to inject or draw energy from the resonator allowing a transition from one state to the other. This presentation develops a dynamic model for the system that allows energy transmission between the source and resonator and an indicator of the state of response based on instantaneous impedance.
Improving automatic speech recognition by learning from human errors
Authors: Meyer Bernd T.
Published: October 2011

This work presents a series of experiments that compare the performance of human speech recognition (HSR) and automatic speech recognition (ASR). The goal of this line of research is to learn from the differences between HSR and ASR and to use this knowledge to incorporate new signal processing strategies from the human auditory system in automatic classifiers. A database with noisy nonsense utterances is used both for HSR and ASR experiments with focus on the influence of intrinsic variation (arising from changes in speaking rate, effort, and style). A standard ASR system is found to reach human performance level only when the signal-to-noise ratio is increased by 15 dB, which can be seen as the human–machine gap for speech recognition on a sub-lexical level. The sources of intrinsic variation are found to severely degrade phoneme recognition scores both in HSR and in ASR. A comparison of utterances produced at different speaking rates indicates that temporal cues are not optimally exploited in ASR, which results in a strong increase of vowel confusions. Alternative feature extraction methods that take into account temporal and spectro-temporal modulations of speech signals are discussed.
Automatic and human speech recognition in null grammar
Authors: Juneja Amit
Published: October 2011

The accuracy of automatic speech recognition (ASR) systems is generally evaluated using corpora of grammatically sound read speech or natural spontaneous speech. This prohibits an accurate estimation of the performance of the acoustic modeling part of ASR, since the language modeling performance is inherently integrated in the overall performance metric. Even though acoustic modeling accuracy for ASR can be evaluated on these corpora using a null grammar language model, the accuracy cannot be compared with human speech recognition (HSR) since human listeners cannot be asked to ignore grammar. In this work a null grammar speech corpus was collected for comparing HSR and ASR. The corpus was collected in a hemi-anechoic chamber using three different vocabulary sizes—1000, 5000, and 10000—in a quiet environment. Noisy speech files at different signal-to-noise ratios were generated by adding noise at different levels to the quiet speech recordings. Human listeners were employed to transcribe the recordings and their accuracy was compared with an ASR system under different vocabularies and noise levels.
Towards the recovery of targets from coarticulated speech for automatic speech recognition
Authors: Hosom John-Paul , Kain Alexander , Bush Brian
Published: October 2011

An HMM-based ASR system tested on phoneme recognition of TIMIT (accuracy 74.2%) shows substitution errors covering all distinctive-feature dimensions of vowels: front/back, tense/lax, and high/low. These vowel-to-vowel errors account for about 30% of all substitution errors. These types of errors may be addressed by recovering vowel targets (and, as a by-product, coarticulation functions) during ASR. The current work models observed trajectories using a linear combination of target vectors, one vector per phoneme. A sigmoid function (with parameters for slope and position) models the evolution of the trajectory. In accordance with the Locus theory, if duration is sufficiently short and the rate of change is sufficiently slow, the targets may not be reached. Current data indicate that in clearly articulated speech, the vowel target is often reached, while in conversational speech, the vowel target is often not reached. This difference between speaking styles may explain the difficulty that current ASR systems have in recognizing conversational speech: by not always reaching the vowel target, the observed values for a phoneme have higher variance and increased overlap with other phonemes. By recovering the target values, variance of phonemes within the feature space may be reduced, thereby improving classification accuracy. [Work supported by NSF Grant IIS-0915754.]
Solution behaviors of multistatic transmission loss equations
Authors: Shiba Hisashi
Published: October 2011

A sonar arrangement is one of the most important problems in the multistatic sonar. Although it is very useful to proceed numerical simulations for arrangements, they usually consume much computing resources and their results are sometimes difficult to grasp physical meanings. On the other hand, it is beneficial to analyze the acoustical field further from the classical sonar equation view point as a quick looking. One of the most important element is the transmission loss in the sonar equation. In the multistatic configurations, the transmission loss is dependent on the direction from a receiver. The transmission loss is usually notified as a function using transmitter parameters. New descriptions are introduced without transmitter parameters in this presentation. Spreading dominant cases produce quartic transmission loss functions of the target distance form the receiver. They are solved analytically; however, the solutions do not constitute Cassini oval in spite of some preceding researches. Absorption dominant cases are also solved analytically. Mixtures of spreading dominant and absorption dominant are not able to be solved analytically. These solution behaviors are easily surveyed by contour maps of the transmission loss. These maps are useful for sonar arrangements.
Time-varying filter estimation for the deconvolution of environmental reverberation from active sonar returns
Authors: LePage Kevin D. , Goldhahn Ryan
Published: October 2011

The estimation and removal of the time-varying two-way impulse response to environmental scatterers from broadband reverberation data is considered for increasing the signal-to-noise ratio of sonar returns from targets in the water column. Spectrograms of simulated and real reverberation time series data from active sonars in the mid-frequency range show strong evidence of interference patterns which give clues to the number of important paths to environmental scatterers as well as their depth in the water column. In this talk we consider the estimation of a time dependent de-convolution filter for the removal of these environmental reverberation returns from active sonar data. Issues regarding the degrees of freedom required for the efficient implementation of this filter and the stability of these estimates are considered. Simulation results are shown which demonstrate the potential gain of using this approach to partially null the impact of environmental scatterers in active sonar data.
The influence of suppression of side lobes on the range of passive sonars
Authors: Milosic Zvonimir
Published: October 2011

This paper presents a universal procedure of the de-embedding of mathematical functions of ratios of maximal ranges depending on the level of suppression of side lobes at the directivity pattern of passive sonar antenna. This dependence is founded on the specially made and named as “idealized model” of measured directivity pattern of a sonar antenna with the model of elliptical cross section of the main lattice perpendicular on acoustic axes. Using the given mathematical expressions of directivity index and dependence of suppression of side lobes at the mentioned idealized model of directivity pattern characteristics with equations of hydrolocations and their conditions, there are relatively simple expressions of ratio of maximum ranges in form of defined function mz. Using the given mathematical function mz there is possible to control the value of all important parameters for the de-embedding of the sonar ranges in its specification. In accordance with given model, there are point out the importance of ratio of ranges of maximum value of level of suppression of side lobes at directivity pattern characteristic with elliptical cross section of main lattice of antenna. Mainly, the level of suppression of side lobes is less than −50 dB at contemporary passive sonars today.
Experience with geoacoustic inversion of transmission loss
Authors: Vidmar Paul J.
Published: October 2011

This presentation will discuss recent experience with geoacoustic inversion of transmission loss (TL) data from 50 to 5000 Hz from both deep and shallow water regions. For shallow water, a multi-layered geoacoustic profile with range dependent layer thicknesses is used. Layer thickness is not an inversion parameter but is known from ancillary data such as seismic profiling and chirp sonar. Issues related to range dependent sound speed profiles (SVPs) will be discussed as will observation of the time spread of multipath arrivals. For deep water, a single layer geoacoustic profile is assumed. Quality of inversion is assessed using comparison of measured and modeled TL and the estimation error. The estimation error is the dependence of the total rms error—summed over range, frequency, and receivers—on the values of a geoacoustic parameter within the bounds used to constrain inversion. The estimation error identifies geoacoustic parameters that are well constrained or poorly constrained by the TL data. Inversion was carried out using a genetic algorithm model [D. Harvey et al., Oceans '02 MTS/IEEE, 1, 358–362 (2002)]. Acoustic and environmental data were provided by the Naval Oceanographic Office. [Work funded by the Ocean Bottom Characterization Initiative through PEO C4I, PWM 120.]
Comparison of parabolic equation and coupled mode solutions to seismo-acoustic problems
Authors: Frank Scott D. , Odom Robert I. , Park Minkyu , Collis Jon M.
Published: October 2011

Parabolic equation methods that use the single scattering approximation and improved rotated coordinate methods generate accurate and efficient solutions for range-dependent underwater acoustic problems with elastic sediments. Recently these methods have demonstrated the conversion of acoustic energy in a fluid into shear propagation in an underlying elastic layer. Elastic coupled mode theory can also be used in a range-dependent environment and provides an accurate description of the conversion between fluid and elastic modes during propagation. The current parabolic equation approach will be augmented with an elastic version of the self-starter that includes both compressional and shear wave energy. Results from these two approaches will be compared for acoustic and elastic sources in both range-independent and range-dependent underwater environments. Propagation at the fluid–solid interface will be examined as a possible mechanism for the conversion of elastic layer shear energy into acoustic energy in the water column. An elastic source is used to demonstrate that sources of this type can transmit substantial acoustic energy into the water column. [Work supported by ONR.]
Time-evolving T-phase arrival structure using simultaneous recordings by large-aperture horizontal and vertical line arrays in PhilSea09
Authors: Freeman Simon E , D'Spain Gerald L. , Steven Ralph , Heany Kevin D. , Baggeroer Arthur , Worcester Peter , Mercer Jim , Lynch Stephen , Murray Jim
Published: October 2011

A number of models have been proposed to explain the mechanisms by which seismic phases couple to the deep ocean sound channel in order to create water-borne acoustic tertiary (T) phases. Beamforming conducted on simultaneous recordings by large-aperture horizontal towed and vertical moored line arrays during PhilSea09 shows the temporal evolution of a T-phase arrival consistent with the down-slope modal conversion/propagation model. Towed array calibration is conducted using ship-deployed, controlled multi-tone acoustic sources. Conventional, minimum variance distortionless response, white noise constrained, and dominant mode rejection beamformers are compared in their ability to minimize bias and variance in estimating the azimuthal arrival directions of signals from both the controlled source and the seismic phases recorded by the horizontal array. Horizontal array beamformer-derived azimuth and time-of-arrival range estimates from P, S, and T-phase arrivals at towed and moored receivers indicate the event occurred in a region with appropriate bathymetric relief for down-slope conversion/propagation. The seismic event in question was not recorded by the USGS/NEIC seismometer network. This study thus further showcases the highly sensitive capabilities of in-water hydrophones and the effect of array gain to characterize high-frequency (5–50 Hz) seismic events. [Work supported by the Office of Naval Research.]
Orchestra canopies
Authors: Skalevik Magne
Published: October 2011

Looking around, one might get the impression that a canopy has become a “must have” in every new concert hall and a magic recipe in any refurbishment project. There are, however, cases where canopies would be unwanted, unnecessary, insufficient, inadequate, or even detrimental to the acoustics on stage or in the rest of the hall. Some of the highest rated concert halls among musicians and audience, Musikvereinsaal in Vienna, Concertgebouw in Amsterdam, and Boston Symphony Hall, all fail to have a canopy. Still, there are many halls where the use of a canopy is justified. This paper points at the importance of starting by defining the requirements to the acoustics on stage (and in the rest of the hall), and then the question how these requirements could be met. A canopy may be the answer, maybe not. Significant features, acoustic properties, design issues, and parameters for prediction and measurements of canopy performance will be discussed. In short: Orchestra canopies—what difference can they make?
Venting full-stage portable acoustical shells: The acoustic impact on the stage and audience environments
Authors: Freiheit Ron
Published: October 2011

The effectiveness of acoustical shells in the stage acoustic environment has long been a topic of discussion. Generally, their impact is positive with increased gain (G) both on stage and to the audience area. However, there has also been speculation that containing too much energy on stage negatively impacts clarity (C80). A study was conducted of an installed portable shell that provided an option to vent energy to the backstage area, thus providing the potential to reduce the overall energy in the stage area. Impulse responses were measured in a number of areas on stage and in the audience area, with vents both open and closed. The results of those metrics will be presented. Binaural recordings were also made at the same locations, providing perceptual information as well.
Fine-tuning onstage acoustical elements to satisfy... Whom?
Authors: Jaffe J. Christopher , Sacks Jonah , Markham Benjamin E. , Berens Robert S.
Published: October 2011

Movable onstage features such as over-stage reflector panels, acoustical shell towers, reverberant chamber doors, seating risers, etc. offer a high degree of variability and control over ensemble balance, loudness, and other parameters. Finding the optimal settings for such features is far from trivial and combines many different considerations: quality of sound to the various audience seating sections, balance and intelligibility of the ensemble to the conductor, self and ensemble hearing for the various instrumental sections, and overall loudness onstage, to name a few. On the occasion of welcoming Maestro Christoph Eschenbach as its new Music Director, the National Symphony Orchestra scheduled a special acoustical rehearsal for the purpose of exploring the range of available settings of the adjustable over-stage reflector panels at the Kennedy Center Concert Hall. The presentation will include a detailed description of the rehearsal and the adjustments made to the reflectors, the authors' observations and findings, and various conclusions that have been drawn. Particular attention will be paid to the range of reactions and feedback from various participants, including the Maestro, musicians in different sections on stage, symphony administrators and musicians listening from the audience, and the authors.
Passive acoustic recording to build acoustic catalogs to remotely monitor resident individuals and the health of the dolphin population in the Indian River Lagoon system in Florida
Authors: Gerstein Edmund , Brady Beth , Weeks Rebecca , Bossart Gregory , Goldstein Juli , McCulloch Stephen
Published: October 2011

Harbor Branch Oceanographic Institute at Florida Atlantic University together with, NOAA's National Ocean Service/Center for Coastal Environmental Health & Biomolecular Research initiated a research program designed to assess environmental and anthropogenic stressors that may affect the health and long-term viability of bottlenose dolphin populations inhabiting coastal regions of Florida and South Carolina This collaborative program is known as the Health and Environmental Risk Assessment Project. The project involves the capture, sampling, and release of selected wild dolphin stocks to allow comprehensive health screenings by collecting and analyzing a variety of biomedical samples and associated data. During Indian River Lagoon (IRL) dolphin population assessment, the acoustic behavior of 33 individual dolphins was recorded using synchronized DARP buoys configured with directional and omnidirectional hydrophones. Vocalizations were recorded during the capture, holding and health sampling phases. Acoustic levels and behavior during ABR hearing measurements were also monitored. The whistle contours of 23 individuals have been identified and will be added to the photo-identification and genetic catalog maintained for the IRL population. These signature whistles will be used to train a network of remote acoustic sensors to monitor the distribution, social interactions, and habitat utilization of cataloged dolphins in the IRL. Authorized NMFS permit 14352-01.
New call type produced by the North Pacific right whale, Eubalaena japonica
Authors: Crance Jessica L. , Berchok Catherine L. , Clapham Phillip J.
Published: October 2011

The North Pacific right whale, (NPRW), is one of the most endangered baleen whales in the world and has been the focus of intensive population monitoring studies. In 2010 during transit through the Bering Sea right whale critical habitat (BSCH), near-24-h acoustic monitoring was conducted using DiFAR-capable sonobuoys. A new call pattern was detected during a focal follow of a NPRW, consisting of a series of pulses with a fundamental frequency at 110 Hz and peak energy at 640 Hz, ending in a 250–150 Hz downsweep. This call pattern was repeated multiple times and detected in the presence of gunshot and upsweep calls. Directional bearings to the call were a perfect match to those of the gunshot call. Although humpback whales were present, bearings to the humpback vocalizations were in the opposite direction (200 deg difference). The only other species detected visually or acoustically in the area were fin whales. This same pattern was detected in October and November on a 2009 long-term recorder in the BSCH, also in the presence of gunshot and upsweep calls. Because directional information from the sonobuoys during the focal follow exactly matched those from the gunshot call, we attribute this call pattern to the NPRW.
Passive acoustic and visual monitoring of humpback whales (Megaptera novaeangliae) in the Olympic Coast National Marine Sanctuary: Importance of quantifying call type
Authors: Cummins Amanda J. , Oleson Erin , Calambokidis John , Schorr Greg , Falcone Erin , Wiggins Sean , Hildebrand John A.
Published: October 2011

Humpback whales (Megaptera novaeangliae) produce a variety of vocalizations such as social and feeding calls as well as patterned calls that comprise song. Typically, social and feeding vocalizations do not follow the highly structural format of song. High-frequency acoustic recording packages were deployed in the Olympic Coast National Marine Sanctuary July 2004 through June 2009 while visual surveys were conducted throughout the year at approximately monthly intervals. Humpback whales were detected visually and acoustically; however, there was a mismatch in the peak seasonality of these detections. Visual detections occurred in all seasons but peaked in summer and early fall. Acoustic detections were documented primarily in late summer to early winter. Male humpback whales are known to produce long songs primarily during their winter breeding season. To test whether the detection differences between visual and acoustic surveys could be explained by changes in the whales' vocal behavior, we quantified the relative occurrence of song and non-song calling using a variety of metrics and related the occurrence to the visual survey sightings. We show how identification of the type of acoustic detection is an important consideration and can help address biases introduced by seasonal differences in the production rate of reproduction-related calls.
Production of shear waves with novel radiation force beams
Authors: Greenleaf James , Chen Shigao , Urban Matt
Published: October 2011

Propagating shear waves in tissue can be measured with high frame rate Doppler or correlation methods. The measured characteristics of the shear waves, such as speed versus frequency, can be used to deduce material properties such as complex viscoelastic modulus using physics models appropriate to the geometry and properties of the tissue. This inverse problem is characterized by calculating the storage and loss modulus as a function of frequency and requires appropriate tissue motion, which in turn requires optimized dynamic radiation force distributions. We will discuss novel radiation force distributions that provide enhanced tissue motions appropriate to dealing with the inverse problem of determining tissue material properties from ultrasonically measured tissue motion.
Acoustic radiation force applied to the treatment of lower pole kidney stones
Authors: Bailey Michael R. , Cunitz Bryan W. , Dunmire Barbrina , Wang Yak-Nam , Lu Wei , Simon Julianna C. , Kaczkowski Peter J. , Sapozhnikov Oleg A.
Published: October 2011

Lower pole kidney stones have lower rates of clearance after shock wave lithotripsy or ureteroscopy compared to other stone locations. Residual stone fragments, post treatment, often lead to additional morbidity and secondary surgery. We describe the use of acoustic radiation force created by transcutaneous focused ultrasound to manipulate the location of stone fragments within the collecting system in order to facilitate their passage. Artificial and human stones were placed in the lower pole of kidneys of a porcine animal model. An open architecture, software based diagnostic ultrasound system and scanhead were modified to produce roughly 100 μs pulses of up to 16 MPa peak positive pressure in water. Stone motion was observed in real-time with simultaneous imaging through the same scanhead and with fluoroscopy. All stones were seen to move. Stone velocities were on the order of 1 cm/s. Stone displacement distance was up to 3 cm, and operators could generally control the direction of stone movement. No evidence of thermal necrosis or mechanical damage of renal tissue was observed. Thus acoustic radiation force can be used to facilitate lower pole stone fragment clearance. [Work supported by NIH DK43881, DK086371, DK092197, and NSBRI through NASA NCC 9-58.]
On the numerical computation of the acoustic radiation force generated by a modulated sound field
Authors: Dontsov Egor , Guzina Bojan , Chen Shigao , Fatemi Mostafa
Published: October 2011

The acoustic radiation force (ARF), which signifies the average transfer of momentum from the sound wave to the propagating medium, is nowadays frequently used to compute the mean displacement field in soft tissues due to the action of a focused ultrasound beam. In situations when the sound field used to generate the ARF is modulated, the latter depends on both spatial and temporal derivatives of the acoustic intensity. Unfortunately, the numerical computation of the nonlinear acoustic solution due to modulated focused ultrasound beam is complicated by the presence of two disparate time scales in the formulation. To deal with the problem, the KZK-type spatial scaling is complemented by its dual-time-scale companion, where the temporal coordinate is split into its “fast” and “slow” components, allowing one to track the ultrasound-scale oscillations and modulation-scale variations separately in the solution. In this case, the nonlinear acoustic solution (and consequently the ARF) can be effectively computed in the “fast” frequency domain and “slow” time domain for any given modulation envelope, transient, or steady-state. The proposed developments are both validated by the experimental results and illustrated via numerical examples that show the effectiveness of the computational scheme.
The role of constitutive nonlinearities and sound modulation in the generation of the acoustic radiation force
Authors: Guzina Bojan , Dontsov Egor
Published: October 2011

This study investigates the acoustic radiation force (ARF) in soft tissues when the generating ultrasound field is modulated with a low-frequency envelope (102-104 Hz range). On approximating the soft tissue as that of a nonlinear elastic material with heat conduction and viscosity, the system of nonlinear balance equations, governing both the ultrasound-scale oscillatory motion and the ARF-induced mean motion, is formulated explicitly. To deal with the effects of ultrasound modulation, a dual-time-scale approach featuring the “fast” (ultrasound-scale) and “slow” (modulation-scale) temporal coordinates is deployed. In this setting the governing equations for the mean motion, featuring the ARF as the body force term, are extracted by taking the “fast” time average of the nonlinear balance laws. The ARF is shown to consist of two distinct terms, namely (i) the potential term, which is proportional to the gradient of the ultrasound intensity and (ii) the axial term, which contains both an attenuation-driven component and a modulation-driven component. A salient feature of the new solution for the ARF is that its entries feature specific combinations of the elastic nonlinearity coefficients, which may vary depending on tissue type. For completeness, the proposed formula is illustrated by numerical simulations and compared to the existing expressions.