bluuebunny/crossref_metadata_2025 huggingface dataset:
Pinniped hearing and anthropogenic noise
Authors: Southall Brandon L. , Schusterman Ronald J. , Kastak David , Reichmuth Kastak Colleen , Holt Marla M.
Published: October 2013

Our behavioral studies of pinniped auditory processing, including amphibious hearing, auditory masking, and temporary threshold shift (TTS), have provided comparative data on hearing and the potential effects of anthropogenic noise for three pinniped species. Differences for one harbor seal between aerial thresholds measured using headphones in a noisy environment and those measured without headphones in a hemi-anechoic chamber are quite large. While additional data are required, the preliminary data suggest that it will be necessary to re-evaluate pinniped aerial hearing capabilities and their susceptibility to aerial anthropogenic noise impacts. Assessments of simultaneous (masking) and residual (TTS) effects of controlled noise exposure have also provided insight into the potential effects of anthopogenic noise on free-ranging pinnipeds. Our underwater masking studies indicated relatively low critical ratios for low-frequency tonal sounds, while underwater TTS studies demonstrated that auditory fatigue occurs in pinnipeds, even following exposure to moderate levels of noise. The TTS studies have also provided some means of estimating the onset of TTS and supplied data on the relative importance of fatiguing noise exposure level and duration. Results suggest that equal-energy relationships and the octave effect previously shown in humans and some terrestrial mammals may not apply for some pinnipeds.
A general-purpose acoustic recording tag for marine wildlife
Authors: Burgess William C.
Published: October 2013

Acoustic recording tags have demonstrated the potential to measure free-ranging marine animals’ exposure and response to sound. To fully realize this potential, however, acoustic recording tags must be applied to a large sample of subjects. To enable the broad use of acoustic recording tag technology, a new general-purpose tag has been developed. Miniaturization to a cylinder 3 cm in diameter by 23 cm in length allows the application with a variety of species and attachment methods. Encapsulation in resin and the use of infrared rather than electrical connectors provides durability and flexibility. The prototypes sample acoustics with 16-bit resolution at bandwidths up to 14 kHz, as well as temperature and depth with 12-bit resolution. Constant acoustic sampling at 2 kHz fills the 288-MB solid-state flash disk in 21 h, but this lifetime can be extended by reducing resolution or by recording only during times of interest. Low-power 3-V electronics allow a single half-AA-cell lithium battery to power the entire tag. The tags were deployed as seafloor recorders off Maui in March 2001, and initial deployments on free-ranging marine mammals and sea turtles are expected by fall 2001. [Work supported by ONR.]
Ship strike acoustics: It is all just shadows and mirrors
Authors: Blue Joseph E. , Gerstein Edmund R. , Forsythe Steve E.
Published: October 2013

Whales are vulnerable to collisions when near the surface and in shallow water. Here the physics of near-surface sound propagation may play a crucial role in their survival. Ships sufficient in size to mortally injury whales generate acoustic spectra dominated by very low frequencies. Since the ocean’s pressure-release surface severely attenuates frequencies that are generated at distances less than a wavelength from the surface, whales may not detect low-frequency sounds generated by approaching ships. The Lloyd Mirror Effect predicts sound pressure levels at the surface approximate zero and empirical acoustic measurements support the prediction, while quantifying another important phenomenon associated with large ships, Acoustical Shadowing. The confluence of these acoustic propagation effects pose significant ecological consequences for marine mammals at the surface. While aerial and shipboard monitoring networks help navigate ships away from whales sighted on the surface, these programs are not reliable during conditions of poor visibility and darkness. Further understanding the acoustics of whale/ship collisions could augment protection efforts and result in more consistent and effective management strategies. To mitigate collision risks at times when surveillance programs are ineffective, ships could be projecting directional acoustic signals specifically designed to defeat the Lloyd Mirror Effect and Acoustical Shadowing.
Coastal seabed tomography by inversion of drifting acoustic buoys data
Authors: Hermand Jean-Pierre , Absil Frans G. J.
Published: October 2013

A buoy field, specifically designed for shallow-water acoustic tomography, was deployed in a complex coastal environment on the western Sicilian shelf (enverse 97, Saclant Undersea Research Centre). Eight buoys drifted away from a fixed sound source receiving its repeated, broadband transmissions on their single hydrophone at fixed depths and known positions (DGPS). The 1-day run sampled, over kilometers, the acoustic impulse response (the Green’s function) of the environment as a function of range and azimuth from the source. In this paper, the mapping of sediment properties and bottom types from the ‘‘synthetic horizontal aperture’’ measurements is investigated. Statistical analyses of the frequency-dependent, mode interference patterns associated with the buoy tracks allow to isolate range-azimuth sectors of limited acoustic variability and to define regions of similar bottom conditions. Average geoacoustic parameters of these regions are determined by maximizing the processing gain of a model-based matched filter receiver [J.-P. Hermand, IEEE J. Oceanic Eng. 24, 41–66 (1999)]. The preliminary inversion results, including P-wave speed and thickness of the sediment cover, are congruent with the ground truth of a dense grid of seismic reflection profiles and sediment cores (enverse 98). [Work supported by the Royal Netherlands Navy.]
Suction cup effect coupling shear waves across unconsolidated smooth wet solids
Authors: Chamuel Jacques R.
Published: October 2013

Accurate modeling of the propagation of sound waves in unconsolidated marine sediments depends on understanding the interparticle contacts and coupling mechanisms of compressional and shear waves. The theory of elastic waves in unconsolidated marine sediments [M. J. Buckingham, J. Acoust. Soc. Am. 103, 288–299 (1998)] depends on the grain roughness, where the shear speed goes to zero as the losses vanish. The current paper examines shear wave coupling phenomena between unconsolidated solids in the absence of roughness. Fundamental experimental results are presented, demonstrating the transmission of shear waves across smooth glass plates coupled with a localized capillary thin water film hermetically sealed between the plates with the suction cup effect. The glass plates were pressed against each other while immersed in distilled water until they became slip resistant. The diffraction pattern of Newton fringes was observed surrounding the water film. Results from experiments using seawater, microbubbles, and curved surfaces are discussed leading to acoustic characterization of saturated and partially saturated marine sediments. [Work supported by ONR.]
Direct observation of the angle of intromission in marine sediments
Authors: Holland Charles
Published: October 2013

High porosity marine sediments like silty clays have the curious property that the speed of sound through its bulk medium is lower than that of the interstitial pore fluid. When a high porosity sediment is at the water sediment interface, classical theory predicts that there is an angle at which the reflection coefficient is zero, and there is total transmission of sound into the seafloor. This angle is called the angle of intromission and has not been directly observed at the seafloor to the author’s knowledge. Data from a new measurement technique show this phenomenon with remarkable clarity. Measurements of the angle of intromission in the coastal region of Italy indicate that the properties of the surficial high porosity sediments are surprisingly constant over large areas. A simple, but robust inversion method is shown for which the sediment sound speed and density can be directly obtained.
Observations of intensity fluctuations during the summer New England shelf break Primer study
Authors: Fredricks Andrew J. , Colosi John , Lynch James F.
Published: October 2013

We present intensity fluctuation statistics of point-to-point transmission data taken during the summer shelfbreak Primer experiment. We focus on broadband 400 Hz transmissions from two bottom mounted sources on the continental slope to a vertical line array on the shelf, at distances of 60 and 42 km. The data were collected over 11 days in late July and early August of 1996. Single phone, time averaged, and time and depth average intensity statistics are examined. Both tracks showed a strong M2 tidal effect on intensity, as well as mesoscale induced variations. [Work supported by ONR.]
Observing barotropic currents and tides in the Kuroshio Extension region from long-range reciprocal acoustic transmissions
Authors: Yuan Gang , Mitsudera Humio , Fujimori H. , Nakamura T. , Yoshikawa Y. , Nakano I.
Published: October 2013

Travel times of reciprocal acoustic transmissions from a 5-transceiver acoustic tomography array over a 1000-km-scale domain in the Kuroshio Extension (KE) region during summer 1997 are used to investigate the barotropic tidal currents and range-averaged large-scale low-frequency currents as well as their relative vorticity. Inverse techniques are employed to estimate the low-frequency range-and-depth averaged (barotropic) currents every 3 or 6 h from the differential acoustic travel times. Eight major tidal constituent amplitudes and phases derived from the high-frequency acoustic travel times agree well with those found from the TOPEX/POSEIDON tidal model TPXO.5 [Egbert et al., 1994]. The results show that the range-averaged barotropic currents along the section in the KE recirculation gyre flowed westward in about 4 cm/s with an uncertainty of 0.8 mm/s; this is consistent with the result of the ADCP survey on WOCE P-14N experiment, and comparable with the surface geostrophic current velocity 5 m/s determined from the SSHA of the TOPEX/POSEIDON altimeter, indicating that barotropic currents are dominant in the Kuroshio Extension recirculation gyre. Estimated daily averaged relative vorticity over a 155000 km2 area in the KE recirculation region has a near-zero mean (1.84×10−7 s−1).
A multifrequency scintillation probing of current in a stratified ocean
Authors: Fuks Iosif , Charnotskii Mikhail , Naugolnykh Konstantin
Published: October 2013

Transverse flow of inhomogeneous fluid produces fluctuation of the acoustic signal passing through it. These fluctuations vary with the CW signal frequency change due to variation of the Fresnel zone and diffraction angles. Respectively, the fluctuations of signals at two different frequencies are coherent in a low frequency range of the spectrum and noncoherent in the high-frequency band. The frequency cutoff of the correlation function of the signal fluctuation depends upon the flow velocity at given fine structure of the flow. Measurement of the cutoff frequency allows one therefore to determine the flow velocity of the fluid. The principles of this approach in application to the probing of current in the homogeneous in average ocean were considered previously [J. Fuks, K. Naugolnykh, and M. Charnotskii, J. Acoust. Soc. Am. 109, 2730–2738 (2001)]. In a stratified ocean the sound field has a modal structure connected with the fact that rays tend to bend toward region of smaller sound speed. The features of the multifrequency method of current measurements in a stratified ocean when the fine structure of the flow is determined by the realistic spectrum of internal waves and the sound field is presented as a modal set are considered in the present paper.
Single crystal piezoelectrics for advanced acoustic transducers
Authors: Hackenberger Wesley , Rehrig Paul W. , Pan Ming-Jen , Shrout Thomas
Published: October 2013

Single crystal piezoelectric materials based on Pb(Mg1/3Nb2/3)xTi1−xO3 (PMN-PT) exhibit extraordinarily high piezoelectric properties (d33>2000 pC/N; k33>90%), which are being utilized to produce transducers with revolutionary performance enhancements in sensitivity and bandwidth. Crystals of PMN-PT are currently being produced in sizes of >2.54 cm in diameter by >7 cm in length. Examples of transducer enhancements demonstrated to date include medical ultrasound transducers with bandwidths in excess of 100%, similarly broadband Tonpilz transducer elements for forward look sonar (with the additional expectation of significantly higher source level over ceramic based transducers), and vibration and vector sensors with sensitivity levels approaching the theoretical noise floor. A number of issues need to be worked out to successfully commercialize crystals for these applications, the most important of which are reducing property variations that result from compositional gradients and increasing crystal size to reduce cost. Recent advances in crystal growth techniques are expected to help solve these problems in the coming year. Single crystal piezoelectric technology is continuing to develop with new materials that exhibit broader operating temperature ranges and larger electric field induced strains than PMN-PT. Thus single crystal piezoelectrics are expected to be as broadly applicable as ceramics.
Characterization of piezoelectric single crystals for sonar and actuator applications
Authors: Robinson Harold C. , McLaughlin Elizabeth A. , Ewart Lynn , Powers James M.
Published: October 2013

Piezoelectric single crystals show great promise for sonar and actuator applications due to their very high piezoelectric constant and electromechanical coupling factor. However, in order to accurately assess their potential, the effect of operating conditions (i.e., applied electric field, mechanical loading, and temperature) on their material properties must be determined. Furthermore, the mechanical strength of these materials in compression and tension must be known to avoid mechanical failure in transducers. A brief overview of the various methods used to characterize these crystals will be presented. In particular, material properties obtained using the NUWC Newports Stress Dependent Electromechanical Characterization System (SDECS) will be detailed. The variability of these properties under applied mechanical prestress, high electric fields, and varying temperatures shall be examined. An enhancement of the piezoelectric response with the application of prestress in certain crystals will be shown. In addition, results from compression strength testing conducted at NUWC will be presented. It shall be demonstrated that these crystals are much stronger than was assumed previously. Finally, future challenges in the measurement and analysis of these materials will be identified, including the identification of material flaws and quantification of the processes that lead to cracking in piezocrystals. [Work sponsored by DARPA.]
Characterization of the nonlinear properties of PZN–PT
Authors: Lynch Christopher S.
Published: October 2013

This presentation will focus on the electro-mechanical properties of single crystals of relaxor ferroelectric PZN–PT. The characterization work begins with measurement of the drive capability of the material as a function of preload. These measurements were made by loading specimens at constant stress levels and then cycling the electric field while monitoring the resulting strain. Results to be presented are curves for stress/strain at various electric field levels, and strain/electric field and electric displacement/electric field at various constant stress loads. A second set of experiments was performed by placing the specimens in bending. In this arrangement, the tensile and compressive stress/strain behavior are determined simultaneously. This clearly shows the effects of material nonlinearity. The final set of tests takes a close look at fatigue of the material. Small cracks are intentionally placed in specimens and then the electric field is cycled. Observation of fatigue behavior will be discussed.
Musical acoustics in the science classroom
Authors: Hansen Uwe J.
Published: October 2013

The value of hands-on laboratory centered teaching of science has led to continued workshops for elementary and secondary school teachers. Emphasis for teachers in the primary grades has been on the use of music as a tool to introduce science concepts, and for teachers at the secondary level to use computer based instrumentation to perform relatively sophisticated measurements. In a recent issue of ‘‘The Hoosier Science Teacher’’ 13 activities are discussed for use in a program which uses music to introduce science concepts [U. J. Hansen, The Hoosier Science Teacher, Volume XXVI, Number 1, 4–14 (2000)]. Increasing accessibility to sophisticated computer software enhances the ability to perform rather complex experiments at the high school level. Recent workshops at regional meetings of the AAPT have introduced these concepts to High School Physics teachers. Both the role of music in the elementary science curriculum and the enhancement of the High School Physics laboratory will be discussed with specific examples.
Descriptive acoustics of music and speech
Authors: Leishman Timothy W.
Published: October 2013

Approximately 250 nonscience undergraduate students enroll each year in a Brigham Young University physics course entitled Descriptive Acoustics of Music and Speech. This general education service course, which has been taught for more than 30 years, provides an introduction to physical concepts underlying the production and perception of music and speech. Participating students receive theoretical grounding and hands-on experience in principles of general acoustics, human hearing, architectural acoustics, sound reproduction, human voice, and musical instrument acoustics. The course was originally formulated with strong encouragement and support from the faculty of other departments who wanted to have a course that encountered their disciplines from the physical science viewpoint. Sound, as a familiar area of experience to students, allows them to view aspects of their disciplines in contrasting and complementary ways. The course has become a requirement for many nonscience students and a preferred elective for others. This paper presents an overview of techniques that have been successfully used over the years to teach acoustics to these students. It also discusses new approaches that are currently under development to enhance their learning experience.
Musical instruments as tools for teaching acoustics to engineering students
Authors: Russell Daniel A.
Published: October 2013

Kettering University offers an undergraduate minor in acoustics anchored by two lecture courses and a laboratory project course taught by physics faculty. While many of the students who take these courses are more interested in the engineering and noise control applications of acoustics, most are familiar with musical instruments and quite a few play an instrument. We have found that in several instances a discussion of the acoustics of a musical instrument can be very effective at facilitating an understanding of the fundamental concepts behind the engineering applications of acoustics our students encounter at their co-op work experiences. Examples include: the physics of guitar pickups, hose trumpets, ocarinas, low-frequency models of acoustic guitars, sound radiation from drum membrane modes, radiation from a tuning fork, musical scales and intervals, and audio demonstrations of pitch and timbre. This talk will discuss and demonstrate how several such examples are used as classroom demonstrations, homework projects, and laboratory experiments.
The role of musical acoustics in teaching engineering
Authors: Collier Robert D.
Published: October 2013

A new course, Technology of Sound, is being offered at Dartmouth College to introduce students in the liberal arts to science and engineering. The course is designed to demonstrate how the science of sound is being applied to enhance the quality of life through music making and listening. The fundamentals of acoustics are studied to understand the relationships between the vibrations and sounds of string, wind, reed, brass, and percussion instruments. Associated properties and design criteria of materials, structures, and control mechanisms including musicians are studied. Key features of the course include lecture demonstrations of individual instruments, term projects and laboratory investigations, and studies of architectural acoustics. Specific examples of student projects and the development of a web site as a teaching tool and resource will be discussed as well as student comments and evaluations. A visit to Symphony Hall in Boston is a highlight at the end of the course.
How can we preserve and promote compatible land use in the age of shrinking aircraft noise contours?
Authors: Murphy Deborah W.
Published: October 2013

Technological advances in source noise reduction combined with legislated or economics-driven changes in fleet mix composition have created the age of shrinking noise contours at many airports, even though the number of operations continues to increase. All too often, the majority of noise complaints come from residents located outside the airports Day–Night Average Sound Level (DNL) 65-dB noise contour, which is the threshold of compatibility established in the FAAs land use compatibility guidelines. If the local community feels strongly that their threshold of compatibility is less than DNL 65 dB, what can they do about it? The FAA will recognize a locally established standard and approve mitigation measures based on that standard. However, with that comes a responsibility on the part of the local jurisdictions to implement measures to prevent development of new noncompatible land uses in areas exposed to noise levels above their threshold of compatibility. This is crucial since the FAA will not approve or fund remedial mitigation of new noncompatible land uses built after October 1, 1998. This paper will explore ways the airport operator, the surrounding community, and the local jurisdictions may all be able to get what they want, with the blessing and funding of the FAA.
On the solution of inverse acoustic scattering problems using shape sensitivity analysis
Authors: Feijoo Gonzalo R. , Pinsky Peter M. , Oberai Assad A.
Published: October 2013

The solution of inverse acoustic scattering problems is considered, i.e., some measures of the pressure field in an acoustic domain are given and we are asked to identify the shape of the object that produces them. The problem is considered in an optimization framework where a cost function is introduced to quantify the error between a guess for the shape of the scatterer and the actual shape. Starting from an initial guess, the algorithm produces a sequence of shapes that converge to a local minima of the functional. At each step, the algorithm requires calculation of the cost function and its derivative with respect to changes in the shape. An efficient method for calculating shape derivatives is introduced. The method is based on the solution of an adjoint problem, which is of the same type as the acoustic scattering problem. The main characteristic of this method is that, irrespective of the number of parameters used to describe the shape of the scatterer, only one adjoint problem is solved for calculating all the derivatives. Numerical examples that demonstrate the efficacy of this approach are presented.
On the solution of three-dimensional inverse acoustic scattering problems
Authors: Farhat Charbel , Tezaur Radek , Djellouli Rabia
Published: October 2013

A computational methodology for retrieving the shape of an obstacle from the knowledge in a limited aperture of its acoustic far-field pattern is presented. This methodology, which features a reconstruction algorithm for the far-field pattern, also distinguishes itself from existing iterative Newton-type procedures by (a) the usage of exact Jacobian matrices for formulating the linearized problems rather than approximate ones (i.e., based on finite differences), (b) a fast numerical procedure for computing these Jacobian matrices, and (c) a fast and numerically scalable fictitious domain decomposition method for high-frequency acoustic scattering problems. The salient features of this computational methodology are illustrated with several submarine applications. [Work supported by ONR.]
Local/global methods for structural acoustic radiation and scattering
Authors: Bliss Donald , Franzoni Linda
Published: October 2013

Solving structural acoustic problems in the mid-frequency range is a challenging task. Computation is expensive due to the large well-coupled nature of the fluid-structure system. Discrete structural elements, e.g., ribs and stiffeners, cause localized discontinuities that require much greater resolution than would be otherwise warranted. Radiation and scattering problems having certain types of constraints exhibit great sensitivity to fine-scale convergence. Our purpose in this research is to devise analytical and numerical ways to recast such problems to be amenable to an efficient and accurate numerical solution. Analytical/Numerical Matching (ANM) decomposes a problem into local and global parts. Analysis methods extract the local discontinuities, replacing the original discrete influence of the inhomogeneity by smooth forces. A smoother computational problem can be solved efficiently, without loss of information. The method has been demonstrated for configurations of increasing complexity, and has become a useful tool for solving realistic problems. The ANM approach has been successfully applied to the modal/FEA structural-acoustics code sonax, providing a new capability to handle 3-D structural discontinuities. Future research on the application of ANM to other finite element structural-acoustic codes is outlined. An ongoing effort to develop a general theory of structural acoustic homogenization is also summarized.
Analysis of interior and exterior sound fields using iterative boundary element solvers
Authors: Ochmann Martin , Hetey Laszlo , Marburg Steffen
Published: October 2013

The boundary element method (BEM) is an efficient tool for the calculation of interior and exterior sound fields. However, the discretization of the Helmholtz integral equation often leads to large, unsymmetrical, and fully populated systems of linear equations. Such systems can be solved by means of various iterative solvers. Three examples are considered: First, a preconditioned version of the generalized minimum residual method (GMRES) is used for calculating the high-frequency acoustic scattering from cylinderlike structures. Second, the sound field in a passenger compartment is analyzed by using five different iterative solvers: GMRES, the conjugate gradient squared algorithm (CGS), the quasiminimal residual approximation (QMR), the biconjugate gradient stabilized algorithm (BICGSTAB), and the conjugate gradient iteration on the normal equations (CGNR). These methods and a Gaussian elimination are compared with respect to their numerical performance and speed of convergence. Third, scattering and radiation of a nonconvex structure is investigated. This structure—called ‘‘cat’s eye’’—consists of a sphere, where the positive octant is cut out. The efficiency and accuracy of the above mentioned five iterative methods are studied for the vibrating cat’s eye. By means of the preconditioned GMRES, scattering cat’s eyes of several thousand boundary elements can be treated on personal computers.
Speaking rates of American and New Zealand varieties of English
Authors: Robb Michael , Chen Yang , Maclagan Margaret
Published: October 2013

Measures of speaking rate provide an index of speech timing control. The present study sought to evaluate speech timing control in two varieties of English, American English (AE), and New Zealand English (NZE). Measures of speaking rate were calculated for 40 adult AE speakers which were then compared to a group of 40 adult NZE speakers. Results of the analysis identified significantly faster speaking rate and articulation rate among the NZE speakers compared to AE speakers. Vowel changes occurring in both varieties of English over the past decades, as well as contrasting rhythmic properties, are proposed to account for the rate differences. Because temporal differences can be a component of disordered speech and are a major component in certain motor speech disorders and disorders of fluency, normative speaking rate data are often utilized by speech–language pathologists. The present results, viewed from a clinical standpoint, would suggest that the particular variety of English spoken by a client is an important variable when addressing disorders of speech timing.
Toward a perception based model of the production of prosody
Authors: Dogil Grzegorz , Moebius Bernd
Published: October 2013

The speech production model proposed by Guenther, Perkell, and co-worker’s [Guenther et al., Psych. Rev. 15 (1998); Perkell et al., J. Phon. 28 (2000)] is generalized from the predominantly segmental perspective to a new theory of the production of prosody. It is posited that the only invariant targets of the production of prosodic events are perceptual targets, characterized as multidimensional regions in the perceptual space. Prosodic gestures are planned as trajectories that reach and traverse the perceptual target regions. Successfully executed gestures produce acoustic realizations of perceptually relevant prosodic events. The prosodic interpretation of the speech production model is structured around a hierarchy of prosodic domains: discourse structure, information structure, and accentual structure. It is assumed that the linguistically relevant and phonologically distinctive functions of prosodic features are represented by internal models. Once acquired, the phonemic settings pertinent to these models are stable and resistant to change, and they do not rely on continuous auditory feedback. We further suggest that the mechanisms involved in prosody control, may not differ categorically from those that control segmental speech production.
Word perception in time-compressed speech
Authors: Quené Hugo , Janse Esther
Published: October 2013

Certain applications, e.g., voicemail playback or text read-out, time-compress their output speech, usually in a linear fashion. This paper compares spoken-word perception, as measured by phoneme monitoring, in natural fast-rate speech and in normal-rate speech that is linearly time-compressed to the same fast rate. Perception is predicted to be more difficult in the natural-fast condition, in spite of its naturalness, due to its reduced articulation and intelligibility. Results show that listeners indeed reacted considerably faster in the time-compressed condition, as predicted. Nevertheless, the time-compressed condition suffers from inappropriate timing patterns, since fast-rate speech timing patterns differ from normal-rate speech on which it is based. In a second experiment, it is investigated whether perception can be improved by providing listeners with the appropriate timing patterns. To this end, the timing patterns (segmental durations) of time-compressed speech are manipulated to equal those of natural-fast speech. Hence the effects of segmental intelligibility and of temporal patterns can be separated. In summary, results obtained so far show that spoken-word perception in natural-fast speech is hampered by speakers reduced articulation. In time-compressed speech, the perceptual advantages of improved segmental intelligibility are apparently more important than the abnormality of hearing very fast but fully articulated speech. a)Hugo Quené is currently at Linguistics Department, Indiana University, Bloomington, Indiana.
Frequency and category factors in the reduction and assimilation of function words
Authors: Kanwischer Dara , Gick Bryan , Wilson Ian , Shi Rushen
Published: October 2013

It has been observed that there are phonetic and phonological differences between function words and content words. However, it is unclear whether these differences are actually the result of the distinct syntactic categories, or of other secondary effects such as frequency or stress. A production experiment was conducted to distinguish between the factors of category and frequency while controlling for stress. EPG and acoustic data were collected for five subjects. The effects of the two factors were examined within several processes of reduction and assimilation, including final-t/d dropping, initial-/h/ dropping, and palatalization. Preliminary results suggest that both word frequency and category are important factors in these processes. The consonant-dropping processes seem to show a strong sensitivity to category, but also show within-category effects of frequency. Palatalization appears to be a more gradient phonetic process, with results thus far suggesting greater sensitivity to frequency than to category. The fact that the same processes were affected by both factors suggests that at least some of the phonetic and phonological properties traditionally assigned to function words as a category may be wholly or partly the result of high word frequency. [Research supported by NSERC.]
Effects of subphonemic variation depend on lexical competitor environment
Authors: van Alphen Petra
Published: October 2013

A cross-modal identity priming experiment examined whether subphonemic variation (length of prevoicing in syllable-initial stops in Dutch) influences lexical access. Word and nonword targets began with voiced plosives. They were chosen so that half of them became words when the initial voiced plosive was replaced by its voiceless counterpart, while the other half changed into nonwords. The visual targets were preceded by auditory word or nonword primes which were either phonologically unrelated or identical to the target. The initial plosives of the identity primes had 0, 6, or 12 periods of prevoicing, but all were identified as voiced. This VOT manipulation had no effect for word targets: lexical decisions were faster after all three identity primes than after the unrelated primes. However, reaction times to nonword targets with word competitors (e.g., BRINS, with the competitor PRINS ‘‘prince’’) were slower when preceded by identity primes without prevoicing than when preceded by primes starting with 6 or 12 periods of prevoicing. This suggests that voiceless competitors are activated by words starting with voiced plosives without prevoicing. Subphonemic variation appears to influence the degree of lexical activation, but this effect depends on the lexical competitor environment.
Application of extended Kalman filtering to tracking of airborne high-speed broadband acoustic sources
Authors: Frazier William G. , Williams Chad M. , Williams Jay E. , Gilbert Kenneth E.
Published: October 2013

A technique for tracking airborne high-speed (subsonic) broadband acoustic sources is presented. This technique is based upon the familiar extended Kalman filter algorithm used in navigation, radar-based tracking, and feedback control applications. In this application, acoustic sensor-to-source bearing measurements from two locations are used to estimate target position, speed, and heading in near real time. In particular, two strategies for compensating the variable delay in obtaining bearing information caused by sound propagation are developed and presented. One of these is based upon a simple linear predictor. While adequate for sources that are not too distant from the acoustic sensors, it is shown to perform inadequately in some longer-range situations. A second approach, based upon reformulating the Kalman filter to work in conjunction with a generalized triangulation algorithm, is shown to be more robust. Advantageous features of employing a Kalman filter approach to tracking problems include the ability to systematically compensate for measurement noise and to accommodate target maneuverability constraints. Application of the technique to data obtained from a highly maneuverable low-flying commercial aircraft are presented and compared to flight path data obtained via the Global Positioning System.
Characterization of the left/right bearing ambiguities for passive line arrays
Authors: Boyle Frank A. , Grant David E.
Published: October 2013

The symmetry of a straight horizontal line array produces a left/right bearing ambiguity that makes it impossible to determine on which side of the array a source is located. A simple technique for resolving left/right ambiguities is to break the symmetry by curving the array. Under certain common conditions, however, significantly curved arrays still possess left/right ambiguities that depend on the source’s range and the beamformer’s focal length. These ambiguities can be modeled, given a source and array configuration, to produce a prediction of source localization capability. Comparisons with actual data were generally consistent with modeled results in the cases considered. The presentation will include a description of how the ambiguities are modeled, and a comparison between modeled and experimental results. Considerations on how curved arrays can be configured to minimize ambiguities will also be discussed.
Deconvolution of chirp sidescan sonar data
Authors: Ioup Juliette W. , Kalcic Maria T. , Bibee L. Dale , Kaminsky Edit J. , Ioup George E.
Published: October 2013

The first return of a sidescan sonar chirp contains information about the bottom and immediate subbottom character and roughness. Measured real data from a chirp sidescan sonar are basebanded, producing complex signals. These signals are deconvolved using an ideal transmitted source signal, a measured source signal, and, for cross-correlated data, the autocorrelation of the source. Four deconvolution techniques are used: (1) Fourier division in the frequency domain; (2) a least squares technique in the time domain; (3) the reblurring iterative deconvolution method of Kawata and Ichioka (which by definition uses the autocorrelation of the source); and (4) an alternative always-convergent modification of van Cittert iterative deconvolution. The deconvolved signals are compared to the cross-correlation of the source with the received signal (matched filter) without deconvolution. Results are discussed in relation to the known bottom characteristics. [Research supported in part by an NRL/ASEE Summer Faculty Fellowship and ONR.]
Method to enhance the low-frequency perception from a parametric array loudspeaker
Authors: Karnapi Furi Andi , Liew Yew Hin , Lee Kelvin , Gan Woon Seng
Published: October 2013

Human auditory system does not perceive the sound signal of all frequencies with equal loudness. Based on equal loudness curves, it is known that a low-frequency signal needs to be produced with a higher-power level to have the same loudness as the middle frequency part. There are two ways to overcome this problem; either boosting the power of the low-frequency part or utilizing the psychoacoustics effect called the missing fundamental. There are many works which have been done utilizing psychoacoustics to enhance the low-frequency perception of audio signal. These works are implemented to normal audio systems. Normal audio systems are comprised of a loudspeaker as the audio reproduction end. It is proposed to implement the low-frequency enhancement to a parametric array loudspeaker. The use of a parametric array loudspeaker to generate highly directional audible signal has been reported in several literatures. However, this audible signal lacks low-frequency content. One of the reasons is the relatively low-power level produced by the existing parametric array. By utilizing the nonlinearity property of the air itself, it is proposed to psychoacoustically enhance the perception of the low-frequency part.
Some shallow water reverberation highlights and bottom parameter extractions in the 80–4000 Hz region from the boundary characterization and geoclutter experiments
Authors: Preston John R. , Ellis Dale D.
Published: October 2013

Together with SACLANTCEN, the authors recently participated in two trials to measure shallow water bottom reverberation near Sicily and the STRATAFORM off New Jersey. Sources were monostatic SUS charges and coherent pulses. The receivers were horizontal arrays. Data were analyzed in bands from 80 to 4000 Hz. Highlights of the reverberant returns are discussed. The STRATAFORM is known to have benign surface morphology but contains many buried river channels. One author was also involved in the 2001 Geoclutter experiment conducted in STRATAFORM using coherent bistatic sources near 400 Hz. Differences in reverberation characteristics between SUS and Geoclutter results are discussed. Another objective of these reverberation experiments was to quickly invert for scattering and geoacoustic parameters. A simulated annealing (SA) algorithm was used together with the Generic Sonar Model (NUWC). After automatically adjusting bottom loss and scattering strength, good agreement is achieved between the diffuse reverberation data and model predictions in relatively flat areas. Model/data differences are generally correlated with bottom scattering features. Since reverberation typically lasts 10–20 s or more, extracted parameters apply over wide areas. Local bottom loss and backscattering measurements were made by Holland in these areas. A comparison with Holland’s results is given. [Work supported by ONR Code 32, Grant No. N00014-97-1-1034.]
The Geoclutter experiment: Remotely imaging sub-bottom geomorphology in shallow water
Authors: Makris Nicholas C. , Ratilal Purnima , Lai Yisan , Scheer Edward
Published: October 2013

Preliminary results of the Geoclutter experiment of April–May 2001 are presented. This bistatic reverberation experiment was conducted at the New Jersey Strataform site in continental shelf waters. Roughly 3000 waveforms were transmitted from vertical source arrays in the 390–440 Hz band and received by a horizontally towed array. On average roughly 10–100 discrete clutter events were registered per transmission for a total of at least 30000 geoclutter events that could be confused with a discrete target over the period of the experiment. Bathymetry throughout the New Jersey Strataform area is extremely benign with few discrete features. The vast majority of clutter returns appeared in level areas where absolutely no bathymetric features are present. The clutter events often registered well with buried river channel networks previously characterized in the Geoclutter program. Extensive probing of river-channel-infested areas revealed that the number and level of clutter events is highly dependent on bistatic orientation. The registrations suggest that bistatic aspects that produce ‘‘glints’’ from large projected areas along river channel axes yield the strongest and most frequent targetlike returns. These results are consistent with those predicted by a unified model for reverberation and submerged-target scattering [J. Acoust. Soc. Am. 109, 909–941 (2001)].
Use of model predictions to interpret shallow water directional reverberation data
Authors: Ellis Dale D. , Preston John R.
Published: October 2013

Most shallow water environments are variable over relatively short ranges. Low-frequency reverberation is typically dominated by bottom scattering, and therefore has considerable dependence on range and azimuth. Directional receivers, such as towed line arrays, are an important tool for measuring this azimuthal dependence. Not many reverberation models are capable of handling these beam patterns, but two which have proved useful are the Generic Sonar Model developed at NUWC and the OGOPOGO normal-mode model developed at DREA. By adjusting the bottom scattering strength and sometimes the bottom loss, good agreement has been achieved between the reverberation data and model predictions in relatively flat areas. Differences between the ‘‘flat-bottom’’ model predictions and data are generally correlated with bottom scattering features. The talk will focus on comparisons of model predictions with towed array data obtained in joint trials with the SACLANT Undersea Research Center. The comparisons can be used to extract estimates of average bottom loss and scattering parameters, and to produce crude scattering maps of the bottom. These maps of scattering anomalies, showing the differences between the measurements and the smoothed flat-bottom model predictions, indicate the challenges for range-dependent and more sophisticated models.
Predicting mono and bistatic reverberation for shallow water waveguides with detailed environmental descriptions
Authors: LePage Kevin D.
Published: October 2013

Over the past several years a suite of mono and bistatic scattering and reverberation tools have been developed at SACLANTCEN for the purpose of predicting reverberation in range dependent shallow water waveguides where high-resolution environmental information is available. Here the theoretical underpinnings of these models is described with particular attention being paid to the following issues: (1) the importance of coherent effects of propagation in reverberation; (2) the effects of range dependence of bottom properties, bathymetry, and sound speed profile on propagation and scatterer excitation; (3) the importance of the spatial scales and distributional properties of the scatterers; and (4) the significance of coherent effects in backscatter from features. Examples of predictions are compared to experimental measurements from the Malta Plateau where supporting high-resolution environmental descriptions are available.
Technical aspects of the comprehensive acoustic simulation system (CASS) reverberation model and comparisons with measured data
Authors: Weinberg Henry , Keenan Ruth
Published: October 2013

The Comprehensive Acoustic Simulation System (CASS) has recently received interim acceptance into the United States Navy’s Atmospheric and Oceanographic Master Library (OAML). This paper focuses on the application of the CASS to computing reverberation in shallow water. The first topic reviews the numerical approach. This is based on the usual assumption that reverberation received at a specific time can be found by integrating returns from ensonified scattering areas on the ocean boundaries and from ensonified volumes within the ocean proper. The same approach is used for monostatic and bistatic modes of operation. CASS contains various methods for integrating over bearing and frequency. The second topic compares computed results with torpedo data measured off the waters of southern California. This data confirms the requirement for including range-dependent effects in shallow-water reverberation modeling. Fortunately, the measured reverberation was accompanied by an excellent survey of bottom properties. Since this is typically not the case, current modeling developments in CASS include the extraction of environmental properties from measured reverberation. Future developments may reduce some of the known deficiencies.