bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcranial MRI-guided FUS-induced BBB opening in the rat brain
Authors: Treat Lisa H. , McDannold Nathan J. , Hynynen Kullervo
Published: September 2013

The blood-brain barrier (BBB) has been a major limitation in treating diseases of the brain because therapeutic agents are either unable to penetrate or have dose-limiting side effects in diffuse opening of the BBB. A previous study demonstrated that focused ultrasound (FUS) can locally open the BBB in a rabbit model when a piece of skull is removed and that magnetic resonance imaging (MRI) can be used to guide and monitor the procedure. This study examined whether the same desired effect of local BBB disruption can be achieved by applying FUS through an intact skull in a rat model. Twenty-eight Sprague-Dawley rats were anesthetized, shaved, and sonicated at four focal locations in the brain, using a 1.5-MHz focused transducer. Contrast-enhanced MR images were obtained before and after sonication. The images indicated contrast agent penetration at the focal coordinates following Optison-enhanced sonication. This study demonstrated that the distortion of the ultrasound beam by the rat skull was not significant enough to inhibit focal BBB opening. Subsequent experiments using MRI-guided FUS to aid in targeted drug delivery to brain tumors in a rodent model could thus be performed more efficiently without cranial surgery. [Research funded by NIH Grant No. CA76550.]
Development of local volume displacement sensors for vibrating plates
Authors: Wendt Ron , Zahui Marcellin
Published: September 2013

Development of local volume displacement sensors is presented. This development supports the implementation of noise control techniques that are based on minimization of local volume displacements, velocities, or accelerations of a vibrating structure. In this paper, a general methodology for the development of local volume displacement sensors for vibrating plates using PolyVyniliDene Fluoride (PVDF) is presented. This methodology was verified experimentally for a clamped plate. The local volume displacement measured using a PVDF sensor matched the local volume displacement found using multiple accelerometer measurements. The resulting sensor spans the entire length of the plate and covers the width of the area of interest. The sensor is composed of a number of strips whose width varies quadratically on the local area and linearly elsewhere. Design issues for a clamped plate, a simply supported plate, and a plate with arbitrary boundary conditions are discussed along with a presentation of some sample sensor shapes.
Effects of mutual impedance on the radiation characteristics of transducer arrays
Authors: Lee Haksue , Tak Jinhee , Moon Wonkyu , Lim Geunbae
Published: September 2013

The mutual resistance of transducer arrays is investigated in order to design arrays with improved performance for high intensity sounds at a given frequency. This work proposes the theory that the mutual resistance is related to the loading effects of pressure waves propagated from a piston driver on the surface of another driver. Using this interpretation, the important characteristics of the mutual resistance of two piston drivers are explained and the conditions for local maxima in the mutual resistance are easily determined. On the basis of analyses of the interactions between a driver and acoustic pressure waves, we propose a method to determine the driver radius and the distance between two drivers that give maximum mutual radiation resistance. To evaluate the proposed method, the total resistance of a transducer array is calculated using the formulas for mutual and self-resistance established by Pritchard. The results of the calculations of the total resistances of arrays with many drivers show that a transducer array with drivers arranged sparsely can achieve a larger value of the radiation power per unit area as well as better radiation efficiency than an array in which the drivers are in a closely packed arrangement at a given frequency.
Radiation control applied to sound synthesis: An attempt for ‘‘spatial additive synthesis.’’
Authors: Warusfel Olivier , Misdariis Nicolas , Caulkins Terence , Corteel Etienne
Published: September 2013

Sound synthesis is generally focused on the reproduction of the spectral characteristics of the source or on the simulation of its physical behavior. Less attention is paid to the sound playback step which generally results in a simple diffusion on a conventional loudspeaker setup. Stating the perceptual importance of a faithful reproduction of the source radiation properties, the paper presents a method combining a synthesis engine, based on physical modeling, with a rendering system allowing an accurate control on the produced sound-field. Two sound-field synthesis models are considered. In the first one, a local 3D array of transducers is controlled by signal processing for creating elementary directivity patterns that can be further combined in order to shape a more complex radiation. The dual approach consists in surrounding the audience with transducer arrays driven by wave field synthesis in order to simulate the sound field associated to these elementary directivity patterns. In both cases, the different radiating modes of a given instrument are synthesized separately, in conjunction with their associated radiation pattern, and then superimposed in the spatial domain, i.e., during the propagation in air. This approach, referred as ‘‘spatial additive synthesis,’’ is illustrated, taking the example of different musical instruments.
Recent concert halls and opera house in Japan
Authors: Hidaka Takayuki
Published: September 2013

Since we invited Dr. Beranek to Japan for the first time in 1989, we had been working together with him for a period of 13 years, until 2001, on seven hall projects as acoustic design consultants. All of these halls are of premium importance to Japan. Dr. Beranek always came up with innovative concepts and helped create halls endowed with high acoustic originality. These halls are now loved by music-related people and music fanciers and regarded as the pride of Japan. The reviews and studies achieved through these projects were published as seven J. Acoust Soc. Am papers to disclose the outcome in an objective way to the public. A brief outline of the history of our collaboration and its background are presented.
History of acoustical consulting at BBN
Authors: Wood Eric W. , Ungar Eric E.
Published: September 2013

A book is being written describing the history of acoustical consulting at Bolt Beranek and Newman Inc. (BBN). It highlights people that joined the firm during the early years, the unique culture they established, the major clients and projects, noteworthy contributions made by the staff, and 40 years later the transition of BBNs acoustical consulting practice to Acentech. The book is based on interviews of colleagues and friends, primarily by Deborah Melone, a former BBN editor. This presentation reviews the early days of the consulting partnership formed by Bolt and Beranek in 1948, its initial growth, and its achievements.
Demonstration by optical visualization of acoustic re-radiation from A0 and S0 waves on submerged shells
Authors: Raju P. K. , Ahyi A. C. , Cao H. , Überall H.
Published: September 2013

Elastic waves propagating on thin shells may be classified like for the Lamb waves on plates (A0, S0, A1, S1...), and the Scholte-Stoneley wave (A) in the fluid loading. The present study deals with evacuated shells of semi-infinite extent and a uniformly curved front surface, on which acoustic pulses are incident head-on. The incident signals cause the generation of the mentioned shell waves at a critical angle of incidence; these may be observed by their reradiation into the fluid at the same critical angle. Our demonstration of the reradiated pulses consists in a numerical evaluation of the incident and reradiated fields, and a visualization of the corresponding pulses in a tank experiment employing the Schlieren method. While the A wave could not be observed because of its rapid decay following its generation, we were able to demonstrate by both methods the generation of reradiated pulses of the A0 and the S0 wave, at the same time verifying the value of the critical angle of their generation.
Experimental and numerical investigation of flow through an oscillated acoustic resonator
Authors: Daniels Christopher C. , Finkbeiner Joshua , Steinetz Bruce M. , Athavale Mahesh , Pindera Maciej
Published: September 2013

An acoustic resonator was oscillated experimentally at the fundamental gas resonant frequency to develop standing pressure waves. The conical shaped resonator contained openings that provided an air passage from a pressurized cavity through the resonator to the ambient environment. For several pressure differentials applied across the resonator, the rate of air flow is reported for no resonator oscillation, and for on-resonant and near-resonant frequency oscillations. When compared to no oscillation and near-resonant frequency oscillation at all pressure differentials, the standing waves within the resonator reduced the flow of air through the system when oscillated on-resonance. A two-dimensional numerical model was developed using a commercial CFD package to simulate the gas flow within the system. The mass flow of air through the oscillating resonator was matched using the numerical simulations. For a low value of differential pressure, the simulations showed the reversal of gas flow into the high pressure cavity during a part of the cycle, while allowing free flow of air during other cycle phases. For a high value of differential pressure, no flow reversal was observed. The goal of the study was to determine the applicability of nonlinear acoustics to advanced seal concepts at NASA Glenn Research Center.
Localized mode of sound in a waveguide with a pair of Helmholtz resonators
Authors: Sugimoto N. , Imahori H.
Published: September 2013

This paper examines a localized mode of sound in a planar waveguide between rigid walls with a pair of identical Helmholtz resonators connected. Assuming the waveguide extends infinitely, a two-dimensional problem to the wave equation is solved within linear, lossless theory. By the localized mode are meant time-harmonic, stationary oscillations without radiation damping, which are confined only in the vicinity of the resonators and decay exponentially away from them. It is revealed that when the resonators are connected vis-à-vis to the upper and lower walls, an antisymmetric localized mode can exist but no symmetric mode exists. In the antisymmetric mode, the sound pressure changes out of phase π in the upper and lower half of the waveguide. In the dispersion diagram between frequency and wavenumber, the localized mode introduces an isolated frequency at vanishing wavenumber in addition to an infinite number of duct modes. The frequency of the localized mode is lower than the lowest cutoff frequency of the duct modes and also a natural frequency of the resonator. The solution for the localized mode is represented by superposition of an infinite number of antisymmetric, evanescent duct modes. When the resonators are staggered on both walls, the localized mode disappears.
Perceptual and procedural learning in interaural cue discrimination
Authors: Constantinides Helena , Moore David R.
Published: September 2013

Training in stimulus detection, discrimination, or identification generally leads to an improvement in performance, apparently in two phases. Learning during the early, rapid phase (within hours) has been attributed predominantly to procedural or task learning. Perceptual (true stimulus) learning is believed to occur mainly in the slower, later phase. Two experiments were undertaken to determine whether significant perceptual learning also occurs during the early phase. In the first, four groups of listeners were trained for 1 h in interaural level difference (ILD) discrimination. Stimuli were presented within a different, two- or three-interval task for each group. The following day, complete generalization of learning from the trained to the untrained tasks was demonstrated. In the second experiment, two groups of listeners were trained in an ILD discrimination task. In one group the stimulus was at a fixed, suprathreshold level (ILD=15 dB), and in the other the stimulus was varied adaptively around the listener’s discrimination threshold. The post-train mean stimulus discrimination threshold in the suprathreshold group was 3.9 dB, and in the threshold group was 2.4 dB (p<0.01). These findings suggest perceptual learning contributes significantly to the early, rapid phase of performance improvement in interaural cue discrimination.
Transmission loss of a submerged viscoelastic slab containing oblate spheroidal coated microinclusions
Authors: Haberman Michael , Berthelot Yves , Cherkaoui Mohammed
Published: September 2013

The three-phase self-consistent (SC) micromechanical model of Cherkaoui et al. [J. Eng. Mater. and Technol. 116, 274–278 (1994)] is employed to model the anisotropic effects induced by identically oriented coated ellipsoidal microinclusions embedded in a viscoelastic matrix. Numerical predictions of the lossy and anisotropic behavior of the viscoelastic composite material are obtained. This study is an extension of a previous paper [J. Acoust. Soc. Am. 112 (5), 1937–1943 (2002)], where the agreement of the micromechanical approach with the long wavelength scattering model of Baird et al. [J. Acoust. Soc. Am. 105 (3), 1527–1538 (1999)] was demonstrated. The use of the SC model for the special case of a biphase effective material is also considered and compared with the complex bounds given by Gibiansky and Lakes [J. Mech. Mater. 16, 317–331 (1993)]. Parametric studies are presented for the transmission loss in the 0–100-kHz frequency range of a 1-cm-thick composite material slab containing oblate spheroidal inclusions of varying aspect ratios when the slab is submerged under water. The results are compared with the case of a composite material having identical constituent material properties and volume fractions as the oblate case but containing spherical inclusions.
Prediction of the sound reduction index with the modal theory
Authors: Tisseyre Alain , Courne Cecile , Moulinier Andre , Buzzi Thomas
Published: September 2013

A procedure of sound reduction index calculation was developed on the basis of the modal theory. This calculation uses the study of the vibratory behavior and of the radiation of the plate. The vibratory study makes it possible to characterize the displacement of the wall. The latter is developed over a base: sinusoidal or polynomial. The use of a sinusoidal base makes it possible to obtain satisfactory results without limitation of frequency. In this case, the only possible boundary condition corresponds to a plate simply supported. The use of a polynomial base only makes it possible to obtain results in the low frequencies. On the other hand, in this case, several boundary conditions are possible: embedded, simply supported. In both cases, modeling several types of walls is possible: isotropic or orthotropic wall, single or multiple walls. Walls, orthotropic due to their geometry, were more particularly studied. It is the case in particular of alveolar slabs, bricks and ribbed sheets. A formulation of the acoustic transparency was established and programmed, and various results are presented. Currently, a calculation algorithm is developed in order to allow polynomial base modeling on a more significant frequency range.
Numerical solution of acoustic radiation from fluid-loaded periodic structures using local-global homogenization
Authors: Danilov Pavel V. , Bliss Donald B.
Published: September 2013

Fluid-loaded vehicle structures, such as fuselages and hulls, often have spatially periodic discontinuities such as braces, ribs, and attachments. The structural motion, the acoustic radiation and scattering, and the interior sound field are of interest. Calculating the motion of fluid-loaded structures is a difficult task because of the high complexity and a disparity of length scales requiring high numerical resolution. Discontinuities cause the structural response to occur in a broad spectrum of spatial wavenumbers, and to exhibit stop-band and pass-band behavior. Structural discontinuities broaden the spatial wavenumber spectrum, causing both supersonic (radiating) and subsonic (nonradiating) waves. An analysis method called local-global homogenization (LGH) is used to predict directly the low wavenumber smooth response of periodic fluid-loaded structures in a self-contained manner. The low wavenumber part of the response is efficiently coupled to the acoustic field, since low wavenumbers correspond to supersonic phase speeds. In the LGH reformulation, an infinite order operator that must be truncated for numerical solution governs the equivalent smooth global problem. The numerical implementation is described, including the treatment of boundary conditions, and sample calculations are compared to exact solutions. The size of the computational problem is dramatically reduced by the LGH analytical reformulation.
The effect of consonantal context on intensity distribution in vowels
Authors: Jacewicz Ewa , Fox Robert Allen
Published: September 2013

Overall vowel intensity varies intrinsically with vowel quality and in terms of immediate consonantal context. These variations affect the levels of formants F1–F4 and F0, which change in consonantal contexts according to a vowel−specific pattern [Jacewicz, J. Acoust. Soc. Am. 114, 2395 (2003)]. The current study further examines the differential distribution of acoustic energy across and within continuous frequency bands in the vowel as a function of vowel quality and consonantal context. The analysis technique used here was adopted from Sluijter and Van Heuven [J. Acoust. Soc. Am. 100, 2471−2485 (1996)], who measured differences in spectral intensity distribution across frequency bands as a function of stress. The intensity distribution of the vowels /i, i, ε, æ, u, u/ in American English were measured across eight frequency bands in a stressed [C1VC2] context (where C1=C2). Contexts were chosen which have the greatest (e.g., voiceless fricatives) and the smallest (e.g., voiced stops) effect on changes in relative amplitude of formant frequencies and F0 for each particular vowel. Preliminary results indicate that intensity variations across frequency bands as a function of consonantal context have a potential to change the overall spectral balance. [Work supported by NIDCD R03 DC005560−01.]
Formants of Japanese function particles
Authors: Shirai Setsuko
Published: September 2013

There is much debate about whether vowel centralization results from reduction of undershoot. The results of research conducted by Keating and Huffman (1984) indicated that Japanese vowels in prose were formed closer to the center of vowel chart than in words. However, they did not provide any statistical information and the information about the preceding consonants in the prose. Thus, there was a possibility that the preceding consonants led to the vowel centralization through undershoot. To address this question, I conducted research, in which Japanese function vowels [a, e, o] were compared with content vowels. The results showed that F1 of function /a/ following /g/ (average 609.8 Hz) was statistically lower than content /a/ (average 696.3 Hz) [F(1,65)=73.40, p<0.001]. However, there were no significant differences of F2 of /e/ following /d/ and F2 of /o/ following /t/ between function and content. At first, it appeared centralization played a role. However, close examination of the results indicated that vowel undershoot was the source of the /a/ centralization. Japanese function /a/ was statistically shorter than content /a/ and there was a significant correlation between duration and normalized vowel displacements for /a/ [Pearson’s r=0.466, p<0.001]. This short duration caused the difference of F1 between content /a/ and function /a/.
Co-articulation effects on sound /r/ in cluster words
Authors: Agrawal S. S. , Dhiman Deepak
Published: September 2013

In this study the coarticulatory effects on the formant frequencies of sound /r/, one of the most context dependent sounds of Hindi, have been investigated, by taking combinations of the cluster sounds of the forms C1r, rC2 and C3C4r. In these cluster combinations C1 is one of the consonants from (/k/,/p/,/g/,/t/,/d/,/m/,/n/,/h/,/bh/,/w/,/b/,/ph/), C2 is one of the consonants from (/y/,/ñ/,/th/,/t/,/∫/,/m/,/dh/,/k/,/w/,/n/,/g/,/j/,/bh/,/t∫/, /dz/,/ph/,/d/,/s/) and C3C4 is one of the combination from (/∫t/,/st/,/nd/,/n:r/, /ndh/). A database of 438 cluster words spoken by three male speakers has been prepared. The sound /r/ has been perceptually segmented from these utterances and the first three formants and their corresponding bandwidths have been measured. For C1r combination, the deviations of the formant frequencies become larger with the order of the formants. The deviations in the formants for rC2 case are also large and it is nasalized if C2 is some nasal sound like /ñ/ and /m/. For the third case (C1C2r), the formant frequencies do not deviate much as in the earlier two cases but the effect of the frication of the combination /∫t/ makes it fricative. These results are being used in improving the quality of Hindi Klatt Synthesizer.
Bimodal schwa: Evidence from acoustic measurements
Authors: Yamane-Tanaka Noriko , Gick Bryan , Bird Sonya
Published: September 2013

The question of whether schwa is targeted or targetless has been the subject of much debate (Browman et al., 1992; Browman and Goldstein, 1995; Gick, 1999, 2002). Gick (2002) found that there is a pharyngeal constriction during schwa relative to rest position, and concluded that schwa is not targetless. This experiment further showed a ‘‘bimodal’’ pattern in schwa in a nonrhotic speaker, indicating that the subject has distinct schwas in lexical words and function words. The present study examines the existence of the ‘‘bimodal’’ pattern in schwas in nonrhotic dialects through an acoustic experiment. It is predicted that there is a significant difference in formant values between lexical schwas and function schwas. Results to date indicate a significant difference in them between schwas in lexical versus function words, both between historical schwas and those derived from final /r/ reduction. Data from several additional nonrhotic subjects will be presented. Implications for intrusive r as well as for the phonological treatment of function words will be discussed. [Work funded by NSERC and SSHRC.]
Acceptability of variations in question intonation in natural and synthesized American English
Authors: Syrdal Ann K. , Jilka Matthias
Published: September 2013

In a previous study exploring American English question intonation, we found that some speakers deviated considerably from expected question prosody. In this study, we focus on listener-rated acceptability of the various prosodic patterns observed for yes/no and wh questions. A variety of intonational patterns realized in both question utterances recorded from five female and three male professional speakers and in questions synthesized from several TTS voices of both genders was presented to listeners. Subjects judged the acceptability of each utterance in the context of a dialogue between a travel agent and customer. We hypothesized that question utterances with the expected intonational features (phrase-final fall in wh questions, phrase-final rise in yes/no questions) would be rated as more acceptable than question utterances with deviating intonational features, and that this result would hold for both natural and synthetic speech conditions. In addition, following our previous results, we hypothesized that the unexpected intonation pattern of phrase-final falls for yes/no questions would be more acceptable for lower-pitched than for higher-pitched voices. We also varied the prominence of the interrogative pronouns in synthetic wh questions in order to see whether simulating their high intonational prominence in natural wh questions improved the acceptability of synthetic wh questions.
Obstruent-sonorant consonant sequences—Analysis by synthesis
Authors: Mou Xiaomin
Published: September 2013

The goal of this work is to develop principles of overlapping gestures in obstruent-sonorant sequences in the word-initial position and sonorant-obstruent sequences in the word-final position. Consonant clusters such as sm in small are phonetically represented as a sequence of individual elements, but the exact perceptual representation is unclear. The modification during the production of these overlapping gestures may be driven partly by perceptual salience and partly by vocal tract aerodynamics. When two consonants occur next to each other, the same gestures may be made as for only one consonant. The aerodynamics of the vocal tract may account for the modification in the timing of the articulators during production and this modification can be incorporated as rules into HLsyn, a higher-level quasiarticulatory speech synthesizer that takes as inputs the pressures and the flows of the vocal tract. Acoustic information extracted from the speech waveform is mapped into inputs for HLsyn. This analysis by synthesis approach is a method to develop a more precise picture of the planning stage during speech production where the acoustic phonetics must be carefully planned and modified to acheive the correct target sounds. [Work funded by a grant provided by NIH.]
Musical experience and Mandarin tone discrimination and imitation
Authors: Gottfried Terry L. , Staby Ann M. , Ziemer Christine J.
Published: September 2013

Previous work [T. L. Gottfried and D. Riester, J. Acoust. Soc. Am. 108, 2604 (2000)] showed that native speakers of American English with musical training performed better than nonmusicians when identifying the four distinctive tones of Mandarin Chinese (high-level, mid-rising, low-dipping, high-falling). Accuracy for both groups was relatively low since listeners were not trained on the phonemic contrasts. Current research compares musicians and nonmusicians on discrimination and imitation of unfamiliar tones. Listeners were presented with two different Mandarin words that had either the same or different tones; listeners indicated whether the tones were same or different. Thus, they were required to determine a categorical match (same or different tone), rather than an auditory match. All listeners had significantly more difficulty discriminating between mid-rising and low-dipping tones than with other contrasts. Listeners with more musical training showed significantly greater accuracy in their discrimination. Likewise, musicians’ spoken imitations of Mandarin tones (model tokens presented by a native speaker) were rated as significantly more native-like than those of nonmusicians. These findings suggest that musicians may have abilities or training that facilitate their perception and production of Mandarin tones. However, further research is needed to determine whether this advantage transfers to language learning situations.
Temporal and spectral cues in Mandarin tone recognition
Authors: Kong Ying-Yee , Zeng Fan-Gang
Published: September 2013

Temporal cues contribute significantly to Mandarin tone recognition, but the relevance of formant frequencies is debatable. This study investigates the relative contribution of temporal and formant cues to tone recognition. Three sets of Mandarin stimuli were created. Recorded whispered speech was used to test the contribution of the formant cue, 1- and 8-band noise-modulated speech with 50-Hz envelope cutoff frequency was used to test the contribution of the temporal envelope cue, and 1- and 8-band speech with 500-Hz cutoff frequency was used to test the contribution of the periodicity cue. Four normal-hearing native Mandarin speakers participated. In quiet, subjects achieved an average 87% (8-band) and 82% (1-band) correct with the periodicity cue (500-Hz cutoff), but only 72% (8-band) and 55% (1-band) correct without the periodicity cue (50-Hz cutoff). Whispered speech produced an average 72% correct. From 10 to 10-dB signal-to-noise ratios, this pattern of results was largely preserved, with whispered speech and 8-band conditions without the periodicity cue showing similar performances, which was significantly better than the 1-band without the periodicity cue, but poorer than the 8-band with the periodicity cue. These results suggest all three cues contribute to Mandarin tone recognition, and there is a trade-off among these cues.
Acoustic Mine Imaging (AMI) project: An underwater acoustic camera for use in mine warfare
Authors: Ellis Colin , Murphy Ed
Published: September 2013

This paper is submitted to detail the advances in sonar and imaging techniques and synthetic apertures being made in Australia by Thales Underwater Systems within a Australian Defence Acquisition Project termed Acoustic Mine Imaging (AMI). This paper will detail the development of the AMI underwater acoustic camera for the detection, classification and characterization of mines and other underwater objects in turbid water where optical imaging is ineffective. It will explain the history of the development from a DSTO concept to the current system. It will detail how the acoustic camera provides real-time milimetric resolution three-dimensional images and how the design has had to meet practical operational constraints to allow seamless mounting onto a small, remotely controlled underwater vehicle for mine disposal operations. An overview of the processing architecture and technical complexity of the AMI will be provided, including detail on the design and development of the required submilimeter transducers and 2D matrix array. The paper will reflect on the technical and operational challenges that had to be addressed. Finally, trial results will be presented that will demonstrate the real-time capability of the acoustic camera in various environments.
Bathymetry and seafloor acoustic backscatter imagery with a volume search sonar
Authors: Brogan Daniel S. , de Moustier Christian P.
Published: September 2013

Volume search sonars designed for mine hunting applications could be used for environmental sensing, particularly seafloor relief and texture. This capability is explored with a system that transmits a stepped FM pulse over a 243 deg vertical fan beam centered on nadir. It receives with 27 pairs of beams, symmetrically steered about nadir in the fore-aft direction and spaced at 7.16-deg intervals across track. The receive beam pair geometry allows simultaneous views of the seafloor in forward, vertical, and aft profiles. Pulse compression, monopulse processing techniques, and temporal and spatial filtering are used to estimate bathymetry and seafloor acoustic backscatter imagery of a sandy bottom and a muddy bottom. Three monopulse techniques have been investigated: conjugate product, difference over sum, and reduced beamwidth which is the most promising for this application. Results are presented for data collected while surveying at roughly 25 knots, showing the combined effects of acoustic geometry and survey speed on the resolution of the bathymetry and acoustic backscatter imagery and on bottom coverage. [Work supported by NRL Grant No. N00173-00-1-G912.]
Fourier and wavelet domain denoising of active sonar echoes
Authors: Cable Peter G. , Shah Sheila , Butler Gary
Published: September 2013

Active sonar classification performance improves significantly when echo-to-background ratios increase above 10–15 dB. To achieve the improved echo waveform fidelity implied by increasing echo-to-background, preclassification processing methods are sought to improve echo waveform estimates. For this purpose a class of nonlinear techniques termed denoising, applied to efficient Hilbert space representations of transient signals, has been shown to yield nearly optimal estimation procedures for noise corrupted signals of unknown smoothness [D. L. Donoho and I. M. Johnstone, Biometrika 81 (1994)]. We have applied several versions of Fourier and wavelet domain denoising to noisy low-frequency target echoes and, for echoes near detection threshold, have demonstrated signal representation improvements equivalent to increases in echo-to-background of 4 dB. The theoretical foundations of denoising, including a new threshold algorithm, will be outlined and measures of performance for waveform estimation will be reviewed and discussed. The experimental methodology used and the results obtained for the test sonar echoes will be summarized and target classification implications of the results obtained from the analysis discussed. [Work supported by ONR.]
Acoustic field propagation through a time-evolving buoyant jet
Authors: Finette Steven , Oba Roger , Gallacher Patrick , Piacsek Steve
Published: September 2013

Previous theoretical work regarding internal wave/acoustic wave interaction has shown that in the case of soliton (i.e., nonoverturning) propagation, significant effects on acoustic propagation occur via both amplitude and phase components. Acoustic flow visualization data obtained recently in the South China Sea [Orr and Mignerey, J. Geophys. Res. 108 (2003)] indicate the presence of internal bores with associated Kelvin–Helmholtz instabilities at the base of the mixed layer. These overturning bores are examples of nonhydrostatic dynamics associated with significant vertical acceleration of the fluid. In order to explore the effect of overturning on acoustic field propagation, we have used a nonhydrostatic hydrodynamic model to simulate the temporal evolution of internal bores. The initial condition is a stationary front separating two regions characterized by slightly different but homogeneous densities. The front is released at t=0 and the gravity-induced flow evolves into an internal bore with associated Kelvin–Helmholtz instabilities, or rotors, behind the leading edge of the bore. Results for transmission loss and signal gain degradation over a frequency range of 200–500 Hz will be presented. [Research sponsored by ONR.]
Numerical investigation of rough surface scattering in a fetch-limited environment using a parabolic equation model
Authors: Ead Richard , Smith Kevin B. , Badiey Mohsen
Published: September 2013

When compared to the open ocean, the littoral environment is responsible for a greater dispersion of acoustic energy per volume due to scattering from the sea surface, sea floor, topographic features, and disharmonious regions within the volume. Of particular interest is the modeling of acoustic energy as it is reflected and dispersed by a rough sea surface based on an empirical fetch-limited ocean wave spectrum, and how such modeling compares with measured data. Following the method of Tappert and Nghiem-Phu [J. Acoust. Soc. Am. Suppl. 1 77(2), S101 (1985)], a formulation for scattering from a rough surface has been developed that includes results from analysis of data [Hasselmann et al., JPO 10, 1264–1280 (1980)] collected during the Joint North Sea Wave Observation Project. The formulation is integrated into the Monterey–Miami Parabolic Equation Model [Smith, J. Comput. Acoust. 9, 243–285 (2001)]. The model is validated by comparing to a unique set of experimental data collected in a fetch-limited region. Arrival time and arrival-angle fluctuations are examined and compared with field data.
Alternative acoustic environments for the generation of reverberation
Authors: Case Alexander U.
Published: September 2013

The musicians and engineers who create popular recorded music view reverberation as a signal processing effect to be added to any and all elements of a multitrack production. Devices such as digital reverbs, spring reverbs, and plate reverbs are tools of the recording trade, synthesizing reverblike sounds for performance through loudspeakers. Acoustic reverberation makes its way into recorded music through the use of a reverb chamber. A small room is used to generate reverb. With cubic volume well below that of a performance hall, it works the ‘‘other side’’ of the Sabine equation, being built of highly sound reflective materials. A purpose-built room for the generation of reverb is a luxury not many studios can afford. Clever use of stairwells, bathrooms, and basements is easier on the recording studios balance sheet. This work evaluates the repurposing of these alternative spaces for the generation of reverb in popular recorded music.
Open secrets
Authors: Holzman Malcolm , Beglarian Eve , Bahn Curtis
Published: September 2013

In 1998, the Schools of Architecture and Humanities at the Rensselaer Polytechnic Institute initiated a collaborative project between students of both schools to develop a musical performance piece that would be presented in an environment to be designed and built in the Art Gallery of the School of Architecture. Students from both Schools were to work together on developing the content and conceptualizing the built environment. Architects Malcolm Holzman and Nestor Bottino of the firm of HHPA were brought in as advisors to the project, as was Composer Eve Beglarian of Twisted Tutu. Curtis Bahn, Director of the iEAR Studio at RPI, was Academic Coordinator for the project, together with Beth Weinstein, Professor, School of Architecture, and Grethe Holby, who directed the performance. This paper will review the academic raison d’etre for organizing such a program, discuss the history of the project as it developed, and present a video tape of portions of the finished performance.
Eavesdropping on elephants
Authors: Payne Katy
Published: September 2013

The Elephant Listening Project is creating an acoustic monitoring program for African forest elephants, an endangered species that lives in dense forests where visual censusing is impossible. In 2002, a 21/2-month continuous recording was made on an array of autonomous recording units (ARUs) surrounding a forest clearing in the Central African Republic. Each day between 10 and 160 forest elephants (Loxodonta cyclotis), the subjects of Andrea Turkalo’s 13-year demographic study, were present on the clearing. Thousands of vocalizations were recorded, most of which contained infrasonic energy. The calls were located in space using software developed in the Bioacoustics Research Program. During daylight hours simultaneous video recordings were made. GPS time-synchronization of video cameras and the ARUs made it possible to identify the elephants responsible for many calls and to examine associated circumstances and behaviors. Recordings were also made on a second acoustic array, permitting a preliminary estimate of propagation and an indication of source level for selected elephant calls. Automatic detection of elephant calls is increasing the feasibility of analyzing long acoustic recordings, and paving the way for finer-tuned analyses, with an ultimate goal of describing forest elephants’ acoustic repertoire.
Elephant low-frequency vocalizations propagate in the ground and seismic playbacks of these vocalizations are detectable by wild African elephants (Loxodonta africana)
Authors: O’Connell-Rodwell Caitlin E. , Wood Jason D. , Gunther Roland , Klemperer Simon , Rodwell Timothy C. , Puria Sunil , Sapolsky Robert , Kinzley Colleen , Arnason Byron T. , Hart Lynette A.
Published: September 2013

Seismic correlates of low-frequency vocalizations in African and Asian elephants propagate in the ground at different velocities, with the potential of traveling farther than their airborne counterparts. A semblance technique applied to linear moveouts on narrow-bandpass-filtered data, coupled with forward modeling, demonstrates that the complex waves observed are the interference of an air wave and a Rayleigh wave traveling at the appropriate velocities. The Rayleigh wave appears to be generated at or close to the elephant, either by coupling through the elephant’s body or through the air near the body to the ground. Low-frequency elephant vocalizations were reproduced seismically and played back to both a captive elephant and to elephant breeding herds in the wild, monitoring the elephants’ behavioral responses, spacing between herd members and time spent at the water hole as an index of heightened vigilance. Breeding herds detected and responded appropriately to seismically transmitted elephant warning calls. The captive studies promise to elucidate a vibrotactile threshold of sensitivity for the elephant foot. Elephants may benefit from the exploitation of seismic cues as an additional communication modality, thus expanding their signaling repertoire and extending their range of potential communication and eavesdropping beyond that possible with airborne sound.
Low-frequency sounds and amphibious communication in Hippopotamus amphibious
Authors: Barklow William E.
Published: September 2013

Hippos make sounds in both air and underwater, and, with their heads in an amphibious position (eyes and nostrils above water but mouth and throat below), are able to transmit sounds to both media simultaneously. Hippos on the surface respond to the surface component by calling. Hippos underwater consistently surface and call in a chorus that can spread in air from one territory to the next for many kilometers. They produce several low-frequency, high-amplitude (100 dB re: 20 μPa) sounds. The grunt, their most common call, has a 30- to 60-Hz fundamental, and the huff and some tonal sounds end with an abrupt drop in frequency to 20- to 30-Hz. These sounds are usually given amphibiously, but the high-pass filter characteristics of shallow water attenuates the low frequencies of the underwater component. Hippos also emit these and other sounds when they are completely submerged. These are inaudible in air, but they produce a fountain on the surface accompanied by a 10- to 20-Hz sound. They also produce this effect with plosive blows underwater without other sounds. Similar ‘‘bubble blasts’’ have been reported in gray whales. The function of these sounds is not clear, but they may facilitate long-distance ‘‘chain chorusing.’’
Spectrogram analysis of low to mid frequency marine mammal clicks
Authors: Ioup George E. , Ioup Juliette W. , Larue James P. , Sidorovskaia Natalia A. , Kuczaj Stan A. , Rayborn Grayson H. , Walker Christopher D.
Published: September 2013

Previous investigators have proposed explanations for some sperm whale click structure and pointed out that the separation of individual pulses within the click might be used to determine approximately the size of the sperm whales. Recently, Mohl et al. [J. Acoust. Soc. Am. 114, 1124–1154 (2003)] have shown that echo-location click structure is highly dependent on the received angle. In data measured by the Littoral Acoustic Demonstration Center using bottom-moored hydrophones in the northern Gulf of Mexico in the summers of 2001 and 2002, rich click structures were observed in the spectrograms of many click trains, some of which exhibit strikingly consistent spectral nulls across the train. Although this structure in the spectra could be due to propagation effects, investigations to date suggest this possibility is highly unlikely, as discussed in the next abstract. Therefore it is at least plausible that the structure could be used to identify individual animals. This is known to be a difficult problem in the case of sperm whales because of the angle dependence of at least some of their clicks. These difficulties are discussed, as is the possible use of the spectrograms of the clicks to identify individuals. [Research supported by ONR.]
Sperm whale identification using self-organizing maps
Authors: Ioup Juliette W. , Ioup George E.
Published: September 2013

Self-organizing maps (SOMs) are a neural network technique for clustering data with similar features. Sperm whale phonations are among the many sounds that can be heard in the Littoral Acoustic Demonstration Center underwater acoustic data from three bottom-mounted hydrophones in the northern Gulf of Mexico during the summer of 2001. When more than one whale is present, it would be useful to associate particular clicks or click trains with specific whales. SOMs are employed using various features including the time series itself, Fourier transform coefficients, and wavelet transform coefficients. Preliminary results with a relatively small data set will be presented. [Research supported by ONR.]
Multifrequency acoustic observations of zooplankton in Knight Inlet, B.C
Authors: Trevorrow Mark V. , Mackas David L. , Benfield Mark C.
Published: September 2013

A collaborative investigation of midwater zooplankton aggregations in a coastal fjord was conducted in November 2002. Midwater aggregations of zooplankton in a coastal fjord were sampled and mapped using a calibrated, three-frequency (38, 120, and 200 kHz) vessel-based echo-sounder system, a multinet towed zooplankton net (BIONESS), and a high-resolution in situ camera system (ZOOVIS). Dense daytime layers of euphausiids and amphipods near 70- to 90-m depth were found in the lower reaches of the inlet, especially concentrated by tidal flows around a sill which rises above the layer. Quantitative euphausiid and amphipod backscattering measurements, combined with in situ species, size, and abundance estimates, were found to agree closely with recent size- and orientation-averaged fluid–cylinder scattering models produced by Stanton et al. Also, in situ scattering measurements of physonect siphonophores were found to have a much stronger low-frequency (38 kHz) scattering strength, in agreement with a simple bubble scattering model. [Work supported by Dr. J. Eckman, ONR code 322BC.]
Abundance and diel migration of demersal plankton on a tropical coral reef: An acoustic pilot study
Authors: Ortner Peter B. , Stamates S. Jack , Cummings Shailer R. , Smith Sharon L. , Lane Peter V.
Published: September 2013

Coral reefs serve as the habitat for demersal mesozooplankton and small fishes that migrate into overlying waters at night but spend daylight hours within the reef in part because that habitat provides protection against visual predators. These movements structure energy, mass, and nutrient exchange between the reef habitat and the surrounding waters. Information to date has, however, been predominately qualitative and has not taken advantage of recent advances in biological oceanographic sampling instrumentation. Moreover, what sampling has been done has not been rigorously coupled to synoptic time series of ambient oceanographic conditions. To begin to fill this critical gap we deployed for two 1-month-periods multi-frequency acoustic (TAPS) and optical integrated environmental sensor packages to continuously measure and record the abundance and size distribution of organisms while concomitantly measuring water column chlorophyll, fluorescence, transmittance, temperature, and salinity. During the two periods of high-resolution sampling, and in the intervening six months, we also deployed bottom-mounted ADCP units yielding both vertical current structure and backscatter amplitude distributions. Both video footage and traditional net or pump samples were obtained for ground-truth purposes. [Support provided by the National Marine Fisheries Service/Southeast Fisheries Science Center.]