bluuebunny/crossref_metadata_2025 huggingface dataset:
Addressing nonlinear propagation effects in characterization of high intensity focused ultrasound fields and prediction of thermal and mechanical bioeffects in tissue
Authors: Khokhlova Vera A. , Yuldashev Petr V. , Kreider Wayne , Sapozhnikov Oleg A. , Bailey Michael R. , Khokhlova Tatiana D. , Maxwell Adam D. , Crum Lawrence A.
Published: November 2013

Nonlinear propagation effects are present in most fields generated by high intensity focused ultrasound (HIFU) sources. In some newer HIFU applications, these effects are strong enough to result in the formation of high amplitude shocks that actually determine the therapy and provide a means for imaging. However, there is no standard approach yet accepted to address these effects. Here, a set of combined measurement and modeling methods to characterize nonlinear HIFU fields in water and predict acoustic pressures in tissue is presented. A characterization method includes linear acoustic holography measurements to set a boundary condition to the model and nonlinear acoustic simulations in water for increasing pressure levels at the source. A derating method to determine nonlinear focal fields with shocks in situ is based on the scaling of the source pressure for data obtained in water to compensate for attenuation losses in tissue. The accuracy of the methods is verified by comparing the results with hydrophone and time-to-boil measurements. Major effects associated with the formation of shocks are overviewed. A set of metrics for determining thermal and mechanical bioeffects is introduced and application of the proposed tools to strongly nonlinear HIFU applications is discussed. [Work supported by NIH EB007643, T32 DK007779, and RFBR 13-02-00183.]
Holography and numerical projection methods for characterizing the three-dimensional acoustic fields of arrays in continuous-wave and transient regimes
Authors: Kreider Wayne , Maxwell Adam D. , Yuldashev Petr V. , Cunitz Bryan W. , Dunmire Barbrina , Sapozhnikov Oleg A. , Khokhlova Vera A.
Published: November 2013

The use of projection methods is increasingly accepted as a standard way of characterizing the 3D fields generated by medical ultrasound sources. When combined with hydrophone measurements of pressure amplitude and phase over a surface transverse to the wave propagation, numerical projection can be used to reconstruct 3D fields that account for operational details and imperfections of the source. Here, we use holography measurements to characterize the fields generated by two array transducers with different geometries and modes of operation. First, a seven-element, high-power therapy transducer is characterized in the continuous-wave regime using holography measurements and nonlinear forward-projection calculations. Second, a C5-2 imaging probe (Philips Healthcare) with 128 elements is characterized in the transient regime using holography measurements and linear projection calculations. Results from the numerical projections for both sources are compared with independent hydrophone measurements of select waveforms, including shocked focal waveforms for the therapy transducer. Accurate 3D field representations have been confirmed, though a notable sensitivity to hydrophone calibrations is revealed. Uncertainties associated with this approach are discussed toward the development of holography measurements combined with numerical projections as a standard metrological tool. [Work supported by NIH EB007643, P01DK043881, R01DK092197 and T32DK007779, NSBRI through NASA NCC 9-58, and RFBR 13-02-00183.]
Feasibility of using infra-red system for absolute calibration of high intensity focused ultrasound fields
Authors: Shmeleva Svetlana , Khokhlova Vera , Gavrilov Leonid , Martin Eleanor , Sadhoo Neelaksh , Shaw Adam
Published: November 2013

In recent years, considerable progress has been achieved in the use of infrared (IR) method for measuring acoustic fields of high intensity focused ultrasound (HIFU) transducers. The principle of the method is to determine the intensity distribution at the surface of an acoustic absorber by measuring the distribution of the initial rate of temperature increase at the start of insonation. Here, the method is extended to estimate the absolute values of intensity in ultrasound fields of HIFU transducers. The approach compares the temperature rise measured at the surface of a thin absorber using an IR camera and the pressure distribution measured in water using a hydrophone. The measurements were carried out for two focused HIFU transducers and a flat physiotherapy transducer. During the IR measurement, the transducer was driven in tone burst mode to avoid interference from reflected acoustic waves between the absorber/air interface and the transducer. The method enables fast quantitative estimations of intensity distributions that agree well with hydrophone measurements and gives reasonably consistent results for medical transducers of different geometries. [Work was supported in parts by RFBR 12-02-31388, 12-02-00028, 13-02-00183; NIH 2R01EB007643-05, the European Metrology Research Programme (Joint Research Project HLT03) and the UK National Measurement Office.]
Sensitivity and power handling capacity of the Ultrasound Imparted Air-recoil Resonance method for acoustic power estimation
Authors: Kaiplavil Sreekumar
Published: November 2013

Recently, we have introduced a novel method, the Ultrasound Imparted Air-recoil Resonance (UIAR), for the estimation of acoustic power with high sensitivity. Salient features of this approach over existing practices include fast response, electrical and magnetic inertness and hence MRI compatibility, portability, high damage threshold, and immunity to vibration and interferences, low cost, etc. The angle of incidence should be fixed for accurate measurement. However, the transducer-detector pair can be aligned in any direction with respect to the force of gravity. In this sense, the operation of the device is orientation-independent. The device is useful in the case of pulsed/burst as well as continuous ultrasound exposure. Sensitivity was found to be extendable down to the micro Watt range or even below that, however, critical issues related to the thermo-viscous loss mechanisms in the system need careful optimization. The power handling capacity is a few hundreds of Watts, which could be augmented using suitable materials for the Helmholtz resonator window that functions as the acoustic filed sensing head. A detailed account of the sensitivity and high-power estimation capability of the UIAR technique will be presented in the paper.
Algebraic reconstruction technique considering curved ray for sound-speed tomography with ring-array transducer
Authors: Nakamura Hirofumi , Kanagawa Tetsuya , Tamano Satoshi , Azuma Takashi , Yoshinaka Kiyoshi , Sasaki Akira , Takagi Shu , Matsumoto Yoichiro
Published: November 2013

Our objective is to develop an ultrasound treatment and diagnosis integrated system for breast cancer. Ultrasound computed tomography (UCT) in imaging and high intensity focused ultrasound (HIFU) in therapy was integrated to achieve ideal treatment system. Profiles of sound speed and attenuation obtained by UCT has informative parameters to correct deformation of HIFU beam. We try to develop an imaging system using ring-array transducer with 1024-elements, multiplexer connecting 1024 to 256 and Verasonics programmable imaging system with 256 channels. First, an iterative Simultaneous Algebraic Reconstruction Technique (SART) reconstruction methods with an assumption of straight path was employed. SART was applied to projection data calculated by a FEM simulator treating actual curved ray caused by tissue inhomogeneity. In these results, estimated error in sound speed difference was 53%. Then we introduced Linear Travel-time Interpolation (LTI) to SART to implement effects of curved ray. LTI is a ray tracing method based on Fermat’s Principle. We evaluated the LTI and SART integrated method for sound-speed tomography. Travel-time for reconstruction was achieved from simulation based on finite difference method. The reconstruction image was highly corresponded with original image. Reconstructed image from experimental projection data will be reported in the presentation.
Low-power electricity generation from dynamical systems
Authors: Erturk Alper
Published: November 2013

This talk will review our research on energy harvesting from electroelastic dynamical systems for low-power electricity generation with an emphasis on piezoelectric transduction. The transformation of vibrations into electricity using piezoelectric materials with the goal of powering small electronic components has received growing attention over the last decade. Enabling energy-autonomous small electronic components can lead to reduced maintenance costs in various wireless applications, such as structural health monitoring of civil and military systems. After a brief discussion of energy harvesting methods for low-power electricity generation, this talk will be focused on linear and nonlinear energy harvesting using piezoelectric materials through the topics of distributed-parameter electroelastic dynamics of energy harvesters, performance and frequency bandwidth enhancement by exploiting nonlinear dynamic phenomena, deterministic and stochastic excitation of monostable and bistable configurations, effects of dissipative and inherent electroelastic nonlinearities, electroaeroelastic flow energy harvesting using airfoil-based and bluff body-based configurations, and enhanced harvesting of structure-borne propagating waves using elastoacoustic mirrors and metamaterial structures. A brief introduction to our efforts on multifunctional underwater thrust and power generation using flexible piezoelectric composites will also be given.
Coupling efficiency analysis of hydraulic pressure energy harvesters
Authors: Skow Ellen , Cunefare Kenneth , Erturk Alper
Published: November 2013

The acoustic pressure within hydraulic systems, referred to as pressure ripple, is a high intensity energy source that can be utilized for powering sensor networks. A section of such a system can be modeled as a one dimensional waveguide, where the intensity can reach up to 1000 mW/cm2 from a 300 kPa pressure ripple (peak-to-peak acoustic pressure) within a hydraulic system. Hydraulic pressure energy harvesters (HPEH) are devices designed to convert the pressure ripple into electrical energy, thereby enabling wireless sensor nodes. HPEH couple the dynamic fluid pressure to a piezoelectric stack, which is connected to a harvester circuit to optimize power output. A key aspect of the HPEH design is the fluid-mechanical coupling of the pressure ripple to the stack for maximizing the energy extracted. The efficiency of HPEH device and harvester circuit potential power output can be determined using the volume velocity of the pressure ripple, the coupling efficiency of the HPEH, and the conversion efficiency of the piezoelectric stack. In this work, the coupling efficiency and the power output efficiency of currently developed HPEH devices will be analyzed and compared to modeled efficiency of such devices.
Teponaztli, an ancient percussion instrument
Authors: Beristain Sergio
Published: November 2013

Ancient percussion instruments in Mesoamerica included the Huehuetl and the Teponaztli, both made out of a single piece of hollow trees, which pretty often were decorated with low profile representations of animals, warriors or other ceremonial symbols, both were often used by the Aztecs and Tarascas among many other cultures in the region. The first one is normally used in a vertical position and has an strained animal skin, typically an ocelot, in the top side in order to excite it with wooden sticks or by the bare hands, while the second is formed by a couple of tongues made out from the same tree cortex, and excited by a couple of wooden sticks covered with hard rubber. In both the hollowed tree forms a resonant chamber in order to increase the sound level, and include openings in order to allow the exit of the sound from inside of the drum. They were employed for ceremonies, festivities and communication. Here, there are presented the sound characteristics of a small “teponaztli,” which is actually a small copy scaled about 5:1 of a real one, which can usually only be seen in archaeological museums.
Using simplified terrain and weather mapping in outdoor sound propagation predictions
Authors: Coyle Whitney , Sparrow Victor , Ikelheimer Bruce
Published: November 2013

A complementary experimental and computational study was undertaken to assess the variability due to model sensitivities when predicting propagation in realistic outdoor environments by using a Green’s Function Parabolic Equation (GFPE) method and including realistic weather and terrain profiles. In order to test the validity of the basic and enhanced model including real terrain and weather data, field measurements were conducted at Hogan’s Mountain, North Carolina. By incorporating USGS terrain and measured weather profiles, this project further developed a Hogan’s Mountain specific GFPE to include a stair-step terrain mapping capability and linearly interpolated sound speed profiles. This Hogan’s Mountain GFPE uses matching conditions for comparison to the measured received levels from the field test data. Due to the vast data set acquired, which allows for comparison of the model to measurement in a multitude of propagation situations, several comments are made regarding the choice of calculation parameters as well as the validity of the basic and altered Hogan’s Mountain GFPE for different propagation prediction settings. Sample results will illustrate the agreement based on frequency, specific terrain and weather measured along the propagation path for individual source-receiver pairs of interest. [Work supported by Spawar Systems Center Pacific.]
Mapping the extent of noise on a national scale using geospatial models
Authors: Mennitt Dan , Fristrup Kurt , Nelson Lisa , McKenna Megan
Published: November 2013

Because many wildlife habitats, geological processes, and anthropogenic impacts occur on a regional scale, acoustical analyses must encompass a similar extent. Geospatial sound modeling incorporates spatial representations of biological, geophysical, climatic, and anthropogenic factors to assess expected contributions to the existing sound pressure level from both anthropogenic and natural sources. This method enables mapping of sound pressure levels at national scales. The models do not directly apply the physics of sound propagation or characteristics of individual sound sources. Instead, long-term sound pressure level measurements from hundreds of sites across the contiguous United States were used to train regression models to predict acoustic conditions. This talk will focus on the implications of the resulting acoustic maps of the contiguous United States. In addition, noise and the relationship to light pollution will be considered.
Infrasonic wind noise in a pine forest
Authors: Raspet Richard , Webster Jeremy , Abbott JohnPaul
Published: November 2013

Comparison of the ambient infrasonic noise levels at 39 stations of the International Monitoring System indicated that wind noise levels are as much as 6 dB quieter at heavily vegetated stations. This combined experimental and theoretical study investigates mechanisms for wind noise generation in and above a uniform pine forest (h ~7.0 m). A 10 m tower instrumented with ultrasonic anemometers measures the turbulence field and wind velocity profile above and below the canopy and an infrasonic transducer is collocated on the ground. A prediction of the turbulence-shear wind noise contribution from the turbulence above the canopy and also from the turbulence within the canopy are calculated and compared to the data. The above canopy contribution agrees well with the data for the low frequency regime (<0.5Hz). Surprisingly, this contribution is larger than would occur over a grassy plane with similar meteorological conditions. The under canopy turbulence-shear interaction calculation underpredicts the small high frequency contribution, however an estimate of the turbulence-turbulence interaction wind noise in the under canopy layer provides a good fit to this data. [Work supported by the U. S. Army Research Laboratory and the U. S. Army Research Office under grant W911NF-12-1-0547.]
Experimental investigation of large porous wind fences for infrasonic wind noise reduction
Authors: Abbott JohnPaul R. , Raspet Richard , Webster Jeremy
Published: November 2013

An extensive experimental investigation of large porous wind fences constructed from commercially available materials has recently been completed. Measured changes to the wind noise, turbulence, and wind velocity profile inside the fence resulting from varying the fence’s height, diameter, and porosity have been measured. The effect of other variables, including porous roofs, a bottom gap, and the addition of secondary windscreens were also studied. An empirical model based on measurements of the turbulence correlation length around the outside of the fence and the velocity gradient across the fence's surface has been derived to develop a better understanding of the wind noise reduction mechanisms. The measurements and model are then used to suggest an optimized wind fence design and predict the band width and magnitude of the wind noise reduction curve.
Floor vibration testing in hospital operating rooms
Authors: Nash Anthony
Published: November 2013

Operating rooms in several hospitals have been studied for their in-situ floor vibration properties. The motivations ranged from identifying the cause of unstable images observed in a surgical microscope to determining whether a portion of a long span floor in a hospital parking garage could be adapted for a future surgical center. As part of these studies, several types of floor excitation techniques were employed including a vibration exciter, a “heeldrop,” and a human walker. The input magnitudes from the first two of these excitation sources can be measured at a given location using a calibrated force plate. The human walker, however, is a “wild card” source since the location of the footfall is constantly changing; moreover, the nature of the applied force pulse is unknown under field conditions. Thus, one cannot easily quantify the dynamic force of the test signal that is most germane to the assessment of floor vibration in the field. The paper will review the literature governing floor vibration limits in sensitive buildings and summarize the utility of information obtained by various floor testing protocols.
Simulations of sound change resulting from a production-recovery loop
Authors: Parrell Benjamin , Lammert Adam , Narayanan Shrikanth , Goldstein Louis
Published: November 2013

We present a computational model of lenition-based sound change. Speech production targets for constriction degree are modeled by differential equations with a single stable fixed point at the target constriction degree that interact with higher order equations that reflect prosodically conditioned variation. This output is then input to the articulatory-to-acoustic forward map, the quantal nature of which causes continuous variation in constriction degree to result in two outcomes: closure or spirantization. The quantized acoustic outcomes are then used as the input for the language learner, who must recover the produced constriction degree in the ambient language environment to produce the speech unit appropriately. We model this recovery as estimating the parameters of an articulatory distribution that is most likely to have produced the acoustic observations (i.e., the maximum likelihood estimate). In particular, we optimize the parameters of a Gaussian distribution with respect to their log-likelihood function, given the acoustic data that results from applying the quantal forward map to that distribution. We show how this production-recovery loop may lead to sound change in a language by varying the nature of the articulatory-to-acoustic map as well as the amount of knowledge the learner has about both the prosodic structure and articulatory-to-acoustic map.
Coarticulation as an epiphenomenon of syllable-synchronized target approximation—Evidence from fundamental frequency aligned formant trajectories in Mandarin
Authors: Gao Hong , Xu Yi
Published: November 2013

An experiment was carried out to test the hypothesis that the syllable is a time structure that synchronizes tonal, consonantal, and vocalic target approximation movements. The strategy was to align formant movements with F0 turning points of lexical tones as time reference, and then assess the temporal scope of articulatory movements by comparing formant trajectories and their turning points across minimal pairs. Native Mandarin speakers produced C1V1#C2V2 disyllabic sequences where C2 is /y/, /w/ or /l/, and V1 and V2 varied in height and frontness. Analysis of F0-aligned F2-3 (average of F2 and F3) trajectories revealed patterns in support of the main hypothesis. First, movements clearly discernable as approaching either C2 or V2 targets started at about the same time from the center of V1, i.e., well before the conventional landmark-based syllable boundary. Second, some F2-3 trajectories extended continuously from the center of V1 to the center of V2, across the intervening /l/, indicating a long and uninterrupted V2 approximation movement. These results provide support for the view that genuine CV co-production occurs only between onset C and the following V, while the rest of the “coarticulation” is only an epiphenomenon (arising from landmark-based segmentation) of syllable-synchronized target approximation.
Modeling imaging performance of multistatic acoustic arrays of non-uniform geometries
Authors: Lee Michael , Liebling Michael , Lee Hua
Published: November 2013

Unlike the most arrays in acoustical imaging systems, a system based on a dynamically reconfigurable multistatic array would be able to physically adapt to the volume of interest, improving angular coverage of the illuminating array aperture and thus resolution of target images. With such arbitrary distributions of array elements, the extent to which each element contributes to the image reconstruction of targets may change with each imaging cycle. For this reason, the acoustic beamspread and direction of each array element become dominant variables in the resolving capability and data processing of the system. In this paper, non-linear element distributions with specified beamspreads are simulated to image point targets for the purpose of analyzing this relationship and its relevance to spatial bandwidth. MATLAB simulations based on coherent illumination and image reconstruction provide the foundation for this work. By adding the capability to specify beamspread angles and direction for each element, imaging simulation results have more practical value. For any given array configuration, the region of interest can now be visualized in terms of favorability for acoustic illumination. Likewise, the beamspread specifications enable the image reconstruction algorithm to more reliably reconstruct targets.
Growth in acoustics consulting at Bolt, Beranek and Newman with Ron and Warren
Authors: Rosenberg Carl , Cavanuagh William J. , Wood Eric
Published: November 2013

Acoustics consulting was a growing field in technology support to the architectural world in the second half of the 20th century, spearheaded by Bolt Beranek and Newman and other new firms. As part of this growth, BBN embarked on a program of establishing branch offices around the country. Ron McKay and Warren Blazier were outstanding technical leaders in their respective fields and also vanguards of these developments, although both found fulfillment later in their careers away from BBN. This paper shares the growth and evolution of the profession through these two paragons of consulting leadership, and acknowledges the profound contributions of their early years to the reputation of the acoustics consulting world.
Tethys: A workbench for bioacoustic measurements and environmental data
Authors: Roch Marie A. , Baumann-Pickering Simone , Hwang Daniel , Batchelor Heidi , Berchok Catherine L. , Cholewiak Danielle , Hildebrand John A. , Munger Lisa M. , Oleson Erin M. , Rankin Shannon , Risch Denise , Širović Ana , Soldevilla Melissa S. , Van Parijs Sofie M.
Published: November 2013

A growing number of passive acoustic monitoring systems have resulted in a wealth of annotation information, or metadata, for recordings. These metadata are semi-structured. Some parameters are essentially mandatory (e.g., time of detection and what was detected) while others are highly dependent upon the question that a researcher is asking. Tethys is a metadata system for spatial-temporal acoustic data that provides structure where it is appropriate and flexibility where it is needed. Networked metadata are stored in an extended markup language (XML) database, and served to workstations over a network. The ability to export summary data to OBIS-SEAMAP is in development. The second purpose of Tethys is to serve as a scientific workbench. Interfaces are provided to networked databases, permitting the import of data from a wide variety of sources, such as lunar illumination or sea ice coverage. Interfaces currently exist for Matlab, Java, and Python. Writing data driven queries using a single interface enables quick data gathering from multivariate sources to address hypotheses. Examples showing the results of analysis of acoustic data from acoustic deployment from 26 sites across the Northern Pacific will be shown.
Determining the contribution of cetacean noise to the marine soundscape of Australia’s Northwest Shelf
Authors: Erbe Christine
Published: November 2013

The continental shelf off Western Australia is 500 km wide and has an annual mean sea surface temperature of 28 degrees Celsius. Biodiversity is rich and includes at least 45 cetacean species (whales and dolphins). A catalog of sounds produced by these animals was established based on a literature review and recordings obtained by the Centre for Marine Science and Technology at Curtin University. An automatic detector for these sounds was developed and includes the following steps: (1) Fourier transformation of the recorded time series, (2) spectrogram normalization, (3) computation of information entropy of the spectrogram, (4) investigation of entropy distribution and thresholding, and (5) removal of detections with fewer than a predefined number of spectrogram pixels. Detector performance was assessed by comparison to manual detections. The total energy of the biological sounds detected was computed to determine the contribution of cetaceans to the underwater noise budget at several locations and times of year. [Work supported by Chevron Australia.]
Ultrasound-mediated remote actuation of implantable devices for localized drug delivery
Authors: Chitnis Parag V. , Ordeig Olga , Sia Samuel K.
Published: November 2013

Direct local delivery of therapeutics can significantly improve long-term outcome and quality of life for cancer patients. We present a drug-delivery approach that employs focused ultrasound (FUS) for remotely actuating drug-loaded, biocompatible implants consisting of porous NiPAAm hydrogels encapsulated in a PDMS disk. The hydrogels were 1 mm thick and 6 mm in diameter. The NiPAAm formulation was designed to contract to 30% of original size when heated to 45°C. The capsule was loaded with 20-kDa TRITC-Dextran and placed in a custom-designed PDMS chamber containing de-ionized water. A thermocouple was embedded in the NiPAAm gel to monitor local temperature. TRTIC-dextran released to the surrounding media was quantified by absorbance at 540/580 nm. Maintaining the capsules at 37°C for two days using a hot plate did not trigger release. A 1.5-MHz FUS transducer operating at low intensities (<500 W/cm2) elevated the gel temperature to 45°C in 32.6 ± 19 s (N = 10). Thermocouple was employed as a feedback to modulate (on/off) FUS in real-time to maintain gels at 45°C for 10~min, which resulted in a release of 10.6 ± 0.3~μg of dextran. Capsules were then implanted in eight mice; four mice were subjected to FUS. FUS actuated release in vivo as evidenced by fluorescence imaging.
Delivery of different-size molecules by ultrasound-induced blood-brain barrier opening and its correlation with acoustic emission
Authors: Chen Hong , Srivastava Anushree , Sun Tao , Olumolade Oluyemi , Konofagou Elisa E.
Published: November 2013

Focused ultrasound (FUS) in combination with microbubbles (MBs) has been successfully used in the delivery of therapeutic agents of various sizes through the blood-brain barrier (BBB) in preclinical studies. However, the dependence of delivery efficiency on the drug molecular size calls for further exploration. Fluorescence-labeled dextrans of molecular weights of 3, 70, 150, and 2000 kDa were used as model therapeutic compounds. Dextrans were mixed with MBs and injected intravenously to mice immediately after the onset of FUS sonication. The acoustic emission from ultrasound-activated MBs was acquired passively using a 10 MHz transducer and quantified for stable, inertial, and total cavitation doses. The drug delivery efficiency was quantified by the relative delivery amount and volume estimated based on fluorescent images of the brains. It was found that dextran of 3 kDa can be delivered trans-BBB at a pressure level below the inertial cavitation threshold; however, dextrans of 70, 150, and 2000 kDa were delivered only when the pressure was above the inertial cavitation threshold. At the same pressure level, the amount and volume of dextrans delivered decreased as the dextran size increased. A linear correlation of total cavitation dose and the fluorescence enhancement was found for each size dextran.
High intensity focused ultrasound for Enterococcus faecalis biofilm
Authors: Ohl Siew-Wan , Iqbal Kulsum , Khoo Boo Cheong , Neo Jennifer , Fawzy Amr Sherif
Published: November 2013

High intensity focused ultrasound (HIFU) is used to removal Enterococcus faecalis (E. faecalis) in planktonic suspension and dental biofilm. The bacteria E. faecalis is commonly found in secondary dental infection after root canal treatment. Sealed petri dish with E. faecalis planktonic suspension is placed at the focal region of the bowl-shaped HIFU transducer of 250 kHz in a water bath. It is subjected to sonification of 30 to 120 s. It is found that the HIFU successfully lysed and removed the bacteria from counting its colony forming units (CFU), performing scanning electron microscopy (SEM) and confocal microscopy. Also, E. faecalis biofilms in human teeth are subjected to the same HIFU treatment. Similar analysis is performed with SEM and confocal microscopy. It is found that after 60 s of sonification, most of the biofilm is either removed or lysed. In conclusion, this study highlights the potential of using HIFU as non-destructive dental root canal disinfection treatment.
Thermal lesion imaging using Lorentz force: Proofs of concept
Authors: Grasland-Mongrain Pol , Catheline Stefan , Mari Jean-Martial , Souchon Rémi , Zorgani Ali , Petit Alexandre , Cartellier Florian , Lafon Cyril , Chapelon Jean-Yves
Published: November 2013

The Lorentz force can be used by different means to image thermal lesions in biological tissue. In the first method presented here, so-called magneto-acoustical electrical tomography, a tissue sample is held in a magnetic field and is subsequently exposed to a focused ultrasound beam. The displacement within the magnetic field caused by this ultrasound beam results in an electrical current due to the Lorentz force. In this way, the change in electrical conductivity due to the presence of thermal lesions can then be observed. Conversely, when an electrical current is applied to tissue placed in a magnetic field, a shear wave is induced by the Lorentz force. Elastography images can be reconstructed from this shear wave, revealing thermal lesions by the change in elastic modulus. The first method was tested on ex-vivo chicken breast sample with a 500 kHz transducer and a 300 mT magnetic field. The second method was tested on gelatin phantom with a 100 mA current and 300 mT magnetic field. Images and results will be presented for both methods. These techniques could be used for the monitoring of thermal lesion formation in high intensity focused ultrasound treatment.
Rapid aberration correction for transcranial magnetic resonance-guided focused ultrasound surgery using a hybrid simulation and magnetic resonance-acoustic radiation force imaging method
Authors: Vyas Urvi , Butts Pauly Kim
Published: November 2013

Transcranial magnetic resonance-guided focused ultrasound surgery is a technique for causing tissue necrosis in the brain though the intact skull. Skull spatial and acoustic heterogeneities cause changes in the location, shape, and intensity of the focus. Current techniques use computed tomography (CT) imaging or MR-acoustic radiation force images (MR-ARFI) to correct these aberrations. CT-based techniques approximate acoustic parameters from Hounsfield units but suffer from co-registration concerns. MR-ARFI-based techniques use MR images as feedback to manipulate transducer phases, but require many image acquisitions (~4000) for one correction [Herbert, IEEE-TUFFC 56(11)2388–2399]. We demonstrate here a hybrid technique that uses one MR-ARFI image to improve the focal intensity. The hybrid simulation-MR-ARFI technique used an optimization routine to iteratively modify the simulation aberrations to minimize the difference between simulated and experimental radiation force patterns. Experiments were conducted by applying skull-based aberrations to a 1024-element, 550 kHz phased-array transducer. The experimental MR-ARFI image of the aberrated focus was used with the simulation pattern from the hybrid angular spectrum [Vyas, IEEE-TUFFC 59(6)1093–1100] beam propagation technique to estimate aberrations. The experiment was repeated three times. The hybrid simulation-MR-ARFI technique resulted in an average increase in focal MR-ARFI phase of 44%, and recovered 83% of the ideal MR-ARFI phase.
A non-axisymmetric, elongated pressure distribution in the lithotripter focal plane enhances stone comminution in vitro during simulated respiratory motion
Authors: Lautz Jaclyn M. , Sankin Georgy , Kleinhenz Joseph , Zhong Pei
Published: November 2013

A challenge in clinical shock wave lithotripsy (SWL) is stone translation due to a patient’s respiratory motion, in a direction perpendicular to shockwave propagation, which may negatively affect stone comminution while increasing the risk of tissue injury. We have developed a method using external masks and a modified lens geometry to transform the axisymmetric pressure distribution in the focal plane of an electromagnetic lithotripter into a non-axisymmetric elliptical distribution. At equivalent acoustic pulse energy (46 mJ), the peak pressure was reduced from 44 MPa to 38 MPa while the −6 dB focal width was increased from 7.4 mm for the original to 11.7 mm (major axis) and 7.9 mm (minor axis) of the modified field. In vitro stone comminution was performed in a tube holder (d = 14 mm) using a translation pattern with 12 breaths per minute and 15 mm in excursion distance. Stone comminution after 1000 shocks are 71.2 ± 4.4% and 65.2 ±8.3% (p < 0.05) along the major- and minor-axis of the modified field, respectively, compared to 62.6 ± 7.2% for the original axisymmetric field. These results suggest that an elongated pressure field aligned along the direction of stone motion may enhance stone comminution in SWL. [Work supported by the NIH and the NSF GRFP.]
Shockwave tensile phase transmission depends on the gas concentration of the coupling medium
Authors: Frank Spencer T. , Lautz Jaclyn , Sankin Georgy N. , Zhong Pei , Szeri Andrew
Published: November 2013

Previous research shows that a shockwave’s tensile phase can be strongly attenuated as a function of gas concentration in the coupling medium. Here, we seek to elucidate the relationship between tensile attenuation and gas concentration via pressure measurements at the focus and highspeed imaging. By performing in vitro experiments with water of varying gas concentrations (2.05 mg/L, 4.30 mg/L, and 6.50 mg/L), the negative impulsive pressure is correlated to the density of the bubble cloud that occurs in the beampath. It is found that for gas contents below 4 mg/L the bubble cloud remains sparse and the shockwave’s tensile phase is successfully transmitted with no loss in impulsive pressure. For gas contents 4 mg/L and above the bubble cloud becomes highly dense and prevents transmission with up to a 75% loss in impulsive pressure. Corresponding stone comminution experiments show that the treatment efficiency sharply decreases with increasing gas concentration. These results underlie the importance of degassing the water used in the coupling medium before treatment.
Fragmentation of kidney stones in vitro by focused ultrasound bursts without shock waves
Authors: Maxwell Adam D. , Cunitz Bryan W. , Kreider Wayne , Sapozhnikov Oleg A. , Hsi Ryan S. , Sorensen Mathew D. , Harper Jonathan D. , Bailey Michael R.
Published: November 2013

Shock wave lithotripsy (SWL) is the most common procedure for treatment of kidney stones. SWL noninvasively delivers high-energy focused shocks to fracture stones into passable fragments. We have recently observed that lower-amplitude, sinusoidal bursts of ultrasound can generate similar fracture of stones. This work investigated the characteristics of stone fragmentation for natural (uric acid, struvite, calcium oxalate, and cystine) and artificial stones treated by ultrasound bursts. Stones were fixed in position in a degassed water tank and exposed to 10-cycle bursts from a 200-kHz transducer with a pressure amplitude of p ≤ 6.5 MPa, delivered at a rate of 40–200 Hz. Exposures caused progressive fractures in the stone surface leading to fragments up to 3 mm. Treatment of artificial stones at different frequencies exhibited an inverse relationship between the resulting fragment sizes and ultrasound frequency. All artificial and natural types of stones tested could be fragmented, but the comminution rate varied significantly with stone composition over a range of 12–630 mg/min. These data suggest that stones can be controllably fragmented by sinusoidal ultrasound bursts, which may offer an alternative treatment strategy to SWL. [Work supported by NIH 2T32DK007779-11A1, R01 EB007643, P01 DK043881, R01 DK092197, NSBRI through NASA NCC 9-58.]
Kidney stone fracture by surface waves generated with focused ultrasound tone bursts
Authors: Sapozhnikov Oleg A. , Maxwell Adam D. , Kreider Wayne , Cunitz Bryan W. , Bailey Michael R.
Published: November 2013

Previous studies have provided insight into the physical mechanisms of stone fracture in shock wave lithotripsy. Broadly focused shocks efficiently generate shear waves in the stone leading to internal tensile stresses, which in concert with cavitation at the stone surface, cause cracks to form and propagate. Here, we propose a separate mechanism by which stones may fragment from sinusoidal ultrasound bursts without shocks. A numerical elastic wave model was used to simulate propagation of tone bursts through a cylindrical stone at a frequency between 0.15 and 2 MHz. Results suggest that bursts undergo mode conversion into surface waves on the stone that continually create significant stresses well after the exposure is terminated. Experimental exposures of artificial cylindrical stones to focused burst waves in vitro produced periodic fractures along the stone surface. The fracture spacing and resulting fragment sizes corresponded well with the spacing of stresses caused by surface waves in simulation at different frequencies. These results indicate surface waves may be an important factor in fragmentation of stones by focused tone bursts and suggest that the resulting stone fragment sizes may be controlled by ultrasound frequency. [Work supported by NIH 2T32DK007779-11A1, R01 EB007643, P01 DK043881, R01 DK092197, NSBRI through NASA NCC 9-58.]
Simulations about non-Doppler continuous wave usage of ultrasonic transducers
Authors: İkizler Emre , Sahinturk Hulya
Published: November 2013

In this work, computer simulations are executed in order to detect the presence of an object which passes through the area illuminated by ultrasonic transmitter. In simulations, object which has a constant speed can be detected by only observing received signal level on ultrasonic receiver, not by using Doppler Effect or Fast Fourier Transform. Additionally, alterations on speed and distance of the object causes sensible alterations on received signal level on ultrasonic receiver. According to simulation results, a simple way for detecting speed of objects is able to be introduced by using more simple signal processing techniques compared to Doppler Effect or Fast Fourier Transform related techniques.
Acoustics of Western and Eastern bells, old and new
Authors: Rossing Thomas D.
Published: November 2013

The modes of vibration and sound radiation from tuned church bells, carillon bells, handbells, ancient Chinese two-tone bells, and temple bells will be compared. Most bells have a circular cross section, but many ancient Chinese bells do not, and thus they have two different strike notes, depending upon where they are struck. The musical interval between these two strike notes is often near a minor third or a major third.
Evolution of the Hang percussion instrument and associated performance practices
Authors: Wessel David , Rossing Thomas
Published: November 2013

It is now over 10 years since the widespread adoption of the Hang percussion instrument. It has evolved considerably since its invention in 2000 by Felix Rohner and Sabina Scharer in Bern, Switzerland. We present acoustical analyses of variations of the instrument in conjunction with an evolving performance technique. The talk will include demonstrations of performance practices and their acoustical consequences.
Active noise control: Eight decades of research and applications
Authors: Cunefare Kenneth
Published: November 2013

On January 27, 1933, Paul Lueg submitted his patent application for an active noise control system. In the intervening 80 years, the concept has progressed from simple single-input single-output feedback control systems through to complex MIMO approaches implementing a seemingly endless variety of control algorithms. Academic publications appear to continue at approximately a constant pace over the past decade, with much attention paid to algorithm refinement and development of applications. Commercial successes of active noise control include ANC headset in the aviation and consumer markets, as well as systems installed in passenger vehicle (some of which also incorporating active vibration control systems). This paper will provide a brief historical retrospective on the development of active noise control, and survey the current state of academic research as well as existing and proposed production applications (consumer, aviation, defense, etc.).
Strategies for improving speech intelligibility and warning signal detection in communication headsets/hearing protectors
Authors: Brammer Anthony J. , Bernstein Eric R. , Yu Gongqiang
Published: November 2013

Strategies for improving speech understanding and warning signal detection when wearing communication headsets/hearing protectors (HPDs) in environmental noise must accommodate sounds from different sources at different times. A subband signal processing approach would appear desirable, with a delayless structure essential for active noise reduction (ANR). The requirements for communication channel and ANR controllers differ, owing to the different bandwidths required for speech and warning signals, and for ANR. Subbands for optimizing speech signal-to-noise ratios are commonly fractional-octave bandwidth, while computational efficiency favors linear subbands for ANR. Increasing the number of subbands reduces computational cost for the latter but the advantage is less apparent for communication signal control. Possibilities exist for harmonizing subband filter structures by constructing models of speech intelligibility using computationally efficient bandwidths. In contrast, algorithms for detecting warning sounds tend to be governed more by audibility than bandwidth considerations. The issues will be discussed using a simulation of a circumaural HPD that can replicate word scores obtained by a subject when subject-specific transfer functions are employed. Where available, results from physical devices and subjects will be included, as well as the consequences of differences in individual auditory abilities. [Work supported by NIOSH grant R01 OH008669.]
A better frequency domain adaptive algorithm for active noise control in a short duct
Authors: Lu Jing , Qiu Xiaojun
Published: November 2013

For the feedforward active noise control in a short duct, the noncausality of the whole system is often inevitable, since the reference sensor needs to be placed very close to the control source, and the acoustic transmission delay between them is often surpassed by the inherent AD/DA and anti-aliasing filters latency in the controller. The commonly used normalized frequency domain LMS algorithm possesses the benefit of fast convergence speed, but suffers from deteriorated steady-state performance when used in non-causal circumstances. In this paper, an efficient modification of the normalized frequency domain LMS algorithm is proposed, which can significantly improve wide-band noise reduction level in non-causal circumstances. Both simulations and experiments demonstrate the superiority of the proposed algorithm.
Current developments in practical active damping systems for vibration-isolated platforms
Authors: Ryaboy Vyacheslav
Published: November 2013

The paper discusses recent developments in practical implementation of the active damping solution for vibration isolated platforms (optical tables) known as Smart Table. The system implements a decentralized velocity feedback with sensors and actuators integrated into the platform. It proved effective in creating vibration-free environments for sensitive experiments and precision manufacturing processes in life sciences, nanotechnologies and other areas. The paper describes expansion of the technology to larger platforms characterized by lower resonance frequencies. The technical difficulties related to interference between the resonance properties of the structure and the resonance of the electromagnetic actuator (see Elliott and Baumann, J. Acoust. Soc. Am. 121(5), 2007) were addressed successfully. Other developments required by expansion of the area of applications included introduction of dampers acting in all directions, as well as a portable modular version of the active dampers.
Observations on geomagnetic auroral infrasound waves 2003—2013
Authors: Oldham Justin J. , Wilson Charles R. , Olson John V. , Szuberla Curt , Nielsen Hans
Published: November 2013

Persistent, high trace velocity infrasound activity, associated with auroral events, has been routinely observed from the CTBT/IMS I53US infrasound station in Fairbanks. Comparisons of the infrasound data with data from the Geophysical Institute Magnetometer Array, the Poker Digital All-Sky Camera, and historic data from the Poker Flat Imaging Riometer show that the observed infrasound is correlated with periods of heightened geomagnetic activity and is produced in the lower Ionosphere. With the infrasound array operating near-continuously now for roughly one full period of the solar cycle, we have systematically isolated all such geomagnetic auroral infrasound events to form a data set suitable for statistical analysis. We note a relationship between the occurrence of geomagnetic infrasound waves (GAIW) and the recovery phase of geomagnetic storms when the geomagnetic H component has a peak-to-peak amplitude of ~1500 gamma during the local time period from 5 to 10 h at the CIGO Magnetic Observatory in Fairbanks. During this time interval I53US is under the auroral oval when there are large pulsating aurora events that produce infrasonic waves. These observations restrict the apparent source geometry and generating phenomena of the infrasound, as well as providing a basis for comparison with idealized models of GAIW generation.