bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring the wobble of radiation field centers during gantry rotation and collimator movement on a linear accelerator
Authors: Du Weiliang , Gao Song
Published: July 2011

Purpose:

The isocenter accuracy of a linear accelerator is often assessed with star‐shot films. This approach is limited in its ability to quantify three dimensional wobble of radiation field centers (RFCs). The authors report a Winston–Lutz based method to measure the 3D wobble of RFCs during gantry rotation, collimator rotation, and collimator field size change.

Methods:

A stationary ball‐bearing phantom was imaged using multileaf collimator‐shaped radiation fields at various gantry angles, collimator angles, and field sizes. The center of the ball‐bearing served as a reference point, to which all RFCs were localized using a computer algorithm with subpixel accuracy. Then, the gantry rotation isocenter and the collimator rotation axis were derived from the coordinates of these RFCs. Finally, the deviation or wobble of the individual RFC from the derived isocenter or rotation axis was quantified.

Results:

The results showed that the RFCs were stable as the field size of the multileaf collimator was varied. The wobble of RFCs depended on the gantry angle and the collimator angle and was reproducible, indicating that the mechanical imperfections of the linac were mostly systematic and quantifiable. It was found that the 3D wobble of RFCs during gantry rotation was reduced after compensating for a constant misalignment of the multileaf collimator.

Conclusions:

The 3D wobble of RFCs can be measured with submillimeter precision using the proposed method. This method provides a useful tool for checking and adjusting the radiation isocenter tightness of a linac.
Merchant ship-radiated noise source levels.
Authors: Wales Stephen C. , Heitmeyer Richard M.
Published: July 2011

Ship-radiated noise is the principal source of noise in the 20–300 Hz frequency regime. This presentation provides a review of the issues relating to measuring ship-radiated noise source levels and predicting the source levels from ship parameters. The process of measuring and calculating the source levels is covered, including a discussion of propagation effects and source representation. Based on measurement results it is shown that, contrary to the classical model of shipping source levels, there is a negligible correlation between the source levels of an ensemble of ships and the transiting speeds and lengths of those ships. Issues concerning using the source level model in a modeling environment are discussed, including some effects of changing speed and source depth. Additionally, evidence is presented that predictions of increases in the source levels of the world’s ships based on increases in their speeds is not justified, while increases due to size (length) are not trivial. [Work supported by the ONR through NRL-base funding.]
Behavioral response of harbor porpoises to vessel noise in a tidal strait.
Authors: Polagye Brian , Wood Jason , Bassett Chris , Tollit Dom , Thomson Jim
Published: July 2011

Admiralty Inlet, a narrow channel in Puget Sound, WA, is the proposed location of a pilot tidal energy project. A pair of hydrokinetic turbines would be deployed, for evaluation, on the seabed in approximately 60 m of water. When extracting power from strong tidal currents, these turbines will also generate broadband noise. Harbor porpoises are known to exhibit strong avoidance behavior to loud noise and occur frequently in this area. Consequently, there is a concern that the project could cause local displacement of this species. Because Admiralty Inlet is a major shipping lane and traversed by a passenger ferry, there is already periodic, high intensity anthropogenic noise in the vicinity of the proposed tidal energy project. The behavioral response of harbor porpoises to these existing noise sources is evaluated to provide context for the potential impact from tidal turbine noise. This study combines data on shipping and ferry traffic from an automatic identification system receiver, received noise levels from broadband autonomous hydrophones, and current velocity from Doppler profilers. These are correlated with porpoise presence, as assessed by echolocations detected by Chelonia C-Pods. Information collected over a full year provides insight into behavior at several time scales.
Imaging and localizing fish and marine mammals with acoustics.
Authors: Ratilal Purnima , Tran Duong , Gong Roger , Reed David , Chauhan Hari , Makris Nicholas
Published: July 2011

During the 2006 ocean acoustic waveguide remote sensing (OAWRS) experiment in the Gulf of Maine, large shoals of Atlantic herring were instantaneously imaged in the frequency range from 300 to 1200 Hz. Simultaneously, several thousand instances of marine mammal vocalizations were passively recorded on a high resolution towed horizontal receiving array. A vast majority of the vocalizations were from humback whales in the 300–600 Hz frequency range. Vocalizations from other marine mammals species ranging from 40 Hz to over 3 kHz were also recorded. Various approaches are employed to localize and track the whales both passively and actively. The bearing of calling whales can be found by beamforming their vocalizations measured on the receiving array. An efficient and robust matched filter is designed to enhance the signal-to-noise ratio of the whale vocalizations. The array invariant method [Lee and Makris,  J. Acoust. Soc. Am. (2006)] is then applied for instantaneous whale range estimation. The array invariant approach has been verified theoretically with modeled complex nonlinear whale vocalizations propagated long ranges exceeding 50 km in a range-dependent ocean waveguide. The whale range estimates obtained with the array invariance technique are verified by hyperbolic localization of the vocalization signals measured by the moving receiver array along a given track.
Assessing juvenile Atlantic bluefin tuna schools in the Northwest Atlantic using sonar data and aerial imagery.
Authors: Schroth-Miller Madeline L. , Weber Tom C.
Published: July 2011

Over the past 2 years, a feasibility study has been conducted in order to establish a methodology for assessing the biomass of juvenile Atlantic bluefin tuna (Thunnus thynnus). Over several days in August 2009, a 400 kHz Reson 7125 multibeam sonar installed on a commercial fishing vessel was used to collect acoustic backscatter from tuna schools. The multibeam sonar was oriented on the starboard side of the vessel to image a vertical slice of the water column. Because the fishing vessel was led to the tuna schools by a spotter plane, we were restricted to examining only near-surface tuna schools that were visible from the air. The same spotter plane collected aerial images of the same schools that were examined with the multibeam sonar. The multibeam sonar data allowed us to estimate attributes such as the maximum depth, cross sectional area, and morphology of the fish schools in a vertical plane, while metrics such as the nearest neighbor distance and number of fish were estimated from the aerial photographs. Taken together, the sonar data and aerial imagery provide a viable methodology for assessing juvenile Atlantic bluefin tuna.
Stone comminution using histotripsy.
Authors: Hall Timothy L. , Duryea Alex P. , Cain Charles A. , Roberts William W.
Published: July 2011

This work explores the use of histotripsy to enhance urinary stone comminution ordinarily accomplished by lithotripsy. Histotripsy is a method of tissue ablation or erosion using high-energy pulsed therapeutic ultrasound to induce and control a cavitation bubble cloud. We have shown previously that histotripsy applied to model urinary stones causes surface erosion producing fine debris, which can be more readily eliminated. In this work, we show that optimal acoustic parameters can yield an effective comminution rate (96 mg/min) similar to a standard lithotripter (111 mg/min). As histotripsy is a surface erosion effect within the cloud of cavitation bubbles and lithotripsy has been shown to be most efficient at initial coarse fragmentation of stones, we propose a combined approach where the lithotripter coarsely fragments the stone, while histotripsy is used to erode these fragments with their greatly increased surface area.
Clinical assessment of shockwave lithotripsy accuracy.
Authors: Shah Anup , Harper Jonathan D. , Wright Jonathan L. , Sorensen Mathew D. , Paun Marla , Bailey Michael R.
Published: July 2011

Kidney stone movement primarily due to patient respiration compromises shock wave lithotripsy (SWL) targeting and efficacy. The objective of this study is to describe the use of B-mode ultrasound to evaluate the accuracy of targeting during SWL. Patients undergoing electrohydraulic SWL were enrolled into this institutionally approved research study. A commercial diagnostic ultrasound imaging system, either Philips HDI 5000 or iU-22, was used to intermittently visualize and detect any shockwave-induced motion of the stone during 1–3 min periods. Four patients (mean age 52.7) underwent treatment of seven renal stones with mean individual stone size of 10.41 ± 4.5 mm. A mean of 2937 shocks (range 2750–3000) were delivered at a rate of 1–2 Hz and charging voltage of 14–26 kV. Stone oscillation or jumping at the exact time of individual shock delivery was visualized with ultrasound: no stones completely failed to move. Accurate alignment, as interpreted by positive stone motion, occurred in a mean of 50 ± 20.4% of shockwaves. Ultrasound imaging represents a method of real-time assessment of accuracy in SWL and may provide the basis for devices to control targeting so that shockwaves are only delivered when the stone is in focus. [Work supported by NIH DK43881 and DK086371.]
Overview of an indoor sonic boom simulator at NASA Langley Research Center.
Authors: Klos Jacob , Loubeau Alexandra , Rathsam Jonathan
Published: July 2011

A facility has been constructed at NASA Langley Research Center to simulate the soundscape inside residential houses that are ensonified by environmental noise from aircraft. The purpose of this facility, the interior effect room, is to examine parameters that affect psychoacoustic response in a controllable indoor listening environment. The single room facility, built using typical residential construction methods and materials, is surrounded on two sides by arrays of loudspeakers. These exterior arrays are used to simulate aircraft noise sources that transmit into a room of a typical house. The exterior sound reproduction system, which consists of 52 subwoofers and 52 mid-ranges in close proximity to the walls of the room, has been designed to enable study of sonic booms transmitted into residential structures and has a usable bandwidth of 3 Hz–6 kHz. In addition to these exterior arrays, satellite speakers placed inside the room are used to simulate rattle and other audible contact-induced noise that can result from low frequency excitation of a residential house. The layout of the facility, operational characteristics, acoustical characteristics, and equalization approaches are summarized. Current research efforts utilizing the facility are described in two companion papers.
Quasispherical acoustic resonators: The shell-gas interaction.
Authors: Mehl James B. , Moldover Michael R.
Published: July 2011

Spherical acoustic cavity resonators are useful tools for high-precision measurements of the speed of sound in gases. Conventionally, the gas-acoustic resonances are corrected for coupling to the shell using analytic expressions valid for isotropic, unsupported, shells of uniform thickness. Practical resonators have nearly spherical inner surfaces but exterior surfaces with non-spherical features and support structures. Finite-element methods have been used to calculate the response of realistic resonator shells that are coupled to support structures. Improved corrections of the gas-mode eigenfrequencies can be obtained in a form that is similar to the usual analytic expression, except that the shell response function must be calculated numerically. It is also shown that the coupling of gas modes through the shell is normally a weak effect proportional to the square of the static pressure and is totally negligible except in very unusual circumstances. The evolution of gas-shell coupling is followed when the speed of sound in the gas is varied so that a radial gas mode eigenfrequency fg approaches a shell mode eigenfrequency fs. The gas mode becomes unobservable as fg nears fs due to an avoided-crossing phenomenon similar to simple coupled oscillators.
Auditory filter with minimum-uncertainty product between frequency and scale.
Authors: Keefe Douglas H.
Published: July 2011

A scale representation of a signal describes its compression or dilation as a function of time or frequency. Because the frequency scaling properties of cochlear mechanics vary slowly at frequencies above 1–1.5 kHz, a frequency-scale representation is of particular interest for auditory filters. An auditory filter is constructed based on the analytic signal with the minimum uncertainty product between frequency and scale. Its spectral and temporal properties are analyzed. The complex spectrum of the filter is completely specified as a function of the frequency relative to the center frequency of the filter, the filter $Q,$ and the dimensionless group delay normalized by the number of periods at center frequency. In approximate agreement with basilar-membrane mechanics and human psychophysics, the frequency of peak spectral amplitude decreases by a half octave as tuning broadens, the spectral amplitude gain increases with sharper tuning, and the dimensionless group delay of the filter is independent of frequency. The peak envelope of the filter impulse response occurs at a time inversely proportional to the peak spectral frequency. Results are obtained on auditory phase perception for tones embedded in chirp maskers. A nonlinear filterbank composed of frequency-scale filters has potential applications in auditory research and audio engineering.
Subjective evaluation of across-frequency delays.
Authors: Wojtczak Magdalena , Beim Jordan A. , Oxenham Andrew J.
Published: July 2011

Basilar-membrane filtering introduces frequency-dependent cochlear delays. Cochlear models predict that the delay between the peaks in responses to 100-Hz versus 10-kHz tones may be as long as 10 ms. This study investigated the role of across-frequency delays for asynchrony perception. A method of constant stimuli was used to evaluate the perception of delays between two tones, a 250-Hz tone paired with a higher-frequency tone at 1, 2, 4, or 6 kHz for a range of delays between the high- and low-frequency tones. Bandpass noise located between the two tones was used to avoid within-channel cues. Listeners judged whether the tone pairs appeared synchronous or asynchronous. For each pair, the proportion of “synchronous” responses was plotted as a function of the delay between the tones. Since cochlear-filter bandwidths depend on level, the perception of across-frequency delays was evaluated for two levels of the tones, 20 dB SL and 85 dB SPL. Overall, the data support the hypothesis of a higher-level mechanism compensating for cochlear delays, producing veridical perception. However, the results do suggest a perceptual asymmetry, with synchronous judgments occurring more often for leading high-frequency tones than vice versa. [Work supported by NIH Grant No. R01DC006804.]
Discrimination of acoustic differences improves with greater dissimilarity to experienced covariance.
Authors: Stilp Christian E. , Kluender Keith R.
Published: July 2011

Stilp et al. [Proc. Natl. Acad. Sci. (in press)] demonstrated efficient coding of correlations between complex acoustic attributes (attack/decay and spectral shape) in novel sounds. Discrimination of differences between sounds that violate correlations (orthogonal) is initially inferior and later comparable to that for sound pairs that respect the correlation (consistent). Subsequent findings [Stilp et al., J. Acoust. Soc. Am. 128, 2455–2456 (2010)] suggest that this effect may depend more on acoustic similarity between consistent and orthogonal sounds than upon probability of orthogonal test trials. Across the present experiments, listeners discriminated (AXB) the same 15 consistent sound pairs and a single orthogonal sound pair of varying similarity to the consistent sounds (distance from the correlation vector in the stimulus matrix). Orthogonal discrimination systematically improves with increasing dissimilarity. With extreme dissimilarity, orthogonal discrimination is significantly better than consistent discrimination across all testing blocks. Results cannot be explained by weighting of individual stimulus dimensions. A principal components analysis network model for extracting covariance structure that successfully predicted listener performance in previous tasks predicts some but not all of these findings. Implications for perception of complex sounds including speech will be discussed. [Work supported by NIDCD.]
Effect of internal pressure on the vibrational response of fluid-filled shells: Finite element model.
Authors: Abdul-Wahid Sami , Piacsek Andrew A.
Published: July 2011

A finite-element model of the vibrational response of fluid-filled shells with arbitrary shape and composition has been developed using the COMSOL multi-physics modeling package. The user can specify the properties of the fluid inside the shell including the static pressure. The shell is surrounded by air, which is enclosed by a perfectly matched layer boundary, and an acoustic source is positioned just outside the shell. The frequency response of the shell due to a swept sine acoustic excitation can be recorded at multiple locations. Model results for a spherical aluminum shell filled with water at different static pressures are compared with experiment. Results are also shown for a shell with geometry and material properties similar to a human skull. The goal is to apply this model to predict vibrational response due to changes in intracranial pressure. [Work supported by Central Washington University Science Honors Program.]
An efficient back-scattering model for arbitrarily shaped objects.
Authors: Pees Edward
Published: July 2011

A method is presented for efficiently computing the propagating pressure field back-scattered from arbitrarily shaped, 3-D objects. This is accomplished by drawing upon a previously reported relationship between the boundary condition on a 2-D radiating aperture and the pressure propagating along an axis normal to the aperture, and the diffraction slice theorem, which relates the Fourier transform of an object function to its scattered pressure field. Together, these two results allow for the derivation of an integral formula that expresses the pressure field back-scattered from an object as a 1-D Fourier transform of its scattering amplitude. Use of this formula is demonstrated for computing the back-scattered pressure field from a uniform sphere in the first Born approximation (weak scatterer) and with a Kirchhoff boundary condition (rigid scatterer); the results of which are compared to the corresponding rigorous partial wave expansions.
Stability of unconsolidated sediments and acoustic transmission.
Authors: Lowrie Allen
Published: July 2011

The degree of compaction in marine sediments has a direct effect on their velocity and density, components in the Navy’s geoacoustic databases. Acoustic transmission through sediments necessitates grain-to-grain contact. Such a conceptual model coincides with geology of sediments settling onto seafloor to consolidation as generally continuous. However, such continuity may not be justified. Understanding of global/regional/local processes and impacts suggests that sediment grains are jostled, causing rearrangement/breaking/damaging/retarding contact between grains, reducing rigidity, and intergranular fluids “flushed” by passing ocean waves. Resultant of these processes is that sediments remain unconsolidated to unexpected depths. Improved knowledge of global/regional/local stress-fields reveals heretofore unappreciated complexity maintaining individual grains apart with retardation of contact. Meteor impacts and major earthquakes and volcanic eruptions form “instantaneous” stress-waves that can jostle sediments globally, forcing high-frequency inter-granular motions, rupturing, and interstitial fluid movements. Dynamic sedimentation episodes from glacial-lake releases and continental margin collapses provide lower frequency stress-waves causing lateral motions among sediments, re-forming grain arrangements. Wave migration over seafloor and de-watering fluctuates inter-granular fluids, maintaining interstitial spaces open. Tectonics form faults/breakages along with movements and fluids and material flowage, creating differing domains/units within sediments. These dynamic inputs within a complex-geographic-matrix assist in maintaining sediments unconsolidated.
Geological processes affecting high-frequency acoustics.
Authors: Briggs Kevin B.
Published: July 2011

Two seafloor properties that control high-frequency (greater than 10 kHz) acoustic scattering from and propagation into the sea floor are interface roughness and sediment inhomogeneities. Geological processes that affect the statistical distribution of these properties include sediment transport and sediment diagenesis. Sediment transport is a hydrodynamic process driven by waves and currents, which are results of storms and tides. Seafloor features that are significant for acoustic scattering and are created by sediment transport include sand waves, ripples, ripple-scour depressions, lag layers, flasers, and sand lenses. Scattering from these features can be predicted from the statistical characterization of interface roughness and sediment inhomogeneities. Sediment diagenesis is a physical, chemical, and sometimes biological process that affects the sediment bulk density through processes of dewatering, consolidation, precipitation, or cementation. Sediment diagenesis affects the gradient and fluctuations in bulk density and thus the speed and attenuation of sound. Scattering model inputs related to these features are derived from measurements of vertical fluctuations of sediment bulk density and sound speed. Examples of how sediment transport and diagenetic processes affect high-frequency acoustic bottom-interactions are presented.
Acoustic performance of an installed real-time three-dimensional audio system—Part II.
Authors: Faller Kenneth J. , Rizzi Stephen A. , Aumann Aric R.
Published: July 2011

The exterior effects room (EER), located at the NASA Langley Research Center, was recently upgraded to allow for simulation of aircraft flyovers in a three-dimensional (3-D) audio and visual environment. The 3-D audio server employs an implementation of the vector base amplitude panning (VBAP) method to position virtual sources at arbitrary azimuth and elevation angles in the EER. Recent work focused on the development of loudspeaker equalization first using high order FIR filters [POMA 9 015004 (2010)], and later using low order IIR filters [J. Acoust. Soc. Am. 128 2482 (2010)]. The latter, in conjunction with full-path time delay compensation and relative gain compensation, were implemented in real-time and shown to reproduce the desired sound field to within about ±5 dB over an extended frequency range for stationary and moving sources. In the present work, the performance is further characterized both objectively and subjectively. Addressed are calibration of the system for absolute sound pressure level reproduction and measurement of the spatial uniformity of the generated sound field. Further, localization of sound sources will be subjectively measured to assess the efficacy of the VBAP implementation in the EER.
Assessing cumulative impacts of underwater noise with other stressors on marine mammals.
Authors: Wright Andrew J. , Weilgart Lindy
Published: July 2011

Cumulative impact assessments (CIAs) are an often unmet requirement in many environmental impact assessment processes. However, marine mammals are typically exposed to multiple human activities and pollutants including noise, which can combine in various ways including through chronic stress responses. To address the issue, the Okeanos Foundation held an international, multi-disciplinary workshop in Monterey, CA (August 2009). Participants considered three aspects: how currently available tools for regionally mapping several anthropogenic pressures on the environment could be applied to species management, how the reported consequences in marine mammals of exposure to these pressures and their known interactions within an individual could be modeled, and how population modeling could include cumulative impacts. Participants felt that all three approaches could be realized in certain data-rich marine mammal populations, which could then be used as examples for informing management decisions in other marine mammals. The population modeling for cumulative impacts on Western gray whales and Southern and North Atlantic right whales is currently underway. Participants believed that marine spatial planning would facilitate better CIAs and that reducing ocean noise is an achievable goal that will help marine life cope with less tractable threats such as climate change.
The effects of noise on birds.
Authors: Dooling Robert J.
Published: July 2011

The effects of noise on birds can be considered as falling into four overlapping categories: hearing damage and permanent threshold shift (PTS) from acoustic overexposure, temporary threshold shift (TTS) from acoustic overexposure, threshold elevation and masking of important biological sounds, and finally, any other physiological and behavioral responses that might occur to a novel sound that is sufficiently above the natural background noise level so as to be detectable. In the first three cases at least, auditory effects depend strongly on the level and duration of noise exposure, which is highly correlated with the proximity of the bird to the noise source. Drawing on both laboratory and field data, the current state of knowledge in the field is summarized. In addition, this review will identify general principles and important exceptions, clarify and define the potential adverse effects, and suggest future approaches to understanding the effect of noise on acoustic communication in birds in their natural enviroment. [Work supported by the NPS.]
Assessing the effects of mid-frequency sonar on beaked whales in Southern California.
Authors: Melcon Mariana L. , Cummins Amanda J. , Simmonis Anne E. , Baumann-Pickering Simone , Roch Marie , Wiggins Sean M. , Hildebrand John A.
Published: July 2011

Naval exercises include the use mid-frequency active (MFA) sonar, which emits high intensity sound to obtain an acoustic picture of the environment. Little is known about the effects of MFA sonar on cetaceans, but correlations were observed between naval exercises and anomalous massive strandings of beaked whales. Passive acoustic monitoring was used to start studying the possible impact of MFA sonar on beaked whales. For this, high-frequency acoustic recording packages were deployed to continuously record sounds between 10 Hz and 100 kHz. First, the probabilities of beaked whales given MFA or no-MFA were calculated for one site in the Southern California Bight. The acoustical presence of the animals was 50% or less when MFA was present compared to the no MFA situation. Furthermore, the proportion of time with beaked whale calls decreased proportionally to the intensity of sound in the frequency band of MFA sonar. Finally, the acoustic presence of beaked whales and the intensity of mid-frequency noise at five different sites of the Southern California Bight were analyzed for 1.5 years. Possible effects of MFA sonar on these animals will be discussed as a function of exposure and geographical movements.
Behavioral response of Australian humpback whales to seismic surveys.
Authors: Cato Douglas H. , Noad Michael J. , Dunlop Rebecca A. , McCauley Robert. D. , Salgado Kent Chandra P. , Gales Nicholas J. , Kniest Hendrick , Noad John , Paton David
Published: July 2011

The first of four major experiments in project behavioural response of australian humpback whales to seismic surveys (BRAHSS) was conducted on the east coast of Australia in September and October 2010. The project aims to understand how humpback whales respond to seismic surveys and to provide the information that will allow these surveys to be conducted efficiently with minimal impact on whales. It also aims to determine how the whales react to ramp up or soft start, and to assess how effective this is in mitigation. The 2010 experiment used a single air gun. Four air guns will be used in the next two experiments and a full seismic array in the final experiment in 2013. During the 2010 experiment, behavior and tracks of whales were recroded by four theodolite stations on elevated coastal positions and DTAGs used on some whales. Vocalizing whales were tracked with a wide base line hydrophone array. A further four acoustic recorders were used to measure propagation loss and to characterize the sound field throughout the area. A wide range of variables likely to affect whale response was measured. [Work sponsored by the JIP E&P Sound & Marine Life and Bureau of Ocean Energy Management, Regulation and Enforcement.]
Examining the biosonar process involved with depredation of black cod by sperm whales in the Alaskan long line fishery.
Authors: Au Whitlow W. L. , Thode Aaron A. , Folkert Kendall , Straley Jan
Published: July 2011

The long line fishery of bottom dwelling black cod or sablefish has been plagued by depredation by sperm whales as the long lines attached to the array of hooks and caught fish are being hauled up by the fishing boat. The whales are probably attracted to a fishing boat by sounds associated with the boat being jockeyed into position so that the long line can be hauled up in a near vertical orientation. The sperm whales use their biosonar to localize and take the hooked black cods as they are being hauled up. In order to study the biosonar process, acoustic backscatter of several black cod specimens was measured using a simulated sperm whale biosonar signal having a peak frequency of 22 kHz as the specimens were rotated along both the lateral and dorsal planes. The backscatter of a rockfish (Sebastes sp.), a typical fishing hook, and a length of fishing line was also measured. The echo structure of black cod specimens allows sperm whales to discriminate between black cod, fishing hook, fishing lines, and by-caught rockfish. The target strength based on the incident and reflected energies varied from -27 to -37 dB for the black cod specimens.
Interpreted acoustic ocean observations from Argo floats.
Authors: Nystuen Jeffrey , Riser Steve , Wen Tim , Swift Dana
Published: July 2011

While it is technically possible to record high bandwidth ambient noise, practically the ocean ambient sound data need to be subsampled and interpreted for users. A new configuration of Argo float has been augmented with passive aquatic listener (PAL) technology to monitor the ocean ambient sound during the drift phase of the Argo float mission, typically at 1000 m depth for 10 days at a time. These ocean ambient sound data are interpreted as wind speed, rainfall rate, and marine animal detections. These data are reported to users via two-way iridium satellite communication link when the float surfaces at the end of each dive cycle. Changes in sampling strategies can be implemented if desired. The first set of these floats has been deployed and additional deployments are ongoing. The data will be used to study the fresh water cycle of the ocean as part of the NASA Aquarius/SAC-D satellite mission scheduled to be launched this year.
Exploring an under-ice ocean cavity with sound.
Authors: Worcester Peter F. , Munk Walter H. , Cornuelle Bruce D. , Dzieciuch Matthew A. , Wage Kathleen E.
Published: July 2011

Sensible predictions of the future rise in sea level require an understanding of the melting processes underneath the floating ice sheets of Antarctica and Greenland. Acoustic transmissions into the ocean caverns underlying the ice sheets could provide time series of temperatures and currents to augment intermittent measurements by instruments lowered through the ice and carried on autonomous underwater vehicles. The wedge of diminishing height formed between the underside of the ice and the shoreward sloping seafloor will horizontally refract sound transmitted into the ocean cavern by a source seaward of the ice edge. Incoming rays come to a coastal turning point near the grounding line of the ice sheet before returning seaward. A highly idealized model of vertical mode structure and horizontal ray structure provides estimates of the transmission paths in the wedge. In the ideal case, source-receiver separations of order 100 km for the broad Antarctic ice sheets are expected to provide good coastal returns, but separations of order 20 km for the narrow Greenland floating ice tongues are expected to result in severe reflection losses at the coastal turning points. Receivers lowered through the ice would provide valuable additional information. Further calculations using realistic propagation models are essential.
Ocean state estimation and basin-scale acoustic thermometry.
Authors: Menemenlis Dimitris
Published: July 2011

This presentation describes a global ocean state estimation system and explores the role that sustained basin-scale acoustic thermometry can play in evaluating and constraining the resulting ocean state estimates. The state estimation system is that developed by the ECCO2 project. Solutions are based on an eddying, full-depth ocean, and sea ice configuration of the Massachusetts Institute of Technology general circulation model. Data constraints include altimetry, hydrography, sea surface temperature, and satellite observations of sea ice extent, thickness, and velocity. Green’s functions and the adjoint method are used to adjust initial and surface boundary conditions and empirical parameters such as vertical diffusivity, albedos, and drag coefficients, in order to reduce model/data discrepancies. Early prototype basin-scale estimation systems that used acoustic data were deployed in the Eastern Mediterranean for THETIS-2 and in the North Pacific for ATOC. More recently, 1 decade of North Pacific acoustic thermometry data was compared with ocean simulation and estimation results. The comparisons with acoustic data provide stringent tests of the time mean hydrography and of the large-scale temperature variability in the models. The differences are sometimes substantial, indicating that acoustic thermometry data can provide significant additional constraints for numerical ocean models. Of particular interest is the deployment of a basin-scale acoustic array for monitoring changes in the deep ocean interior.
Full-diffraction and parabolic axisymmetric numerical models to characterize nonlinear ultrasound fields of two-dimensional therapeutic arrays.
Authors: Khokhlova Vera A. , Yuldashev Petr V. , Averiyanov Mikhail V. , Bessonova Olga V. , Sapozhnikov Oleg A. , Bailey Michael R.
Published: July 2011

Numerical modeling has been shown to be an effective tool to characterize nonlinear pressure fields for single-element HIFU transducers, but it has not yet been applied for the much more complex three-dimensional (3-D) fields generated by therapeutic phased arrays. In this work, two approaches are presented to simulate nonlinear effects in the field of a 256-element focused array. A new full-diffraction approach includes rigorous 3-D simulations of the nonlinear wave equation with a boundary condition given at the elements of the array. A second simpler approach is based on the KZK model and a focused piston source as the boundary condition. The effective aperture and initial pressure of the piston source are set by matching linear simulations of the two models in the focal region. It is shown that as output power is increased, agreement in the focal waveforms of the two simulations, even when shocks were present, is maintained up to very high power outputs of the array. These results demonstrate the feasibility of using the simplified KZK model to evaluate the role of nonlinear effects in the fields of two-dimensional (2-D) phased arrays of clinical devices. [Work supported by NIH Grant Nos. EB007643 and RFBR 09-02-01530, and NSBRI through NASA Grant No. NCC 9-58.]
Understanding changes in tissue phantom material properties with temperature.
Authors: Dunmire Barbrina L. , Kucewicz John C. , Mitchell Stuart B. , Crum Larry A. , Sekins K. Michael
Published: July 2011

Phantoms used for high intensity focused ultrasound (HIFU) applications require rigorous evaluation of material properties since, locally, the material experiences extreme changes in temperature and stresses with the HIFU treatment. Here we present the testing of an agar/gelatin phantom intended for both acoustic radiation force imaging (ARFI) and HIFU applications. The phantom shear modulus, speed of sound, attenuation, and thermal properties were all evaluated over the range of room temperature to 80 °C. With the exception of the thermal properties, all measurements were taken during both heating and cool down. Cavitation threshold and melting point were also tested. The change in material sound speed and thermal properties with temperature were quasireversible and similar to that of water. Material attenuation showed a slight decrease with temperature, but appeared to also be reversible. Shear modulus decreased significantly with temperature, going to near zero. The response was not reversible, returning to only approximately one-third of the starting value. These results demonstrate the complex material response that can occur with HIFU treatment. The results also raise the question of how well the test procedures, and thus results, properly reflect the true HIFU conditions. [This work was supported by the DARPA (Grant No. HR0011-08-3-0004).]
Real-time acoustic dosimetry for focused ultrasound surgery.
Authors: Jeon Jae Chun , Yoon Suk Wang
Published: July 2011

Real-time acoustic dosimetry was investigated with acoustic attenuation and sound speed variation for focused ultrasound surgery (FUS). Bovine liver was used for the study because of its acoustic similarity to human liver. Acoustic attenuation and sound speed were measured in vitro with a pulse transmission method at the frequency of 1 MHz during FUS treatment on bovine liver. In bovine liver, acoustic attenuation and sound speed were increased with increasing temperature. Acoustic attenuation was steeply increased when the temperature of the tissue was increased around 55 °C. Once the tissue was necrotized, its acoustic attenuation was not returned to its initial value even though it was cooled down to the initial temperature, while its sound speed was almost returned to its initial value. This study indicates that acoustic dosimetry with acoustic attenuation can be very feasible for real-time FUS dosage control. [Work supported by Faculty Research Fund, Sungkyunkwan University 2010.]
Proposed standard-Guidance for Developing State Noise Regulations and Local Noise Ordinances.
Authors: Brooks Bennett M.
Published: July 2011

The American National Standards Institute (ANSI) Accredited Standards Committee S12 (Noise) Working Group (WG) 41 has been developing a draft standards document for over 10 years. The current document is now in draft 8, currently under development. This document represents the consensus of many stakeholders in the community noise arena, including industry, government, consulting, and the public. The purpose of the document is to provide guidance to government officials, acoustical consultants, and other interested persons on how to develop a community noise ordinance or regulation, which is appropriate for the existing local circumstances. The document addresses issues such as public and government priorities and values, and available resources, and also provides the technical basis to manage the local sound environment. The keys to the effectiveness of the document are that it provides a menu of options for the user, discusses the trade-offs involved for decisions that must be made by government officials, and emphasizes that enforcement of a community noise ordinance is crucial to its success. A description of the current draft is presented.
Lessons learned in noise control the public sector.
Authors: Timmerman Nancy S.
Published: July 2011

The author spent 15 years as Noise Abatement Officer at Logan International Airport, installing a state-of-the-art Noise Monitoring System and answering complaints from the public about aircraft noise. The airport has been a leader in soundproofing for homes, in restricting noisy aircraft, and in providing information to the public about noise from aircraft operations. The author currently is a self-employed consultant, and recently testified about aircraft noise at a public hearing. This presentation will address the inter-relationship between the (complaining) public, the technical consultants, and the government. It will reveal some uncomfortable truths about each sector, and warn about “being careful what you wish for.”
Washington state noise laws, traffic, and finding a quieter medium.
Authors: Sexton Tim , Laughlin Jim
Published: July 2011

Washington State is actively involved with community noise, especially roadway noise, and is involved in developing outdoor alternative noise evaluation techniques and implementing community noise reduction strategies where applicable. In this presentation Tim Sexton and Jim Laughlin will discuss the current status of Washington State noise law, regulation, transportation policy, and various methods for approaching community concerns where the propagation of noise is difficult to model and even tougher to reduce. Examples include the Interstate 5 Ship Canal Bridge in Seattle, the Tacoma Narrows Bridge, quieter pavement research, construction noise in relation to local city and county noise ordinances, and preliminary work with local cities and counties on noise compatible land use.
Seattle Nightlife Advisory Board addresses the issue of urban core nightlife noise.
Authors: Wiebusch Julie A.
Published: July 2011

Urban Core neighborhoods are gaining in popularity. Infill or adaptive reuse projects are creating inner city housing and supporting a sustainable lifestyle. These neighborhoods have created walkable communities, with pedestrian-accessible amenities and proximity to the workplace. Nightlife is also often a component of an Urban Core community. Seattle has embraced expanding residential areas into the downtown core. The conflict between the residential desire for an environment that does not intrude on quieter living activities and the commercial desire to promote a vibrant nightlife within the city becomes more critical. In 2007, the Seattle Mayor signed an ordinance addressing amplified sound from nightlife. The Seattle City Council subsequently appointed a Nightlife Advisory Board (NAB) to advise the city on a number of issues relating to nightlife and noise. The NAB consisted of three nightclub owners, three residents, a police officer, a representative from the Liquor Control Board, and a noise expert. NAB collaborated to reach consensus regarding allowable sound levels, protocol for measuring the sound, and proposed modified Ordinance language. The findings were presented to the City Council and are currently under consideration.
Dissonant resonant modes of bottle-shaped thermoacoustics engines.
Authors: Andersen Bonnie
Published: July 2011

A key component of a standing-wave thermoacoustic engine is the resonator. A simple half-wave resonator is not ideal, due to the loss of energy to the higher harmonics. Cylindrical resonators with regions with differing cross sections have been shown to have overtones that are not harmonics of the fundamental. For resonators composed of two adjoining concentric cylinders with two different radii, the half-wave resonant harmonics that would be present if the radii were equal are altered. In particular, it is shown that the cylinder with the smaller radius that opens into the larger cylinder has a quarter-wave resonator effect, while the larger-radius cylinder has a half-wave resonator effect. Graphs of the resonant frequencies, found numerically, plotted as a function of one geometric parameter of the resonator, show that the frequencies bend toward the asymptotes created by these quarter-wave and half-wave influences and that where the asymptotes cross is where the dissonance is the greatest. Experimental results follow the model presented.
Intensive acoustic wave propagating in the stratified atmosphere and acoustical influence on the atmosphere state.
Authors: Gusev Vladimir A. , Zhostkov Ruslan A.
Published: July 2011

The analytical solutions describing intensive wave propagation in the stratified atmosphere are found. The exponential increase of amplitude due to stratification and change of effective viscousity are taken into account. The evolution of the initial periodic signal and the single impulse is investigated. The main attention is payed to the fine structure of shock front. The analysis of the qualitative features of evolution of both initial signals is made. The influence of the atmosphere temperature dependence on the height from Earth surface is investigated. It is shown that the strong temperature rise at large heights leads to the increase of distance of wave propagation. The obtained analytical solutions are used for estimation of intensive wave influence on the atmosphere state at large heights.
A perceptual-learning deficit in adults with reading disorders interpreted as evidence of a developmental delay.
Authors: Wright Beverly A. , Huyck Julia J. , Aliyeva Carmen
Published: July 2011

Individuals with reading disorders have difficulty reading despite having normal intelligence. Many also exhibit a number of auditory perceptual deficits. According to one proposal, these deficits arise because perceptual development in these individuals is delayed in childhood and then halted, for skills on which improvements would normally continue into adolescence, around age 10 (presumably due to brain changes associated with puberty). If so, perceptual skills with long developmental courses should be impaired in adults with reading disorders. While perceptual development is typically examined through naive performance, this prediction was tested here using a perceptual-learning paradigm. Ten adults with reading disorders were trained on a temporal-interval discrimination task using a multiple-session training regimen known to yield learning reliably in adults, but rarely in adolescents [Huyck and Wright, Developmental Science (in press). Seven of the ten did not improve with training. Thus, the response to training in the adults with reading disorders more closely resembled that of adolescent than of adult controls. This result is consistent with the idea that perceptual development may be delayed and then halted in individuals with reading disorders and highlights prolonged maturational changes in a perceptual skill other than naive performance.