bluuebunny/crossref_metadata_2025 huggingface dataset:
Single-mode field excitation experiment in shallow water
Authors: Zeng Juan , Peng Da Yong , Zhao Wen Yao , Li Hai Feng , Liu Hai Jun
Published: November 2016

Single-mode field has advantages in active detection, underwater communication, bottom backscattering measurement, etc. Some of papers have reported on the theory and simulation about the single-mode excitation by open- and closed-loop methods, respectively. The experiment in the tank has also been reported many years ago, but the experiment in the water has not been reported yet. In this paper, an effective closed-loop method for exciting the single-mode field is discussed, which can obtain the optimum estimation of the matrix of the Green’s function in the shortest feedback times, with high efficiency of emission of the single-mode signal. The experiments at the different sites in different seasons are reported. The vertical source array with the center frequency at 700 Hz was used as the source in the experiment. The experimental results show that when the source array spans almost the effective water depth the single-mode field with high quality can be excited. The first three single modes were excited at the sites with the water depth of 14 m and 36 m respectively. The experimental results show that more than 97% of the energy of the received field is concentrated in the single-mode.
Acoustic experiments over the South China Sea upper-slope sand dunes
Authors: Chiu Ching Sang , Chiu Linus Y. , Chen Chi-Fang , Yang Yiing Jang , Wei Ruey Chang , Ramp Steven R. , Miller Chris , Reeder D. Benjamin , Chang Andrea Y.
Published: November 2016

A series of experiments were methodically carried out between 2012 and 2014 to study the impact of large underwater sand dunes and the combined impact of these sand dunes and large-amplitude nonlinear internal waves on sound propagation over the upper continental slope including anisotropic propagation characteristics and focussing/defocussing scattering phenomena. The spatial distribution and scales of the sand dunes were first mapped by two multibeam echo sounding (MBES) surveys in 2012 and 2013. The 2013 experiment also provided some coring and initial acoustic transmission data to give useful knowledge of the geoacoustic properties of the sand dunes based on forward propagation modeling and least-squares fitting to the measured levels. The 2014 experiment was more comprehensive, entailing the deployment of autonomous mobile sources, a towed source and a moored source transmitting signals in different frequency bands and different geometries to a vertical line hydrophone array. Our data analysis results, aided with modeling interpretations, have provided physical insights into the observed spatial and temporal propagation characteristics. These results will be highlighted in this presentation. [The research is jointly sponsored by the Taiwan MOST and the US ONR.]
Nonlinear internal wave characteristics during the Sand Dunes 2014 acoustic propagation experiment
Authors: Ramp Steven R. , Yang Yiing Jang , Chiu Ching-Sang , Bahr Frederick L.
Published: November 2016

The Sand Dunes 2014 field experiment in the South China Sea was located in a region frequented by large amplitude (40-80 m) nonlinear internal waves. Four moorings spanning 386-266 m across the slope near 21° 52’N, 117° 36.5’E observed wave arrival patterns during June 3-19, 2014, that were similar to those previously observed nearby consisting of large (a-waves) arriving diurnally with smaller (b-waves) in between, with all amplitudes modulated by the fortnightly tidal beat. Small waves continued to gain amplitude as they shoaled, whereas large waves maxed out near 342 m then became smaller between 342 and 266 m. The number of waves/packet increased upslope due to wave dispersion. With just one exception, wave breaking and trapped cores were not observed. This contrasts with previous observations to the southwest near Dongsha Island where the wave energies (550 vs. 300 MJ) and bottom slopes were larger. Most of the incident waves can be attributed to remote forcing in the Luzon Strait, although some b-waves were formed locally due to convergence of the internal tide. A new result was the arrival of double a-waves two hours apart near spring tide on June 16-19. Some possible forcing scenarios for these double a-waves will be presented.
Observations of acoustic propagation and geoacoustic inversion affected by subaqueous sand dunes in the South China Sea
Authors: Chiu Linus , Chang Andrea , Reeder Davis B. , Chiu Ching-Sang , Yang Yiing-Jang , Chen Chi-Fang , Wang Chau-Chang
Published: November 2016

The large subaqueous sand dunes are expected to affect underwater acoustic propagation. Very large subaqueous sand dunes on the upper continental slope of the northern SCS were discovered in water depths of 160 m to 600 m, which composed of fine to medium sand. In this talk, serial acoustic experiments conducted by Taiwan and United States in the South China Sea during 2012-2014 are overviewed and mid-frequency propagation data/model as well as mid-frequency geo-acoustics are aimed. For mid-frequency propagation, results demonstrate that subaqueous sand dune bedforms fluctuate the distinguishable and dispersive mid-frequency acoustical channel; causing the least distinct arrival patterns in the sand dune area. Numerical simulations using broadband modeling given the adequate initial field and Pade term confirm the observations in the experimental data. This talk also presents experiment results of normal incidence survey tracks, and the errors in reflection coefficient estimation and the resulting sediment properties induced by sand dune bedforms. Results demonstrate that the reflected energy is focused and scattered by different parts of sand dune bedforms, and that they produce significant variation in the estimated reflection coefficients and the inverted geoacoustic properties. [This work was supported by the Taiwan MOST and the US ONR.]
A comparison of finite element and hybrid ray-tracing propagation models for shallow water environments
Authors: Isakson Marcia J. , George Jacob , Harvey David
Published: November 2016

It has been found that the bottom loss can be significantly frequency dependent in shallow water waveguides due to scattering from the rough interface and the volume. This can cause transmission loss to increase with frequency for the same shallow water environment. One way of predicting this frequency dependence is through finite element (FE) propagation modeling which solves the Helmholtz equation exactly within the resolution of the discretization for a completely customizable domain. However, finite element models are difficult to compute for high frequencies and large regions. In this work, two hybrid models are considered and compared with the finite element exact solution. The first model uses a bottom loss calculated using FE for a rough interface as input into a ray based model. The second model uses an even simpler approach by characterizing the bottom loss with the Eckart formulation for use in the ray-based model. The performance of these models as a function of frequency and source and receiver geometry will be assessed. If successful, the simple Eckart formulation could be used to characterize the bottom loss for databases since depends on few parameters. [Work sponsored by the Naval Oceanographic Office and ONR, Ocean Acoustics.]
Ho‘olono i ka Leo o ka Makani (Hear the Voice of the Wind)
Authors: Lopes Keawe , Nogelmeier Puakea , Osorio Jon , Salā Aaran
Published: November 2016

This is a performance of oli, mele, and hula that explores the wide range of chant, song, and dance that Kanaka Maoli have both created and adopted to forge the unique and celebrated music of Hawaii. Scholar/musicians Keawe Lopes, Puakea Nogelmeier, Jon Osorio, and Aaron Sala combine their diverse talents, musical experience and love for the language in this presentation of music, dance, and conversation. Our music is in our nature. Ho‘olono i ka leo o ka makani.
Source level of fin whale calls from the Equatorial Pacific Ocean
Authors: Miksis-Olds Jennifer L.
Published: November 2016

Knowledge of source levels is essential for determining the range of effective fin whale communication and for estimating fin whale density from passive acoustic recordings. Source level calculations were performed on vocalizations automatically detected from spectrograms of Comprehensive Nuclear Test-Ban Treaty Organization data recorded at Wake Island in the Equatorial Pacific Ocean. Received levels were calculated, and transmission loss (TL) was determined using a season- specific OASIS Peregrine parabolic equation model for a 20 Hz signal. The model incorporated the location of the sensor in the deep sound channel, bathymetry of the area, and local sound speed profiles. TL was modeled for 360 bearings with a 1o resolution. TL values between the sensor and source were found for individual vocalizations using ranges and bearings calculated through hyperbolic localization. The exact whale depths were unknown but assumed to be 50 m. Over 7500 localizations of the fin whale 20 Hz call were identified from 2007 to 2009 with an average source level of 184.8 dB + /- 8.6 dB. When the 7500 calls were subsampled at 6 hour intervals to reduce the bias of loud, persistent singers, the average source level was 168.5 dB + /- 4.4 dB (n = 174). [Work supported by ONR.]
Inter-pulse sound field from a marine seismic survey in the Arctic and its potential effects on marine mammal acoustic masking
Authors: Guan Shane , Vignola Joseph F.
Published: November 2016

It has been documented that reverberant fields from marine seismic surveys elevate sound levels, and thus has the potential to mask acoustic signals that are important to marine mammals. In this study, we investigated one-third-octave (OTO) bands of airgun inter-pulse sound fields from a shallow water (<15 m) seismic survey in the Beaufort Sea. The results show that at close distances less than 3 km, peak energy of the OTO band levels were concentrated around 80-110 Hz and the median sound levels were 40-50 dB above ambient. The higher frequency components (>3 kHz) of inter-pulse sound field at these close distances ranged 5-20 dB above ambient. At distances beyond 3 km, the received acoustic energy becomes more uniform up to 1000 Hz. The median OTO band levels at these distances were approximately 10-20 dB above ambient. For higher frequencies, sound levels at these distances were approximately the same as ambient. These results imply that low-frequency bowhead whales could be affected by acoustic masking from seismic airgun inter-pulse sound fields, especially at relatively close distances. However, potential acoustic masking effects to mid-frequency beluga whale echolocation signals are expected to be less profound.
Long range airgun inter-pulse noise field in offshore northern Australian waters
Authors: McPherson Craig , Martin Bruce , Wood Michael , MacGillivray Alexander
Published: November 2016

Elevated ambient noise levels have been shown to affect marine fauna communication. The effects due to increased noise levels from the multipath propagation and reverberation of airgun pulses over large distances is a relatively new area of interest. This research examines a distant seismic survey opportunistically recorded at two locations during a long-term monitoring program in the Timor Sea, Australia. During the analyzed period, the survey was between 168 and 235 km from the Autonomous Multichannel Acoustic Recorders (AMAR). The noise levels between airgun pulses were examined using an incremental computation method based on calculating the root-mean-square sound pressure level in 125 ms sub-intervals. These were compared to ambient noise levels from the month prior to commencement of the seismic survey and during line turns. The received pulse levels and length differences, and therefore inter-pulse noise field, between the recorders were greater than expected given the proportional distance to source difference. The ambient soundscape included biological contributors such as Omura’s whale, fish and benthic crustaceans. Propagation modeling was conducted to examine the effect of the propagation path between source and receiver on the received signals.
Influence of the ocean-bottom structure in the long-distance propagation by seismic survey source
Authors: Tsuchiya Toshio , Gotoh Shinpei , Hirai Yukino , Shimizu Etsuro
Published: November 2016

A source of Multi-Channel Seismic survey system (MCS) is the air-gun array which generates a high level and short pulse sound. However, there was anxiety which has an influence on behavior of a marine mammal by very high acoustic pressure. Therefore, JAMSTEC have decided guidance of regulation along a guideline of NOAA (TTS) in safe purpose of a marine mammal. We'll hope for a MCS investigation by a new JAMSTEC R/V “KAIMEI” (5,500GT) in the Hawaii Islands offing jointly with an U.S. research institute by geological interest in the future. So, long-distance propagation (about 100 km) from air gun source was calculated by a Parabolic Equation simulation for safety ensuring of marine mammals. The simulation results are as follows: 1) When the ocean-bottom of the long-distance transmission path is basalt, for a reflected pulses to pile up from the bottom in various courses, a received pulse width becomes very long. 2) The received level was lower than the TTS level in the watch possible distance from the marine mammal watch room installed in R/V “KAIMEI.” 3) However, when the low restriction level (the behavior obstruction level) was applied for marine mammal protection in the future, we have to lower the air gun transmission level substantially.
Physics-based inversion of multi-beam echo sounder data for seafloor properties
Authors: Jackson Darrell , Hefner Brian T. , Ivakin Anatoliy
Published: November 2016

This is an extension of work on physics-based seafloor inversion for seafloor properties, pioneered by Pouliquen and Lurton and by Sternlicht and De Moustier. This approach fits model time series for backscattered intensity to data, with the best-fit model parameters constituting the inversion output. In the present case, use of multi-beam sonar provides a large number of time series and consequent stronger constraints on model parameters. The method has been tested at two experiment sites, one with sandy and shelly areas and one with a thin layer of mud over sand. Ground truth data were gathered on seafloor roughness using a laser line scanner, on layering using a conductivity probe, on grain-size distribution using diver cores, and on sediment sound-speed and attenuation using acoustic probes. The inversion process involves three stages. First, a sonar-equation model is used to generate echo intensity time series including scattering by both seafloor roughness and volume heterogeneity. Model-data fit provide estimates of acoustic attenuation, volume scattering strength, and interface scattering strength. Next, physics-based models are fitted to the interface and volume scattering strengths, and finally, regression relations are used to provide a set of geoacoustic parameters sufficient to constrain standard reverberation simulations. [Work supported by SERDP.]
Acoustic remote sensing of double-diffusive instabilities and intrusions in ocean frontal zones
Authors: Duda Timothy F. , Lavery Andone C.
Published: November 2016

Small-wavelength sound has been observed to scatter from turbulent microstructure and plankton in the ocean. Additional scattering from salt fingers and diffusive-convective flows that result from double diffusive instabilities (DDI) is also theoretically possible in this same wavelength band, and has been measured in a laboratory setting, though with artificially high gradient parameters. If measurable, small-wavelength backscatter would enable remote sensing of water mass interleaving and mixing from intrusive flows at fronts, which spawn DDI. The factors controlling the visibility of echoes from DDI features is the strength of the features in terms of density and sound-speed anomaly, and the level of masking return from plankton, which may merely interfere or act as passive tracers of these features. Microstructure data collected in double-diffusive instability features are used to compute the expected monostatic backscatter signals. These results suggest that DDI microstructure, from both salt fingering and convection, would be acoustically observable in areas with low to average plankton. The results also suggest that density interfaces (layering structures) associated with DDI would be visible. Acoustic backscatter data show echoes from both the interfaces and DDI microstructure in a frontal zone across a range of wavelengths. [Work supported by the Office of Naval Research.]
Lateral diffraction of underwater sounds between Japan and Chile: experimental results and modeling
Authors: Heaney Kevin D. , Yamada Tomoaki , Zampolli Mario , Haralabus Georgios
Published: November 2016

One hundred shallow underwater explosions on a 300-km profile along an isoline of 500 m sea depth above a slope zone of off the coast of Japan are received at a water-column hydrophone triplet with 2-km intervals in Chile. The over 16,000-km propagations from the northwest to the southeast Pacific Ocean are classified into two groups. One is from the southern explosions. The data show high sound pressure levels and normal travel times. On the other hand, data from the northern ones reveal 6.5 dB lower sound pressure levels and 6.6 s travel time delays on average. Some islands and seamounts in the central Pacific are located on the halfway from the northern explosions. They affect received sound pressure levels and arrival times, but do not block completely, based on the observation. Modeling of this propagation path, using in-plane 2D modeling, shows nearly complete blockage of the sound by the Northern Hawaiian Island chain. Three dimensional parabolic equation modeling shows that this shadow is filled in from diffraction caused by the Midway Islands. Modeling results quantitatively match the measurements for both energy level and travel time.
Giant vesicles as cell models to quantify bio-effects in ultrasound mediated drug delivery
Authors: Pereno Valerio , Carugo Dario , Stride Eleanor P.
Published: November 2016

The biophysical mechanisms that underpin the interaction between microbubbles and cells in the context of ultrasound-mediated drug delivery are still poorly understood. To aid the identification of these mechanisms, giant unilamellar vesicles (GUVs) were used as cell models to quantify changes in membrane properties as a result of the interaction with ultrasound (1 MHz, 150 kPa, and 60 s continuous wave) and phospholipid-shelled microbubbles (DSPC-PEG40S 9:1 molar ratio), either alone or in combination. The spatial quantification of the vesicle lipid order was performed via spectral microscope imaging, by measuring the contours of generalized polarisation (GP) from the emission spectrum of c-Laurdan, a polarity-sensitive dye. Preliminary data show synergistic mechanical and chemical effects on membranes: ultrasound exposure and shear flow alone generally decrease the vesicle lipid packing, while exposures involving microbubbles reveal contrasting effects depending on the initial vesicle composition and acoustic regime. Results from the present mechanistic study provide an insight into the mechanisms of microbubble-membrane interactions, potentially benefitting the design of effective and predictable microbubble-based ultrasound treatments.
Low intensity pulsed ultrasound and lipid-coated microbubbles enhance chondrogenesis of human mesenchymal stem cells in 3D bioprinted scaffolds
Authors: Aliabouzar Mitra , Zhang Lijie G. , Sarkar Kausik
Published: November 2016

Annually, over 6 million people visit hospitals in the United States for issues arising from cartilage damages due to osteoarthritis, acute trauma, rheumatoid arthritis, and sports injury. Articular cartilage is a tissue notoriously hard to regenerate. The objective of this study is to investigate the possibility of facilitating cartilage regeneration using low intensity pulsed ultrasound (LIPUS) stimulation and microbubbles. We have investigated effects of lipid-coated microbubbles (MB) prepared in-house along with LIPUS on proliferation and chondrogenic differentiation of human mesenchymal stem cells (hMSCs) in a novel 3D printed poly(ethylene glycol) diacrylate (PEG-DA) hydrogel scaffold. Our results demonstrate for the first time that LIPUS stimulation in the presence of 0.5% (v/v) MB greatly enhances MSC proliferation for up to 40% after 5 days of treatment. This value is only 18% when excited with LIPUS alone. Furthermore, we optimized acoustic parameters such as excitation intensity, frequency and pulse repetition period for chondrogenic differentiation studies. Synthesis of type II collagen and GAG, which are two key cartilage biomarkers, increased 78% and 17%, respectively, in the presence of LIPUS and MBs, when compared to the controls.
Magnetic targeting of oxygen loaded microbubbles for sonodynamic therapy
Authors: Beguin Estelle , Sheng Jason , Nesbitt Heather , Owen Joshua , McHale Anthony , Callan John , Stride Eleanor P.
Published: November 2016

Previous work has demonstrated that the efficacy of sonodynamic therapy (SDT) can be significantly enhanced by conjugating SDT drugs to oxygen filled microbubbles. For eventual clinical use however, achieving adequate microbubble stability and targeting represents a considerable challenge. This study investigated whether functionalizing microbubbles with magnetic nanoparticles could both improve their longevity and enable localization of the microbubbles to a target site. Phospholipid coated microbubbles containing oxygen and 50 nm spherical magnetite particles were produced by sonication and conjugated to the SDT drug Rose Bengal via an Avidin-Biotin linker. The addition of the nanoparticles was found to substantially enhance the stability of the microbubbles to changes in size and concentration. Orthotopic tumors were induced in BALB/c SCID mice using the BxPc-3 human pancreatic cell line and exposed to ultrasound for 3.5 min (3.5 Wcm-2 at 1 MHz center frequency, 100 Hz pulse repetition frequency, and 30% duty cycle) following intravenous injection of the microbubbles with or without application of a 0.1 T magnetic field. 38 days postimplantation the tumors treated with both ultrasound and the magnet were 50% smaller than the control tumors and exhibited a threefold increase in active caspase as a marker of apoptosis. There was no statistically significant effect of ultrasound alone.
Use of pulse repetition frequency to augment acoustic droplet vaporization in vivo
Authors: Seda Robinson , Harmon Jennifer N. , Fowlkes Jeffrey B. , Bull Joseph
Published: November 2016

infarction shows promise as a treatment. Gas embolotherapy tries to achieve this by locally occluding blood vessels supplying using bubbles resulting from of liquid Sufficient occlusion may be necessary in order to starve to death. The purpose of this study is to increase of in vivo by changing the pulse repetition frequency (PRF) in order to improve the therapy. One milliliter of a solution containing 3 x 107 lipid-coated perfluorocarbon was injected through the tail vein of a rat at a rate of 0.1 mL/min. Acoustic (ADV) was induced in the feeder vessel of the exposed cremaster using a focused, 7.5 MHz and 3 MPa rarefactional A pulse length of 1μs was used, while the PRF was varied from 10 to 1000 Hz. Recordings of ADV showed substantial in both arterial and venous sides at higher PRFs. Vessel rupture and RBC extravasation were also observed. In other instances, blood vessels experienced a narrowing of the lumen at the site of (25% reduction), suggesting an ultrasound/droplet/bubble interaction Bubbles resulting from at high PRF were more likely to occlude small blood vessels, possibly due to
High frame-rate visualization of blood flow with ultrasound contrast agents
Authors: Bruce Matthew , Hannah Alex , Tremblay-Darveau Charles , Burns Peter
Published: November 2016

Recent breakthroughs in diagnostic ultrasound system architectures have enabled new high frame rate (kHz) capabilities, which are opening new opportunities in blood flow imaging. In order to leverage these increases in temporal resolution broader or unfocused beams are employed. The combination high frame and less focused beams with ultrasound contrast agents introduces both new opportunities and trade-offs. One new opportunity is the ability to combine Doppler based processing to visualize both lower velocity blood flow in the microcirculation and higher velocity flow in larger vasculature not possible with conventional techniques. This can be accomplished by combining nonlinear pulsing sequences to separate microbubble and tissue signals with these less focused beams to separate different microbubble flow velocities. The use of less focused beams to image nonlinear echoes from microbubbles distributes ultrasound energy to microbubbles in temporally and spatially different ways. This work explores the compromises of using these less focused beams to visualize moving microbubbles at higher temporal resolutions. The focus will be on the practical challenges of generating nonlinear signals while balancing microbubble disruption and current system reconstruction capabilities. Both in-vitro and in-vivo results will be presented.
High frequency ultrafast flow and strain imaging in the carotid bifurcation: An ex vivo phantom study
Authors: Saris Anne E. , Fekkes Stein , Nillesen Maartje M. , Hansen Hendrik H. , de Korte Chris L.
Published: November 2016

In the Western World, the prevalence of plaques in the carotid is high resulting in stroke and transient ischemic events. Quantification of the plaque size and compositions and the remaining flow and velocity profile is crucial for adequate therapy. We developed a high frequency based method for characterization of plaques and flow. A realistic bifurcation phantom with plaque based on CT scans of a patient was constructed. A realistic pulsatile flow was imposed on the phantom resembling a human flow and pressure profile. Using a Verasonics experimental echomachine with a Visualsonics M250 transducer (Fc = 20MHz), plane wave ultrasound data were acquired at 12.000 fps. A cross-correlation based coarse to fine method was applied on the beamformed data to quantify the axial and lateral strain in the arterial wall and to determine the velocity magnitude and direction of the blood. The strain and flow data were presented side by side for 80 frames covering the full pressure cycle. Strain in the non-diseased carotid wall was moderate with respect to the surrounding tissue. The bifurcation shows large lateral strain due to the force of the pulsating blood. The flow profile shows a turbulent region in the systolic phase at the bifurcation.
Plane-wave imaging of in utero mouse embryo at 18 MHz
Authors: Ketterling Jeffrey A. , Aristizabal Orlando , Phoon Colin K. L. , Yiu Billy Y. S. , Yu Alfred C. H.
Published: November 2016

Plane-wave imaging methods allow for high-speed image capture at a time interval equal to round trip acoustic propagation. Plane-wave imaging is ideally suited for cardiovascular imaging where fine-temporal resolution can reveal important information about cardiac mechanics and blood flow patterns. While plane-wave imaging has been demonstrated in humans for cardiovascular studies, its use in mouse models lags because instrumentation is not yet widely available at appropriate ultrasound frequencies. Thus, the amount of functional information that can be mined from mouse models of cardiovascular disease is limited. Here, an 18-MHz linear-array probe was used to acquire plane-wave data at a frame rate of 10 kHz from an in utero, E14.5 mouse embryo. The probe had 128 elements, 1.5 mm elevation aperture, and 8-mm elevation focus. The mother was placed supine on a heated mouse imaging platform, and then, a series of 2D + time data sequences were captured. The data were beamformed using standard delay-and-sum methods, and then, vector flow estimates were obtained at each pixel location using a least-squares, multi-angle Doppler analysis approach. Although not optimally suited for imaging mouse embryos, the 18-MHz data clearly revealed blood flow patterns in the liver, heart, and umbilical cord.
Treatment envelope of transcranial histoptripsy applied without aberration correction
Authors: Sukovich Jonathan R. , Xu Zhen , Hall Timothy L. , Allen Steven P. , Cain Charles A.
Published: November 2016

Due to the characteristically high absorption, attenuation, and aberrating effects of the skull on ultrasound, transcranial HIFU therapies have typically been restricted to targeting brain regions at depths ≥2cm from the interior surface of the skull. Previous studies using histotripsy, a cavitation based ultrasound therapy relying on short duration (<2 acoustic cycles), high negative pressure amplitude (P ≤ -30MPa) ultrasound pulses to generate cavitation clouds to fractionate tissue, have shown that targeted bubble clouds can be generated through the skull without aberration correction. Here, we present results from experiments probing the minimum depths with respect to the skull surface at which histotripsy applied without aberration correction can generate lesions. Using a 500 kHz, 256-element transducer, histotripsy was applied through an ex vivo human skull to generate lesions in a tissue mimicking phantom embedded within. Lesions were generated at multiple locations within the skull through skull sections with characteristically different geometries. MRI was used to assess lesion generation following treatment. Using histotripsy without aberration correction, we were able to generate lesions at typical depths of between 6 and 12 mm from the interior skull surface. These results demonstrate the potential of histotripsy to target shallower brain regions than current HIFU therapies.
A preliminary in-vivo porcine study of long pulse histotripsy for thrombolysis of intraventricular hemorrhagic clot
Authors: Looi Thomas , Khoklova Vera , Hynynen Kullervo , Drake James
Published: November 2016

Intraventricular hemorrhage is primarily a condition of premature babies where 40% will develop a form of bleeding that occupies >50% of the ventricles in the brain. Due to the fragile nature of patient, there is no treatment except the use of shunts for cerebrospinal fluid accumulation. Long pulse histotripsy (LPH) uses focused ultrasound pulses as a method to non-invasively target and mechanically break up the clot. An in-vivo IVH procine model has been developed and it is used to test the efficacy and safety of using LPH on a Philips Sonalleve. The IVH model has an average clot volume of 3986 mm3 and present in both ventricles. To simulate a neonatal patient, a craniotomy has been performed. The acoustic parameters used are as follows: freq. 1.2 MHz, 2x6 mm focus, 10 ms pulse duration, 10,000 cycles, 1% duty cycle, and acoustic power from 325 to 400 W. Sonication points were placed at the center of the IVH clot. Pre- and post-treatment T1-w, T2-w, and T2*-w MR imaging was completed. Change in the clot volume was measured by segmenting the MR images. The brains were harvested and stained with hematoxylin and eosin for histological examination. Results show that LPH targeted and reduced the clot volume by 28.5-36.7% with a phase change occurring at target. H&E staining showed that visible voids were generated in the clots. Based on early data, it appears that LPH can mechanically reduce the volume of IVH clots. Future work includes increasing the study number and conducting chronic studies to determine the changes to recovery.
A circular microphone array beamformer based on spherical harmonics
Authors: Elko Gary W. , Meyer Jens
Published: November 2016

A circular microphone array that can easily steer its beampattern(s) to any angle in the horizontal plane around the array would be an attractive microphone array for room audio conferencing. An elegant solution to this problem to design a modal beamformer based on circular harmonics. However, a modal beamformer based on circular harmonics suffers from the loss of control of the beampattern out of the plane of the array. We will present a modified modal beamformer for the circular array that is based on spherical harmonics. This approach allows full control of the beampattern and maintains the efficient steerability known from modal beamformers. Measurements of a specific implementation with 16 sensors will be presented.
Piezoelectric low frequency shear horizontal guided wave transduction
Authors: Boivin Guillaume , Tremblay Nicolas , Zednik Ricardo , Belanger Pierre
Published: November 2016

Ultrasonic guided waves are now routinely used in non-destructive evaluation. In plate-like structures, three fundamental modes can propagate, namely, A0, S0, and SH0. Most of the guided wave literature has thus far focused on the use of A0 and/or S0 because these modes are easy to generate in plate-like structures using standard piezoceramic transducers. Yet, at low frequency, A0 and S0 are dispersive. The consequence of dispersion is that signal processing becomes complex for long propagation distances. SH0, on the other hand, has the particularity of being the only non-dispersive guided wave mode. Omnidirectional transduction of SH0 requires a torsional surface stress which cannot be easily generated using standard piezoceramic transducers. This paper compares a transducer concept based on piezoceramic patches assembled to form a discretized circle and a second concept based on a tellurium dioxide disk. The external diameter of the transducers was chosen to be half the SH0 wavelength at 100 kHz in an aluminium plate. Finite element simulations using the Comsol Multiphysics environment showed that in a 1.6 mm aluminium plate the modal selectivity as well as the omnidirectionality of the tellurium dioxide concept was superior at 100 kHz.
Thermal saturation and its suppression in high-power, compact carbon nanotube thin-film thermophones
Authors: Brungart Timothy A. , Chatterley James J. , Beck Benjamin S. , Kline Brian L. , Yoas Zachary W.
Published: November 2016

Carbon nanotube (CNT) thin-film thermophones, at sufficiently high input power levels, suffer from thermal saturation where an increase in the input power does not result in a corresponding increase in the sound pressure level generated. It is believed that high temperature air, trapped in and around the CNT film, inhibits the ability of the CNT film to cool sufficiently between heating cycles, thus limiting the sound pressure output and increasing in severity with both input power and frequency. Thermal saturation appears to be particularly acute for CNT thermophones designed for compactness or when placed inside a protective or loudspeaker enclosure, where natural convection or heat transfer from the film is inhibited. Fan cooling was integrated into a CNT thermophone and demonstrated to both reduce the temperature of the CNT film and suppress, almost entirely, the effects of thermal saturation.
Accurate time-domain modeling of the bowed string
Authors: Mansour Hossein , Woodhouse Jim , Scavone Gary
Published: November 2016

An enhanced time-domain, travelling-wave model of the bowed string is presented. The model includes several new features: realistic damping verified by experimental data, detailed coupling of body modes (derived from experimental data) in both polarizations of string motion, coupling to transverse and longitudinal bow-hair motion, and coupling to vibration of the bow stick. The model is designed to allow the various features to be turned on or off, such that their influence on the results can be assessed independently. Schelleng diagrams are computed using different configurations and are compared based on different metrics to reveal trends of behavior.
Unsupervised grammar induction from music data
Authors: Yoshii Kazuyoshi
Published: November 2016

Music has a lot of similarities to language. Since most languages have clear syntactic structures (e.g., words should be arranged in the SVO order), many linguists have proposed various kinds of grammar theories by carefully and manually investigating language data. The situation is the same with Western music. Although a single musical note (cf. alphabet) has no meaning by itself, a cluster or pattern of multiple musical notes over the quantized time-frequency grid (cf. word) can invoke some impression and such short patterns are concatenated or superimposed (unique to music) to produce more complicated meaning (cf. sentence). We introduce several attempts to discover latent structures underlying music from acoustic or symbolic data (music signals and musical scores) in an unsupervised manner. Integrating statistical acoustic and language models as in speech recognition, for example, it is possible not only to transcribe music but also to discover that particular note combinations can form chords. A key feature of this approach is that both models are trained jointly only from acoustic data. Recently, we have attempted to induce music grammars from polyphonic scores by leveraging the state-of-the-art techniques of natural language processing. This would contribute to automatic music transcription and computational musicology.
Amphitheaters: The noise within
Authors: Talaske Richard H.
Published: November 2016

The continuing success of outdoor performance facilities demonstrates that music and theatre can be enjoyed within environments which are much nosier than the silent indoor concert halls and theaters we know and love. However, there are limits to how much noise is acceptable. Design methods can be implemented to control the noise and significantly improve the listening experience. This presentation offers insight into the design of outdoor music venues and the management of noise as heard by the patron and performers. Numerous amphitheaters will be discussed, including the Jay Pritzker Pavilion, American Players Theatre, and Aurora’s River’s Edge, thereby offering examples of facilities designed for symphonic music, theatre, and popular music. The importance of acoustic considerations such as signal-to-noise, frequency response, and direction of arrival of sound will be discussed.
Next generation soundscape design using virtual reality technologies
Authors: Chung Andy , To Wai M. , Schulte-Fortkamp Brigitte
Published: November 2016

Sound quality has been demanded by the community as part of the smart city initiatives to enjoy a real liveable environment. While a lot of governments pay attention to environmental issues such as air quality and waste, those who care about the sonic environment still rely primarily quantitative levels for either compliance or improvement. Sound quality is most likely ignored. There is at present the international standard ISO 12913-1:2014 providing the definition and the conceptual framework of soundscape. Despite the situation, sound quality is a subjective matter after all and relies very much on human perceptions, as well as the contextual environment. Sound walk, questionnaire, and lab test are common tools used in soundscape studies. These tools allow a good understanding of the perception of the prevailing sonic environment. To figure the sound quality of different design options, though, we can immerse the participants in a virtual, but photorealistic environment, so that they can perceive, compare, and give feedback as if they were in the real environment. A mobile VR application has been developed for iterating soundscape design and fine-tuning. This paper presents this application with case studies.
Real-time natural soundscape generation based on current weather conditions for workspace voice-masking
Authors: Riggs Caitlin , Braasch Jonas
Published: November 2016

Sound masking in work spaces has been implemented to decrease likelihood of distraction from work tasks and improve speech privacy. Current uses of noise as maskers commonly apply broadband white or pink noise signals due to their perceived neutrality. This research combines work into the restorative properties of exposure to nature/natural sounds and pilot studies of natural sounds as maskers to suggest a noise-masking system of “natural” sounds. This system composes a natural soundscape in real time determined by the current weather and time of day such that the masking audio is aesthetically pleasing and informative about the outside world in addition to providing improved speech privacy and reducing distraction when compared to a setting with no masking system. Currently, there is no experimental foundation to suggest that restoration or slowed attentional fatigue can occur if this type of alternative masking sound is presented during a task. This implementation of a dynamic, immersive soundscape masker begins the investigation into the practical efficacy of such a masking system.
Visualization movie analysis of acoustic phenomena of a supersonic jet and Its comparison with intensity vectors
Authors: Akamine Masahito , Okamoto Koji , Gee Kent L. , Neilsen Tracianne B. , Teramoto Susumu , Okunuki Takeo , Tsutsumi Seiji
Published: November 2016

The authors have studied the acoustic wave from an unheated, Mach 1.8 ideally expanded jet by using the acoustic intensity vector measurement and analysis of high-speed schlieren visualization movies (for example, the Fourier transform and wavelet-based conditional sampling). Both these techniques reveal the characteristics of the acoustic wave, such as the propagation direction and location of a source region. These techniques have their own advantages: the quantitative data can be obtained by using the acoustic intensity vector measurement, whereas the acoustic field including a close region to the jet can be visualized with high spatial resolution by using the Schlieren movie analysis. Therefore, their comparison is a meaningful approach to understand the acoustic phenomenon. This presentation compares these two techniques and describes what can be discussed with their comparison, considering the advantage and disadvantage of each measurement technique.
Results of scale model acoustic tests using supersonic cold jets for H3 launch vehicle
Authors: Sarae Wataru , Sawada Atsushi , Terashima Keita , Haga Takanori , Tsutsumi Seiji , Ishii Tatsuya , Hiraiwa Tetsuo
Published: November 2016

Acoustic test using Mach 2 cold jet was conducted for the H3 launch vehicle currently being developed in Japan. Effect of the clustered engines and the newly built movable launcher on the lift-off acoustics was investigated. The overall acoustic level taken by the farfield microphones did not show proportional increase in the number of engines, especially for the angles corresponding to the Mach wave radiation from the free jets. The observation here disagrees with the empirical prediction model. The computational fluid dynamics was also employed to analyze the acoustic mechanism of clustered engines.
Intensity-based laboratory-scale jet noise source characterization using the phase and amplitude gradient estimator method
Authors: Gee Kent L. , Neilsen Tracianne B. , Whiting Eric B. , Torrie Darren K. , Akamine Masahito , Okamoto Koji , Teramoto Susumu , Tsutsumi Seiji
Published: November 2016

A new method for the calculation of vector acoustic intensity from pressure microphone measurements has been applied to the aeroacoustic source characterization of an unheated, Mach 1.8 laboratory-scale jet. Because of the ability to unwrap the phase of the transfer functions between microphone pairs in the measurement of a broadband source, physically meaningful near-field intensity vectors are calculated up to the maximum analysis frequency of 32 kHz. This result improves upon the bandwidth of the traditional cross-spectral intensity calculation method by nearly an order of magnitude. The new intensity method is used to obtain a detailed description of the sound energy flow near the jet. The resulting intensity vectors have been used in a ray-tracing technique to identify the dominant source region over a broad range of frequencies. Additional aeroacoustics analyses provide insight into the frequency-dependent characteristics of jet noise radiation, including the nature of the hydrodynamic field and the sharp transition between the Mach wave and sideline radiation.
Far-field acoustical measurements during QM-2 solid rocket motor static firing
Authors: Reichman Brent O. , Neilsen Tracianne B. , Ohm Won-Suk , Harker Blaine M.
Published: November 2016

The five-segment Space Launch System solid rocket motor was recently tested at Orbital ATK. Far-field acoustical measurements were performed at angles between 80° and 120° relative to the rocket exhaust at a distance of roughly 2500 m from the rocket, approximately 800 nozzle diameters. The angular aperture allows for evaluating spatial variation in acoustic properties and a comparison with similar tests in the past, including the 2015 test of the same rocket motor. Although terrain variations introduce uncertainty, an approximate 10 dB change in level is seen throughout the aperture, consistent with previous studies. In addition, at low frequencies a high degree of correlation is seen. Near the peak radiation direction high levels of derivative skewness indicate significant shock content and crackle. This dataset also presents the opportunity to test a new method for processing acoustic vector intensity [Thomas et al., JASA 137, 3366-3376 (2015)]. Comparison with the traditional method shows an increase in usable bandwidth of more than an order of magnitude.
Electrophysiological correlates of auditory object binding with application to autism spectrum disorders
Authors: Bharadwaj Hari M. , Khan Sheraz , Hämäläinen Matti , Kenet Tal
Published: November 2016

A fundamental problem in auditory neuroscience is to understand how the fragmented physiological representation of sound along the auditory pathway leads to unified percepts of broadband objects and streams. Natural sounds from a single physical source often exhibit strong temporal coherence between their acoustic components. We know from previous psychoacoustic studies that this temporal coherence is a cue for perceptual binding. Using magnetoencephalography (MEG), we measured neural responses to (1) a mixture of modulated tones, and (2) sentences of four-tone sine-wave speech, as we parametrically varied the temporal coherence between their components. We found that in parallel with behavior, MEG responses from the primary auditory cortex varied in with the temporal coherence of the stimulus. Further, cortical oscillatory signatures from the same region also varied with the stimulus coherence. These results suggests that signatures of temporal-coherence-mediated binding are already present at the level of the auditory cortex and may be mediated in-part by oscillatory thalamocortical processes. Finally, when we measured MEG responses in a cohort of children with autism spectrum disorders, we found a reduction in both the evoked responses and the oscillatory activity suggesting anomalous early cortical processing of complex sounds.
Switching of auditory attention
Authors: Lee Adrian K. C. , McLaughlin Susan A. , Larson Eric
Published: November 2016

Active listening in an acoustically crowded environment requires both maintaining and switching attention between auditory objects. General behavioral costs associated with task-switching are well documented in the cognitive literature. Yet there are many unanswered questions about the cost associated with switching between auditory objects relative to the type of feature-based attention employed. For example, do listeners use the same strategy to switch attention between locations as would be used to switch attention between speakers with different pitches? Is it equally difficult to switch attention within the same feature (e.g., attending to the left then the right talker) compared to switching across features (e.g., attending to the left talker then the one with the higher pitch)? Are the neural substrates recruited differentially depending on whether a listener is attending to spatial or non-spatial features of the auditory stimuli? In this talk, evidence from human psychophysical and physiological studies will be presented suggesting that auditory attention switching is not a monolithic construct. The interaction between top-down attention and different degrees of auditory stream degradation will also be discussed.