bluuebunny/crossref_metadata_2025 huggingface dataset:
The nature and time course of the relationship between surface variability and linguistic processing.
Authors: Shah Amee , McLennan Conor
Published: October 2013

It is becoming increasingly prevalent to study and understand the role of surface information in the process of speech perception and to attempt to accommodate these variables in theories of speech perception. Indeed, theories of speech perception increasingly require an account of the precise circumstances under which surface details affect the ease with which listeners access spoken words. To date, the majority of studies have focused on manipulating various components of surface information (e.g., speaking rate, talker differences, dialect difference, and so on) to determine whether these manipulations matter to the processing task. The present set of studies in our laboratory represents the converse component of this relationship in order to determine whether linguistic complexity can affect or modulate listeners’ overt subjective impressions of the surface information. Two different methodologies, including semantic priming and repetition priming, were used manipulate ease of lexical access and determine the role on listeners perception of surface details (foreign accent). Additionally, the time course of the effect of linguistic context on accent rating judgments was studied as it manifested itself differently at different points during perceptual processing. Overall, these studies help understand the complex nature of the relationship between surface variability and linguistic processing.
Influences of auditory object formation on speech perception.
Authors: Shinn-Cunningham Barbara G. , Wang Dali
Published: October 2013

In common social settings, our ears receive a jumbled mixture of sound coming from different sources in different directions. A normal hearing listener is adept at using the low-level acoustic structure in the sound mixture to organize this cacophony into auditory objects, each corresponding to a distinct talker (i.e., performing auditory scene analysis). Typical listeners are also proficient at focusing on the talker of interest and ignoring distracting objects (i.e., directing selective attention to the desired object). Often, despite the efficacy of object formation and selective attention, portions of an attended object are inaudible, masked by sources that overlap the attended source in time and frequency. In such situations, listeners “fill in” the missing speech and extract a meaningful, whole message from the sound mixture, a process known as “phonemic restoration.” This talk will review some recent studies demonstrating that the process of phonemic restoration, which relies on high-level, acquired knowledge about speech structure and meaning, is directly impacted by low-level acoustic attributes that influence auditory grouping. These results demonstrate the inter-connected nature of the high-level processes that allow listeners to communicate in challenging settings.
Alternative signal processing models for broadband underwater propeller sounds.
Authors: Atlas Les , Clark Pascal , Kirsteins Ivars
Published: October 2013

Underwater propeller sounds often have audibly rhythmic characteristics. These sounds are commonly modeled as a broadband noise carrier multiplied by a rhythmic modulator, where analysis of the modulator wave form can provide information relating to the speed and identity of the source vessel. A natural assumption is to posit a purely periodic modulator, considering the rotary action of the propeller, which is useful for deriving maximum-likelihood estimates of the shaft rate [Lourens and du Preez, J. Ocean. Eng. 23, 4, (1998)]. Indeed, recorded propeller data are unmistakably rhythmic, but the assumption of a strictly periodic or cyclical modulator wave form is questionable. A critical analysis of the periodicity assumption is presented and compared to three alternatives. Maintaining the product form in which the modulator wave form multiplies a random broadband carrier, the possible modulator signals are generalized to include: (1) almost-periodic functions expressible by nonharmonic trigonometric series; (2) multiplicative cascades of possibly complex-valued modulator functions; and (3) stochastic processes in which random state transitions constitute a sense of repeatability or rhythm. In this work, three modulator models are contrasted as estimators of periodicity, using actual propeller sound recordings to validate these estimates. [This work is supported by the Office of Naval Research.]
The propagation of noise in a dispersive medium.
Authors: Cohen Leon
Published: October 2013

If noise is generated at a particular region, it will generally propagate and be nonstationary in position and time. We present a phase space approach to understand the propagation of noise in a dispersive medium and to present methods to ascertain when the noise is stationary or quasi-stationary. The damping case is also discussed. In addition, we present approximate methods that allow one to study the statistical properties of the evolution of the noise field in space and time in a relatively simple way. A number of examples will be presented. [Work supported by ONR.]
Classification of shallow water passive sonar signals using stochastic channel model.
Authors: Gupta Maya , Anderson Hyrum , Mortensen William
Published: October 2013

This paper addresses the problem of classifying passive sonar signals propagating in shallow water channels. A key problem is that such signals are corrupted by noise and multipath, which we model stochastically in terms of the expected multipath and noise, and the variance of the multipath and noise. We assume that free-field (e.g., deep water) training signals are available. We show that for classification, the accuracy can be improved by not committing to an estimate of the channel or signal, but rather by marginalizing out the channel and noise uncertainty. Specifically, we propose variants of the quadratic discriminant analysis (QDA) classifier and the support vector machine classifier (SVM) that probabilistically account for the unknown channel effects, and which avoid ill-posed deconvolution. The proposed classifiers can work either directly on a time signal or on subband power features. Results on simulated data and real Bowhead whale vocalizations show that we can significantly improve classification performance over traditional methods over a range of signal-to-noise ratios. In addition, we will discuss the case where the classification decision can be made by multiple cooperating receivers, such as in a sonar network.
Kirchhoff scattering from underwater targets modeled as an assembly of triangular facets.
Authors: Abawi Ahmad T.
Published: October 2013

Scattering from underwater targets is a challenging problem, mainly because many of the techniques developed in scattering theory are for radar applications and, therefore, appropriate only in free space. Underwater scattering occurs in a waveguide, which in most cases requires a modification if not a reformulation of the methods developed for scattering from targets in free space. The most accurate solution of scattering from a target in a waveguide can be obtained by solving the wave equation in an environment that contains the waveguide and the target and simultaneously imposing boundary conditions on the boundaries of the waveguide and on the surface of the target. However, this technique is numerically intensive making it impractical in most cases of interest. As a means of offering a more practical solution, we show how to solve the scattering problem from a target in a waveguide by (1) modeling it as an assembly of triangular facets, (2) computing scattering from each facet analytically using the Kirchhoff approximation for each set of incident and scattered plane waves, and (3) combining the solutions coherently. We compare this solution with those obtained using more accurate methods such as the virtual source technique.
Bistatic synthetic aperture sonar and acoustic holographic imaging of a tilted circular elastic plate.
Authors: Tuazon Neil , Marston Philip L.
Published: October 2013

Circular plates have axial symmetry and are sometimes used as components of items relevant to applications of sonar to detection and classification. Measurements of the backscattering spectrum as a function of tilt angle for an isolated circular plate reveal bright features associated with the excitation of compressional and flexural waves on the plate. Some of the features were previously found relevant to the interpretation of acoustic holographic images based on 2-D hydrophone scans close to a circular plate [B. T. Hefner and P. L. Marston, ARLO 2(1), 55–60 (2001)]. In the present research, bistatic synthetic aperture sonar (SAS) and holographic images were constructed from line scans of a hydrophone at a large distance from the plate using a method previously summarized [K. Baik, C. Dudley, and P. L. Marston, J. Acoust. Soc. Am. 121, 3203 (2007)]. Because of elastic responses, the images are bright even when the receiver scan line does not intersect specular reflections from the plate. The radiation by the transient elastic waves excited on the plate can significantly increase the contrast of SAS and holographic images. [Work supported by ONR.]
Modelled Doppler and range resolutions of active pulses in simulated environments.
Authors: Holden Andrew
Published: October 2013

The ability of an active sonar waveform to simultaneously estimate the range and velocity resolution of a target can be predicted by the wideband ambiguity function. Although this gives good insight into the capabilities of different pulse types, it does not replicate a real active sonar where a transmitted pulse is propagated through an environment and the received pulse is cross-correlated with a number of frequency and time shifted replicas of the transmitted pulse. In order to predict this a ray trace model is used to calculate the travel time and received amplitude of each ray path from the transmitting sonar to a target and back to include seabed and sea surface scattering where complex broadband pulse types can be modelled using a sub-band approach. This allows the determination of Doppler and range resolution for a variety of pulse types including pulse trains of LFM pulses in simulated environments, especially highly reverberate shallow water environments.
Coupled ocean-acoustics studies at Navy and NATO laboratories: The legacy of Ralph Goodman.
Authors: Piacsek Steve A. , Barron Charlie N. , Porter Michael
Published: October 2013

A brief history of collaborations between ocean and acoustic modelers is given under the directorships of Ralph Goodman at NORDA and SACLANT, and of continuing coupled modeling studies at NRL built on previous studies he sponsored. At NORDA the Numerical Modeling Division consisted of an acoustic and an ocean branch, one of the first known instances of such close-knit administrative units for ocean and acoustic modelers. At SACLANT, close collaborations were strongly encouraged by Ralph Goodman and the respective group leaders. The results of these studies eventually appeared among the first published papers on the effects of mixed layer and Gulf Stream properties on surface-duct propagation (Computational Acoustics: Ocean-Acoustic Models and Supercomputing (North Holland Press, 1990); Oceanography and Acoustics: Prediction and Propagation Models (AIP Press, 1994). At NRL, these studies were restarted recently: evaluation of sonic layer depth relative to mixed layer depth [JGR 113 (2008)]; the acoustic impact on marine mammals [AGU Ocean Sciences Meeting (2006)]; and the acoustic impact of propagating internal solitons [IEEE Journal of Ocean Engineering (2007)]. Examples will be given from some of these studies to show progress in the field.
Ralph Goodman and Hamiltonian acoustics.
Authors: Kuperman W. A.
Published: October 2013

Much of the underwater acoustic community that has worked with ray theory starts from the eikonal-ray equations. Since these equations, which are solved numerically, can be derived from a high-frequency asymptotic expansion, Fermat’s/Hamilton’s principle is typically bypassed. Historically, the introduction of the Hamiltonian formulation of underwater acoustics ray has come from scientists with a background in classical physics and/or from researchers whose goals were to study complicated environments, chaos, etc., using the well developed formalism of Hamilton’s equations and perturbation theory. Mostly, these latter applications go back to the 1980s. Among Ralph Goodman’s earliest work in underwater acoustics is a paper [R. Goodman and R. B. Duykers, J. Acoust. Soc. Am. 34, 960–962 (1961)] in which he derived the Hamiltonian for convergence zone rays in the harmonic oscillator approximation and then solved the equations by inspection. This paper must be one of the earliest applications of the Hamiltonian formulation to underwater ray acoustics and a part of the beginning of an illustrious career in the underwater acoustics community.
Extending bubble measuremenets below 20 μm: in memory of Ralph Goodman’s contributions.
Authors: Czerski Helen , Farmer David
Published: October 2013

No matter which aspect of underwater acoustics we worked on, conversations with Ralph Goodman invariably added insight and often motivated new lines of investigation. This was certainly true of our interest in measuring bubble size distributions. We discuss the extension of acoustical measurement of bubbles to radii below 20 μm, a topic of particular relevance to the study of optical scatter in the ocean. Extending the frequency range of a resonator to 1 Mhz would in principle allow measurement down to ∼3 μm, but significant challenges arise due to the confounding effects of geometric scatter from larger bubbles. This problem becomes greater for measurements of smaller bubbles, requiring a careful analysis of the accuracy limits imposed on the inversion procedure. Preliminary steps along this path are discussed with examples drawn from recent field measurements.
Anomalous dispersion and pulse propagation in oceanic bubble clouds.
Authors: Henyey Frank S.
Published: October 2013

During a planning meeting for the Scripps pier bubble experiment, Ralph Goodman suggested we apply the Kramers-Kronig relations to bubble cloud data. By “we,” I assumed he meant that I should do it. I applied the Kramers-Kronig relations to David Farmer’s Scripps pier data from his modified Medwin resonators. This allowed a determination on which data had lower accuracy than the rest. Using the high accuracy data, I constructed a model of the complex sound speed. No formula relating bubble size distributions was needed. This model has anomalous dispersion in a frequency band that nearly coincides with a region in which the group speed is higher than the sound speed in bubble-free water. Summerfeld’s theorem prohibits any signal from traveling that fast. The consequences for pulse propagation within bubble clouds was determined, using pulses having the same frequency spectrum as transmitted by Jerry Caruthers. The predicted nature of the received pulse is only partially described by Brillouin’s studies, done before computers existed.
Conversations with Ralph about bubbles in the surf zone.
Authors: Deane Grant B.
Published: October 2013

Ralph Goodman made many contributions to the field of oceanic bubbles. This talk will focus on conversations with Ralph about bubbles in the surf zone. Questions that Ralph asked about surf zone bubbles included: where are they, and what are their acoustical properties? These fundamental questions will be examined in the light of Ralph’s own experimental and theoretical work, with some contributions from the author. [Work supported by the Office of Naval Research.]
Ralph Goodman’s recent contributions on oceanic bubbles.
Authors: Caruthers Jerald W. , Stanic Steve
Published: October 2013

Many of us are never too old to have an esteemed mentor such as Ralph Goodman. We have for the past decade and a half had the pleasure and privilege of conducting research on oceanic bubbles with his help and advice. Over this period, bubble research has been his main focus. It is appropriate that we highlight his leadership and contributions with us on oceanic bubbles. This presentation will provide snapshots of a number of publications and presentations on bubbles since 1993. [Work supported by ONR and NRL.]
Attenuation measurements across surface-ship wakes and computed bubble distributions and void fractions: A tribute to the contributions by Ralph Goodman on oceanic bubbles.
Authors: Stanic Steve , Caruthers Jerald , Goodman (Deceased) Ralph , Kennedy Edgar , Brown Bob
Published: October 2013

A series of three CW-pulsed signals were transmitted across a surface ship wake as the wake aged. Each transmission contained a set of four 0.5-ms-long pulses that ranged over frequencies from 30 to 140 kHz in 10-kHz steps. The acoustic attenuation across wakes that were due to varying bubble-size densities within the wakes were determined experimentally. From those data, estimates of the bubble densities as functions of the speed of the wake-generating ship, the wake’s age, and acoustic frequency were calculated. From the bubble-density results, power-law fits and void fractions are calculated. The attenuation measurements were taken at 7.5-m intervals behind the wake-generating ship and continued for about 2 km. The experiment was run for wakes generated at ship speeds of 12 and 15 knot wakes. The bubble densities were observed to have power-law forms with varying parameters with the strongest, for early ages, having an exponent of −3.6 and a void fraction of 4×10−7, and with both diminishing for older wakes, as might be expected. This work was Ralph Goodman’s last contribution in underwater acoustics. [Work supported by the Naval Research Laboratory Program Element 62435N and the Office of Naval Research Code 321OA.]
A suggested method to be used to measure the scattering coefficient of full-scale samples.
Authors: Sauro Ron
Published: October 2013

In attempting to follow ISO 17497-1 as a method for measuring full-scale scattering coefficients, it was observed that many of the recommended steps needed to be modified for those full-scale measurements. Variations were tried to aid in these measurements. These variations are described and suggested solutions to the problems observed are presented. It was observed that continuous rotation of the sample, rather than step action rotation, worked better for taking consistent data from the sample. A stable chamber environment is also necessary with humidity reaching at least 50% and temperature variations should not vary by more than 1°C throughout all four parts of the test. It was also observed that a less directional source than recommended was needed so two dodecahedron loudspeakers were chosen to reproduce a combined weighted noise stimulus source. Six data microphones were placed at random locations and varying heights to collect data. Data were compared between the suggested method and the ISO-17497-1 standard.
Prediction and tailoring of steady-state broadband sound fields in enclosures using absorption scaling and energy-intensity boundary elements.
Authors: Bliss Donald , Michalis Krista , Franzoni Linda
Published: October 2013

Enclosures with diffuse reflection boundaries are modeled with an energy-intensity boundary element method using uncorrelated broadband directional sources. An absorption-based perturbation analysis shows the spatial variation of acoustic field obeys certain scaling laws. A series expansion in terms of average absorption gives separate boundary integral problems at each order. The lowest-order solution has a uniform level proportional to the reciprocal of the average absorption. The next-order solution is independent of average absorption and primarily responsible for spatial variation of the acoustic field. This solution depends on the spatial distribution of absorption and input power sources, but not their overall level. For the primary spatial variation, the effects of the relative distributions of absorption and input power are linear and uncoupled. These distributions can be expressed in terms of constituent spatial modes corresponding to the ways absorption and input power can be distributed. Solved numerically once for each mode, the acoustic field can be expressed in terms of the modal amplitudes in closed form. These amplitudes can be adjusted to tailor the spatial variation. Examples include how to distribute absorption to minimize sound levels in one location, or how to achieve a uniform interior field. [Sponsor: NSF.]
Measurement and improvement of the diffuse-reflection coefficients of profiled-wood surfaces.
Authors: Bibby Chris , Hodgson Murray
Published: October 2013

An apparatus and procedure were developed for measuring the diffuse-reflection coefficients of surfaces in an anechoic chamber according to the ISO-17497 method. This involves determining the proportion of incoherent energy in the impulse response measured in the presence of the surface. Surface absorption was measured by the reverberation-room method. The sound-absorption and sound-diffusion properties of two existing profiled-wood architectural panels, one with sinusoidal corrugations, the other comprising rectangular sections of different heights, were characterized. Investigations into how to improve the absorption and diffusion characteristics were made, and prototype surfaces tested and evaluated.
An autonomous, near-real-time buoy system for automatic detection of North Atlantic right whale calls.
Authors: Spaulding Eric , Robbins Matt , Calupca Tom , Clark Christopher , Tremblay Tremblay , Waack Amanda , Warde Ann , Kemp John , Newhall Kristopher
Published: October 2013

A moored buoy system for automatic detection of endangered North Atlantic right whale (NARW) upcalls was developed to provide near-real-time information on the presence of whales. The marine components include the WHOI buoy platform (mooring, hydrophone, power system, surface expression, and antennae) and Cornell buoy electronics (housing, analog interface hardware, GPS, embedded computer, detection engine, and telemetry hardware). Shore-side Cornell components include telemetry equipment, server hardware and processing software, database, and interfaces for data annotation, access, and visualization. The buoy hardware/software system is capable of capturing and ranking NARW upcall candidates as 2 s, 2000 Hz sampled audio clips. GPS location, timestamp, and other metadata associated with each audio clip are bundled together and uploaded via satellite for processing. Human analysts regularly annotate incoming data, resulting in a curated database of NARW detections. Periodic “health and status” data allow for confirmation that buoys are functional. Regular voltage reporting helps predict required maintenance. Following initial implementations of the system in 2005, a series of successes and failures have led to system improvements. Deployments have progressed from prototype near-shore units to an operational network continuously monitoring the shipping lanes off Boston to meet ship strike mitigation requirements. Upcoming features and capabilities will be discussed.
Right whale gunshot calls in the southeastern Bering Sea.
Authors: Berchok Catherine L. , Morse Laura J. , Clapham Phillip J. , Klinck Holger , Klinck Karolin , Mellinger David K. , Ljungblad Donald K. , Moore Sue E. , Scattorin Francesco , Keating Jennifer L.
Published: October 2013

The eastern population of the North Pacific right whale (Eubalaena japonica) is critically endangered. Following extensive historical whaling in the 19th century and large illegal catches by the USSR in the 1960’s, it is likely that this population now numbers in the tens of animals. Little is known about the distribution, movements, migrations, or habitat use of this population, but the existing data suggest that it now occupies a reduced range compared to historical times. In 2007, NMML began conducting a multiyear study of the distribution, abundance, and habitat use of North Pacific right whales in the North Aleutian Basin and southeastern Bering Sea using aerial and vessel surveys. During the 2008 survey, directional sonobuoys were used 24 h a day to record right whale calls and obtain cross-bearings to the whales. Although previous work in the Bering Sea focused on detections of the right whale upsweep call, our findings suggest that the gunshot call is much more ubiquitous. Spatial and temporal trends of gunshot calls will be presented, and changes in gunshot call characteristics relative to observed surfacing sequences will be described. [Work supported by an interagency agreement from the Minerals Management Service.]
Detection of killer whale presence using low duty cycle recorders.
Authors: Nystuen Jeffrey A. , Hanson M. Bradley , Emmons Candice , Wade Paul , Miksis-Olds Jennifer
Published: October 2013

Passive aquatic listeners (PALs) have been developed to make long-term (up to a year) autonomous measurements of the underwater ambient noise in the marine environment. Because of data storage limitations and low-power requirements, PALs have a very low duty cycle, of the order of 1 percent. In fact, they are optimized for acoustic rainfall detection and have been successfully used to measure wind speed and rainfall rate at sea using spectral components of the sound field. These geophysical sounds have relatively long time scales (minutes) compared to vocalizations of marine mammals (seconds) or mooring noise (chain clanking). Data collection was designed to detect and reject short temporal signals. However, these signals include marine mammal vocalizations. Consequently, the sampling strategy was modified to evaluate the temporal content of the data sample and save the temporal data sample only if it contains a signal consistent with killer whale vocalizations. These sound bites have demonstrated detection of pod-specific vocalizations of resident-type killer whales, transient-type killer whales, bone crunching from likely killer whale predation (eating) on sea lions, and humpback and N. Pacific right whales.
Acoustic rediscovery of right whales in a former whaling area, the Cape Farewell Ground, between Greenland and Iceland.
Authors: Mellinger David K. , Nieukirk Sharon L. , Klinck Karolin , Klinck Holger , Dziak Robert P. , Clapham Phillip J.
Published: October 2013

The North Atlantic right whale (Eubalaena glacialis) is one of the world’s most endangered cetaceans, with only 300–350 animals believed alive. Most right whales are thought to range from Florida to Nova Scotia, though the whereabouts of a significant portion of the population remains unknown in both winter and summer. Here we describe an acoustic survey for right whales near the Cape Farewell Ground, a late 18th-century whaling area. Continuously recording autonomous hydrophone instruments were deployed at five sites for one year in 2007–2008, after which data were analyzed by automatic detection with manual checking for “up” calls of right whales. Over 2000 calls were detected in all, with calls found at all sites but mostly from near the Cape Farewell Ground. The data are consistent with a seasonal migration northeastward toward Iceland in July–August followed by return movement later in the fall, with the last detection in December. At one site, calling occurred in the fall on 17 separate occasions, suggesting a significant number of right whales present. A right whale photo-identified in 2003 at the Cape Farewell Ground was not in the North Atlantic right whale catalog, suggesting the possibility of a previously unidentified stock.
Annual variability of cetacean occurrence along the northeast coast of Iceland measured using ecological acoustic recorders.
Authors: Magnusdottir E.E. , Rasmussen M.H. , Lammers M.O.
Published: October 2013

In order to continuously monitor the annual density and habitat use of cetacean species at the NE coast of Iceland, we deployed two seabed mounted ecological acoustic recorders (EARs) in Skjalfandi Bay (66 deg 05.929 N, 17 deg 25.262 W; 66 deg 03.070 N, 17 deg 39.811 W). The EAR is a microprocessor-based autonomous recorder. Each EAR was programmed to record for 1 min every 15 min. Both EARs will be retrieved every 3–5 months during a 1-year period. A custom Matlab program will be used to automatically detect and analyze target sounds. Target biological sounds recorded are primarily those produced by cetaceans and also by pelagic fish. Blue whales (Balenoptera musculus), humpback whales (Megaptera novaeangliae), minke whales (Balaenoptera acutorostrata), white-beaked dolphins (Lagernorhynchus albirostris), and killer whales (Orcinus orca) are well known to visit Skjalfandi Bay. In addition, it has been suggested that cod (Gadus morhua) is spawning in the bay in spring time. The results could reveal annual variability of inter- and intraspecies density of cetaceans and prey within the area. Acoustic monitoring may be an effective means of tracking diurnal and annual activity of cetaceans in a long-term manner and compare the activity to the presence and behavior of prey.
Information theory application to inversions of acoustic data from a continental shelf environment.
Authors: Knobles David P. , Koch Robert A. , Sagers Jason D.
Published: October 2013

This research examines the uncertainty in waveguide parameter values obtained from acoustic inversion of data collected in range-dependent environments. To account for range-dependence in the environmental parameters, the number of inversion parameters must be increased. Generally, from a fixed data sample the uncertainty in the solution for individual parameter values increases as the number of inversion parameters increases, especially if the structure of the propagated acoustic field is sensitive to the additional parameters. This effect can be offset by prior information that reduces the volume of the parameter search space and to a limited extent by larger inversion data samples. How an inversion algorithm accounts for prior information is thus an essential issue to be addressed for range-dependent waveguides. Measurements made on the New Jersey shelf in 70–90 m of water provide an opportunity to study the effects of environmental range dependence on sound propagation and inversion processing. Inversions based on pre-existing geophysical information are combined with a maximum entropy approach to quantify the amount of information on the waveguide parameters that can be extracted from measured propagation over range-dependent tracks. Both towed sources emitting CW lines and impulsive sources are employed. [Work supported by ONR.]
A simplified model of frequency distortion in ocean acoustic signals by multiple interactions with a moving ocean surface and its use in oceanographic inversions.
Authors: Lynch Stephen D. , D’Spain Gerald L.
Published: October 2013

Received omnidirectional spectra of low frequency narrowband tones measured in a shallow ocean waveguide exhibit Doppler-shifted sidebands at frequencies whose offsets are integer multiples of the dominant surface wave frequencies. These observations suggest that higher order scattering is important. However, higher-order perturbation theory involving only a single surface interaction does not predict the observed relative sideband levels. In particular, the higher order sidebands were often observed to increase in relative level to the main spectral peak during smaller surface wave, and, therefore, smaller kh, conditions. A simplified model is presented that simulates the surface wave-induced frequency distortions as path-length modulation caused by the vertical motions of the surface. The model incorporates multiple interactions with the moving surface, and quantitatively predicts the effects on the received spectra of the spatial coherence of the surface waves along the propagation path. The model results are identical to those from higher order perturbation with a single interaction. The simplified nature of this model allows it to be readily used to invert for various properties of the ocean surface wave directional spectrum. [Work supported by ONR, Code 321(US).]
Inversion for range-dependent water column sound speed profiles in shallow water.
Authors: Ballard Megan S. , Becker Kyle M.
Published: October 2013

Spatial and temporal variability of the sound speed field in the water column can have a significant impact on acoustic propagation. It is difficult or sometimes impractical to measure fine scale variations in water column properties over an acoustic propagation path. When measurements are not available, water column properties must be approximated. In past work, inverse methods based on acoustic tomography and matched-field processing have been used to estimate mean water column sound speed profiles. The drawback of these methods is their inability to capture fluctuations in the water column sound speed profile. In this work, a perturbative scheme using modal wave numbers is used to obtain range-dependent features of the water column. Based on the work of Rajan et al. (1987), a technique has been developed to estimate water column sound speed profiles using historical data to constrain the inversion. This constraint allows for a robust inversion; the result is accurate both when the inputs are noisy and when the bottom is poorly known. The new technique is demonstrated using data from the Shallow Water 2006 (SW06) experiment. Inversion results are compared to in situ measurements from the towed CTD chain. [Work supported by NDSEG and ONR.]
Investigation of an ultrasound imaging technique to target kidney stones in lithotripsy.
Authors: Shah Anup , Paun Marla , Kucewicz John , Sapozhnikov Oleg A. , Dighe Manjiri , McKay Hunter A. , Sorensen Mathew D. , Bailey Michael R.
Published: October 2013

Localization of kidney stones and targeting for lithotripsy can be challenges especially with ultrasound. However, twinkling artifact has been observed where Doppler ultrasound imagers assign color to the stone. We report a preliminary investigation from our observations in a porcine model and hypothesize why this artifact occurs. Glass beads, cement stones, and human stones were surgically placed into the renal collecting system through the ureter. The stones were imaged using several transducers and ultrasound imagers. In all cases, the twinkling artifact of the stone was observed, and its appearance and radiofrequency signature were unique from those of blood flow. Calcium oxalate monohydrate stones and smooth stones were not more difficult to image, contrary to previous reports. Increasing gain or placing the focal depth distal to the stone enhanced the artifact, but other user controls showed little effect. Twinkling started at the lateral edges of the stone and spread over the stone as gain was increased. The evidence supports the hypothesis that small motions induced by radiation force or elastic waves in the stone cause changes in received backscatter, particularly at imaging angles oblique to the stone surface. [Work supported by NIH DK43881 and NSBRI SMST01601.]
Wind turbines: Why they are noisy and what to do about it.
Authors: van den Berg Frits
Published: October 2013

Sound from modern, tall wind turbines is related to sleep disturbance and is, per decibel, more annoying than sound from common sources such as road or air traffic. Surveys among residents indicate that there are several reasons for this: the swishing character of the sound, the intrusiveness at night, and the visibility of the wind turbine(s). Residential reaction is also determined by the attitude towards wind turbines in the landscape and by economical benefits. From acoustical research different explanations have arisen as to why the sound is amplitude modulated. For a distant observer it is the result of the change in trailing sound level due to the change in wind that the revolving blades encounter. High night-time sound levels are due to an increase in rotor height wind speed simultaneously with a decrease in near-ground wind speed. Wind turbine design has been directed to higher yields per turbine. Less attention has been given to low noise blades and rotor speed reduction. Low noise design could also include a reduction in the modulation amplitude and more sophisticated speed reduction; viz., at high annoyance conditions. Also, involving residents in wind farm planning may have a high potential to reduce annoyance.
An overview of the acoustical activities at the National Wind Technology Center.
Authors: Huskey Arlinda , Patrick Moriarty , van Dam Jeroen , Simley Eric , Palo Scott
Published: October 2013

The National Wind Technology Center (NWTC) has been involved in wind turbine acoustics since the 1980s. The areas of work include standards development, measurement and analysis, prediction code development, and acoustic arrays. Most measurements are conducted to the IEC 61400-11, a standard specifically for acoustic measurements of wind turbines. The NWTC is involved in the development of this standard. The standard results in reports of overall levels as well as tonality. The NWTC has also developed a semiempirical acoustic noise prediction code for wind turbines. Validation of this code with test data (both wind tunnel and field measurements) shows reasonable prediction accuracy for both airfoil self noise and turbulent inflow noise. Lastly, to assist with wind turbine noise reduction and to identify the loudest components an acoustic array was developed to better locate noise on wind turbines. This paper will describe the NWTC’s past and current activities in wind turbine acoustics including test methods and results.
Methodologies to address limitations of the ISO9613-2 standard for wind turbine noise propagation modeling.
Authors: Kalapinski Erik J.
Published: October 2013

The accuracy of the noise propagation modeling results is dependent on: (1) the sound source data entered into the model as reported by wind turbine equipment manufacturers as specified under per IEC 64100-11 standard; (2) site specific topographical, meteorological, and terrain conditions; and (3) the propagation algorithms of the acoustic modeling standard that are applied. For wind energy facilities sited in the US, the ISO 9613-2 standard is most commonly used due to its proven effectiveness to accurately predict the sound levels at a distance for industrial and commercial projects in an outdoor environment. The propagation algorithms employed by the ISO 9613-2 standard account for geometrical divergence, atmospheric absorption, ground attenuation, screening effects, and favorable sound propagation conditions that would occur during omnidirectional downwind meteorological conditions. The purpose of this paper is to identify limitations inherent in the ISO 9613-2 standard to the specialized application of wind turbine acoustics and nonstandard atmospheric conditions. Methodologies are presented to more accurately describe atmospheric and lateral attenuation effects, which can result in significant uncertainties in the noise levels calculated both in proximity and at distant receptor locations.
A simple experiment for understanding resonant air columns.
Authors: Argo Theodore F. , Greene Chad A. , Wilson Preston S.
Published: October 2013

One goal of Project Listen Up is to enhance children’s understanding of acoustics through engagement in basic acoustics experiments. This work proposes an experiment that examines the resonant frequencies of an air column. Equipment for this experiment consists of a small tunable oscillator circuit connected to a loudspeaker, which can also be used for other experiments in the kit. The experimenter will provide a cardboard tube, rubber band, plastic wrap, and sand. Resonance is demonstrated by placing the loudspeaker at the base of the tube, covering the top of the tube with a plastic wrap membrane, and placing sand grains on top of the membrane. As frequency is adjusted, the sand grains are excited at the resonance frequencies of the tube. Frequencies at which sand motion is observed can be compared to a simple algebraic model, which relates the length of the tube to the resonance frequencies of the system. An optional advanced experimental track investigates the effect of varying the length of the tube. This experiment develops intuition for the relationship between frequency and wavelength and builds understanding of resonant systems.
Hands on and homemade coupled oscillators for Project Listen Up.
Authors: Mock Sean M. , Korman Murray S.
Published: October 2013

A coupled pendulum oscillator experiment recently developed within the U.S. Naval Academy Physics Department seems a possible candidate for the Project Listen Up initiative. A plexiglass frame supported by four legs suspends two 500 g masses 30 cm below by two chains of paper clips each, meeting in the shape of a V on either bob. A light spring (k=3.64 N/m) connects the two, completing the coupled oscillator system. Displacement of the oscillators was measured using Pasco motion sensors, a Vernier LabPro unit, and a laptop. LOGGERPRO and MATHEMATICA software helped compare theory with experiment. However, one does not need these resources to experiment with coupled oscillators—it can be improvised using ordinary household materials for young students! An inexpensive wooden picture frame with islet screws supports pendulums using two Dixie cups filled with sand or coins as masses. The possibilities for learning seem endless! A simple stopwatch, meter stick, fulcrum, and measuring cups are incorporated in experimental and theoretical comparisons, including the periods of normal modes. Students can explore density through balancing masses with volumes of water. Demonstrating beat frequencies from mistuned xylophone bars or guitar strings conveys a subtlety of the experiment without overpowering the young minds of future scientists.
Hearing loss litigation.
Authors: Dobie Robert A.
Published: October 2013

Most hearing loss in American adults is attributable to aging, noise, or a combination of these two. While most claims for noise-induced hearing loss are handled administratively in workers compensation, litigation against employers, premises owners, and manufacturers of noisy equipment continues to pose interesting challenges. Issues of negligence often involve professionals with expertise in noise control, hearing conservation program management, product labeling, and human factors. There are usually two primary issues for clinician experts: How severe is the hearing loss, and what caused it? Audiologists and otologists can draw upon a mass of research to support reasonable opinions in cases with complete data sets. Unfortunately, important data from the past (e.g., changes in noise exposure and hearing loss over a career) are often impossible to obtain. Forensic consulting is terra incognita for most clinicians, requiring analyses and judgments that are rarely called for in clinical practice.
Can race car sound break windows?
Authors: Braslau David
Published: October 2013

Sound from a special class of race cars was cited as cause for sudden breakage of a large pane of tempered glass in a private box that fell and injured a spectator below. Analysis of previously recorded race track noise from a similar track in Minnesota showed that sound levels could exceed the Hubbard rattle criteria but no conclusions could be drawn regarding breakage. Because of time constraints, sound level measurements from a race in Ohio of this vehicle class were taken by Campanella Associates for reference. Those measurements were compared with previously measured levels of other vehicle classes and found to be higher at some frequencies. Since a recorded demonstration performed by the plaintiff showed breakage of a similar pane of glass with an induced flaw and continuously applied sound at 70 to 80 Hz, a field test on a similar window with simulated sound levels based upon measurements from the special vehicle class race was performed with assistance from Synergistic Design Associates. A simulated sound level as high as 117 dBA was generated at the window without breakage. Some conclusions on potential glass breakage from incident sound will be presented. [Work supported by Johnson & Lindberg, P.A.]
Impulsive sound propagation in coastal regions.
Authors: Di Xiao , Talmadge Carrick , Waxler Roger , Gilbert Kenneth E. , Conner David A.
Published: October 2013

Influenced by the coastal temperature profile and wind profile, the resulting sound speed profiles in coastal regions have certain unique features, such as double inversion zones. As a result, long range sound propagation presents certain properties due to these features. An impulsive sound propagation experiment had been conducted in the morning hours of the summer of 2007 in the coastal Florida area. The test field was 7 km long. Three propane cannons were used during the experiment, located at each end of the test field and in the middle of the test field. Both upwind and downwind propagation data were collected and will be presented. The data showed that coastal region meteorology has a dominant effect on long range sound propagation. Simulated sound propagation results using measured meteorological data are compared with measured impulsive sound propagation data.
Calculations of wind noise underneath a foam covering at the ground surface.
Authors: Yu Jiao , Raspet Richard , Webster Jeremy , Abbott JohnPaul
Published: October 2013

A foam windscreen reduces the wind noise generated at a microphone. Similarly, a thin foam covering above a surface mounted microphone also lowers the wind noise level effectively. Recent research has focused on developing a physical model for calculating the wind noise pressure fluctuation spectrum measured by a foam covered microphone under a turbulent flow based on our current model for flush mounted bare microphones. The foam surface not only reduces the wind noise at the microphone, but also prevents direct exposure of the microphone to the flow, which reduces the measurement’s sensitivity to details of the meteorological conditions. In this talk, the calculation model will be introduced, and the comparisons between our predictions with the model and our measurements down to low wave number will be presented and discussed. [Research supported by the U.S. Army TACOM-ARDEC at Picatinny Arsenal, NJ.]
Masking period patterns of exponentially ramped and damped noises in hearing-impaired listeners.
Authors: Lentz Jennifer , Shen Yi
Published: October 2013

Noises that are modulated with either an exponentially rising (ramped), repeating modulator or a falling (damped), repeating modulator may evoke strong perceptual differences. To explore a possible cochlear contribution to these perceptual differences, masking period patterns (MPPs) of ramped and damped noises were measured for normal-hearing listeners at different stimulus levels and for hearing-impaired listeners. By time-reversing the ramped MPP, comparisons can be made between thresholds for which the masker power was the same between ramped and damped noises. Previous results showed that for normal-hearing listeners, the MPP of a ramped noise is considerably shallower than the MPP of a damped noise. The present results indicated that the differences between the damped and the time-reversed ramped MPPs were the largest at moderate stimulus levels and the smallest at low and high stimulus levels. Listeners with hearing loss exhibited no difference in the damped versus time-reversed ramped MPPs. Results will be discussed in terms of contributions of the cochlear nonlinearity and central auditory processes.