bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave scattering and interaction in elastic sea beds.
Authors: Ivakin Anatoliy N. , Jackson Darrell R.
Published: July 2011

A first-order perturbation model of scattering in an elastic medium is revisited and discussed. The material properties of the medium are defined by three spatially fluctuating variables, the density and two Lamé parameters. The wave interaction process is described in terms of four mechanisms of scattering and energy conversion: two without change of the wave type, from compressional to compressional and from shear to shear, and two with the type conversion, from compressional to shear and vice versa. The model is applied to the case of acoustic scattering from and propagation in underwater sediments of different types, sand and rock. Wave interaction and attenuation due to various mechanisms of scattering in the sediment are considered. An improved method for calculation of the seabed scattering strength is proposed, which takes into account the so-called “windowing” effect. It allows more accurate accounting for the contribution of volume heterogeneities near the sediment surface and its comparison with the first-order roughness mechanism of scattering. The frequency-angular dependencies of the scattering strength for elastic sandy and rocky seafloors are calculated, and behaviors of the volume and roughness contributions are compared.
The physics of biomedical imaging and therapy by interacting light and sound.
Authors: Roy Ronald A.
Published: July 2011

Light and sound waves propagating through tissue are coupled in useful and interesting ways. When a beam of sound travels through diffuse light, photons passing through the beam are phase modulated at the ultrasound frequency, yielding information on tissue optical and acoustical properties via the acousto-optic (AO) effect. Alternatively, the absorption of short-pulse laser light induces rapid heating that launches acoustic waves that can then be used to determine the spatial distribution of optical absorption, a phenomenon referred to as the “optoacoustic” or “photoacoustic” (PA) effect. We will present a phenomenological introduction to the emerging field of dual-wave sensing and imaging using light and sound, give a few illustrative examples, and comment on the potential for applying these concepts to tissue imaging. We then transition from imaging mode to therapy mode by introducing a high-intensity focused ultrasound (HIFU) beam that can (1) pump the AO interaction, (2) enhance the level of PA emissions, or (3) promote cavitation-mediated therapy. We include a brief review of the physical and biological effects of HIFU-induced cavitation and will discuss how the addition of light and nanoparticles enhances both the efficacy and targeting accuracy of HIFU therapy in optically diffuse tissues such as breast and brain.
Memories of Manfred Schroeder at Bell Telephone Laboratories: 1955–1987.
Authors: Mathews Max
Published: July 2011

Manfred joined Bell Labs in late 1954 and I joined in the middle of 1955. We both retired in 1987. We and our families became close friends. This was a golden age of research at Bell Labs. ATT, a regulated monopoly with a steady source of income and a great need for new technology, well supported the research. In 1969 Manfred took a second job as head of the Third Physical Institute (Acoustics) at Goettingen, Germany, but continued working at Bell Labs, interacting closely with Bishnu Atal. Manfred’s speech work led to encodings to reduce the bits needed to transmit speech. Manfred showed one does not need to encode the parts of sounds which the ear does not hear due to masking by the ear itself. He was strongly interested in number theory and used it to design colorless diffusing panels for auditoriums. He developed reproducible white noise signals to test auditoriums. He also designed colorless digital reverberators for music. Manfred and I were incredibly lucky to have lived in such an exciting time and worked at such great institutions.
Manfred R. Schroeder as an academic teacher: Minutes from an infinite paradise in acoustics, number theory, and “swinging physics.”
Authors: Kollmeier Birger
Published: July 2011

Being the academic supervisor of more than 40 Ph.D. students (that later became university professors or chief scientists in companies themselves) constitute only a small part of the many activities and scientific fields Manfred R. Schroeder mastered in his academic life. After finishing his Ph.D. with Erwin Meyer in Gottingen (1954) Schroeder joined Bell Labs where he finally became director of acoustics and mechanics research. In 1969 he was also appointed Professor of physics and director of the Drittes Physikalisches Institut in Gottingen. The denomination of the institute “Schwingungsphysik” (i.e., physics connected to oscillations) was deliberately mistranslated by him into “swinging physics”—a term that characterizes well the light mood and creative atmosphere among the students that was inspired by Schroeder’s supportive character in the 70’s–90’s. His inventions and impressive lectures about acoustics, number theory, speech, and nonlinear dynamics formed the basis of his very popular books. The “Schroeder diffusors,” for example, are reflection gratings based on his number theoretic considerations that suppress the specular reflections while distributing scattered sound into all different directions. The talk will give an overview of Manfred Schroeder’s life in academia—from the viewpoint of one of his former students.
Manfred R. Schroeder: Challenge the present and there is a better way.
Authors: Atal Bishnu S.
Published: July 2011

I worked with Manfred Schroeder for about 25 years at Bell Telephone Laboratories starting in May 1961. The entrance hall of the Bell Labs building at Murray Hill, NJ had an inscription attributed to Alexander Graham Bell that said “Leave the beaten track and you will find something you have seen never before.” Manfred always inspired me to look for things one has never seen before. Digital computers were emerging in the 1960s with great promise and we used computers to do many new things: simulation of acoustics of concert halls, studying sound decay in rooms using ray tracing, and producing high-quality speech at low bit rates. This paper will highlight a few examples. Manfred had been deep in the area of vocoder research then, but we started on a new track leading us ultimately to code-excited linear prediction. This set the spark for expanding the use of cell phones worldwide. As a manager, Manfred Schroeder was uncompromising in pushing for scientific excellence resulting in success; Bell Labs had a fearsome reputation of being the best.
Spatial audio and room acoustics.
Authors: West James E. , Atkins Josh
Published: July 2011

Schroeder’s interest in the behavior of sound in small enclosures eventually lead to the use of statistical methods of digital signal processing to estimate and track a room’s response for echo control. He showed that a small frequency shift (5 Hz) in a loudspeaker-enclosure-microphone system could be used to mitigate the coupling feedback in public address systems. He also employed frequency shifting for echo and feedback control in the first stereo teleconferencing system. We use many of the results from the early work on stereo teleconferencing in developing solutions for multichannel, immersive systems. Schroeder’s work on simulating room acoustics form the fundamentals of how we simulate and test new algorithms. His work on stereo reproduction and perception forms the basis for our motivation to explore multichannel systems (specifically, the spatial release from masking effects). The work on frequency shifting in public address systems was a first attempt at a problem that research is still focused on, multichannel acoustic echo cancellation, which addresses the howling feedback and echo that results from a loudspeaker-enclosure-microphone system.
Are impulse responses Gaussian noise?
Authors: Polack Jean-Dominique
Published: July 2011

Many years ago, Manfred Schroeder proved that transfer functions in rooms follow complex Gaussian distributions. This property was extended to impulse responses by the author, following a suggestion by Moorer for simulating impulse responses. More recently, several authors have checked again the later property with modern signal analysis tools. They obtained mixed success, with results that strongly depend on the length of the analysis window. In order to understand these unstable results, the present paper takes a closer look at the statistical distributions of both impulse responses and transfer functions. It shows that an accurate model of both the impulse response and the transfer function is necessary in order to test the distribution. Further, it presents several sources of artifacts that skew the distributions and shows that they can be ascribed to the signal processing methods used to extract the responses. Finally, the conditions for obtaining true Gaussian distributions are specified.
Neurally-based acoustic and visual design.
Authors: Ando Yoichi
Published: July 2011

Our earlier approaches to acoustic design drew from sources outside the listener’s nervous system: external acoustical measurements, cochlear biophysics, and overt psychoacoustical judgments [Schroeder, “Model of hearing,” Proc. IEEE 63, 1332–1352 (1972)]. In more recent years, we have also attempted to ground acoustic design in terms of brain processes that subserve auditory percepts and preferences. Neural response correlates associated with auditory qualities related to central autocorrelation functions (temporal sensations such as pitch, timbre, and loudness) and those related to interaural crosscorrelation functions (spatial sensations) were found to be dominant in one or another cerebral hemisphere. Features of these two central correlation functions describe primary auditory qualities well. The observable neural correlates of subjective preferences and annoyances involve the temporal persistence and spatial extent of EEG and MEG alpha rhythms in cortical regions. Analogous percepts, preferences, and correlation-based representations have been explored for a number of visual patterns (flickers, oscillating objects, and textures). Subjective scale values of listener preferences for sounds, sound fields, and visual patterns all show the same cortical alpha rhythm persistence and extent [Ando, Auditory and Visual Sensations, Springer-Verlag, (2009)]. Rational design of sensory experience is possible given a theory of stimulus generation and modification, percepts, and preferences. In acoustics, adaptive methods can be used to optimize concert hall sound fields, musical instruments, and speech recognition.
In vivo measures of hearing in seals via auditory evoked potentials, otoacoustic emissions, and computerized tomography.
Authors: Ketten Darlene R. , Williams C. Rogers , Mooney T. Aran , Matassa Keith , Patchett Kristen
Published: July 2011

Dr. Schusterman and Dr. Kastak made significant contributions to our basic understanding of pinniped hearing but recognized also that data, particularly from older animals, could reflect abnormalities. This concern is particularly acute for stranded animals and species for which we lack baseline data. Approximately 20% of stranded seals are estimated to have ear infections, which if undetected and untreated can lead to septicemia and death. In this study, five harbor seals (Phoca vitulina) with suspected infections were examined with CT, OAE, and AEP to determine hearing test diagnostic correlates of ear pathologies. OAEs were obtained between 0.5 and 15 kHz. AEPs were obtained from 1–30 kHz. CT, AEP, and OAE results were assessed independently. Four animals had moderately elevated thresholds but normal brainstem responses, consistent with CT findings of conductive loss from occluded middle ears but normal inner ears. Differences in percent occlusion over time and across individuals were consistent with threshold variations. A fifth animal with no overt signs of infection but scans showing aggressive inner, middle, and external ears disease, had no responses within 70 dB of normal response ranges. These data demonstrate that OAE/AEP features are important diagnostic tools for treatment and rehabilitation decisions. [Work supported by the ONR.]
Temporary hearing threshold shifts and recovery in a harbor porpoise (Phocoena phocoena) and harbor seals (Phoca vitulina) exposed to white noise in a 1/1-octave band around 4 kHz.
Authors: Kastelein Ronald , Gransier Robin , van Mierlo Ron , Hoek Lean , de Jong Christ
Published: July 2011

To set safety criteria for levels of sounds produced during pile driving for offshore wind parks, temporary hearing threshold shifts (TTSs) were studied in a harbor porpoise and two harbor seals. A psychoacoustic behavioral technique was used to quantify TTS and hearing recovery in the animals exposed to underwater sounds (white noise in a 1/1-octave band around 4 kHz). Hearing thresholds were determined once a day for a narrow-band frequency swept sine wave (3.9–4.1 kHz) before and after exposure to the fatiguing noise, which was offered at two sound pressure levels (131 and 119 dB re 1 μPa for the porpoise and 151 and 139 dB re 1 μPa for the seals) each at four durations (15, 30, 60, and 120 min). Recovery was quantified by measuring hearing thresholds at 4, 8, 12, and 48 min after the noise exposure. The results show that TTS in harbor porpoises occurred at a sound exposure level threshold approximately 20 dB below the threshold for which TTS occurred in harbor seals.
Behavioral reactions of dolphins and sea lions to sonarlike sound exposures.
Authors: Houser Dorian S. , Yeates Laura , Crocker Daniel E. , Martin Steve W. , Finneran James J.
Published: July 2011

Colleagues Ron Schusterman and Dave Kastak were instrumental in the advancement of marine mammal cognition and sensory biology studies. In the past 2 decades, their work was heavily concerned with the potential impact of anthropogenic sound on pinnipeds. Behavioral reactions of marine mammals to anthropogenic sound exposure are one impact with a large range of potential consequences. Recently, 30 dolphins and 15 sea lions were exposed to sonarlike pings used in antisubmarine warfare. Exposures occurred while animals performed a behavior in which they traveled from one location to a second where they touched a paddle, and then returned for a food reward at the starting location. Subjects performed a ten trial baseline session followed by a ten trial experimental session in which sound exposures occurred. Each subject was randomly assigned a receive level from near ambient to 185 dB sound pressure level. For each subject, received levels were consistent across all experimental trials. Behavioral reactions were anticipated prior to the study and assigned a severity score by a panel of anonymous reviewers. Scores were used to explore relationships between the received level and the severity of the behavioral response.
Auditory habituation as a diagnostic measure of domoic acid toxicosis in wild sea lions.
Authors: Cook Peter , Reichmuth Colleen , Gulland Frances
Published: July 2011

Habituation measures are instrumental in behavioral neuroscience, but they have seldom been applied to research with marine mammals. In this study, an auditory habituation paradigm was applied as a diagnostic tool in California sea lions with suspected brain damage resulting from neurotoxic exposure to domoic acid. Domoic acid is a glutamate agonist that causes damage to the hippocampus and surrounding medial temporal areas. Such damage is typically revealed only by brain imaging or postmortem histology, and is therefore difficult to diagnose in a veterinary setting. Studies of laboratory animals suggest that habituation of defensive responses to aversive stimuli does not generally rely on hippocampal function, while habituation of orienting responses to non-aversive stimuli has been shown to rely on this brain area. Here it was found that behavioral orienting responses to a series of non-aversive sounds habituate more slowly in sea lions with domoic acid toxicosis than in sea lions with no apparent neurological deficits. A signal detection analysis indicates that a measure based on this habituation shows significant diagnostic value. Preliminary results of a follow-up procedure probing habituation and dishabituation to auditory stimuli presented from multiple locations are also discussed. [Work supported by NSF Graduate Fellowship].
Preliminary investigation of sound reception in southern sea otters (Enhydra lutris nereis).
Authors: Ghoul Asila , Reichmuth Colleen
Published: July 2011

Due to their dependence upon a highly restricted coastal habitat, sea otters are vulnerable to a variety of environmental and anthropogenic threats. Among these is the potential disturbance from human-generated sources of noise. Presently, there are no data on the auditory sensitivity of sea otters, and little evidence to suggest what sounds may be most relevant to these animals. As an initial step toward describing the acoustic sense of sea otters, we conducted a controlled exposure experiment, adapted from sound exposure studies used in behavioral field research, to efficiently measure the aerial frequency range of hearing in four captive sea otters. This approach was designed to determine which frequencies were audible to each animal, rather than to provide direct measures of auditory sensitivity. The maximum range of aerial hearing determined using this method was 0.125 to 32 kHz. These are the first direct measurements of hearing obtained for sea otters, and the results are relevant to improving understanding of their acoustic communication, evolutionary biology, and behavioral ecology, as well as in supporting ongoing conservation efforts. This research effort draws from the work of Kastak and Schusterman, especially with respect to the value of behavioral baselines in captive studies of marine mammals.
Long-term monitoring of bocaccio abundance using passive acoustics.
Authors: Širović Ana , Demer David
Published: July 2011

The bocaccio (Sebastes paucispinis) was a part of an important rockfish fishery to California anglers and commercial fishers until they were declared overfished by the Pacific Fisheries Management Council in 1999. Historically, rockfish stocks were estimated using ichthyoplankton sampling and catch per unit effort of the rockfish recreational fishery. More recently, with the closure of the fishery, non-lethal methods for stock assessment have been in development such as a combination of shipboard multifrequency echosounders and underwater cameras. To augment these methods, passive acoustics have been shown to be a possibility for long-term monitoring, but a further investigation in its use for rockfish population monitoring is necessary. Sounds produced by bocaccio were recorded off San Clemente Island in the Southern California Bight in the 1960s by Thompson, and again at a near-by location in 2007. A comparison of these recordings with the contemporary population estimates for bocaccio in the area will shed a light in the feasibility of using passive acoustics for long-term monitoring of changes in the population abundance of this commercially important species.
Convergent evolution and intermediate status of the sonic mechanism in a perciform fish Glaucosoma buergeri (Glaucosomatidae).
Authors: Fine Michael L. , Mok Hin-Kiu , Tsai Kai-Yun , Chiu Pai-Ho , Parmentier Eric
Published: July 2011

Little is known about evolution of swimbladder sound production in fishes. Typical fish sound production utilizes fast muscles that drive the swimbladder to produce sound as a forced but rapidly-damping response; a muscle contraction rate of 200 times/s will generate a sound with a fundamental frequency of 200 Hz. Recently, slow muscles have been demonstrated in a carapid fish. These muscles slowly extend the anterior swimbladder by stretching a swimbladder fenestra until the bladder snaps back exciting sound production. Here we describe sounds produced by a similar but phylogenetically-unrelated mechanism in a perciform fish. A pair of extrinsic sonic muscles originates on the pterotic bones and inserts on the anterodorsal swimbladder just forward of a stretchable swimbladder fenestra. A fan-shaped tendon that ends in a smooth muscle attaches to the bladder just forward of the fenestra. The tendon-smooth muscle pair will be stretched by contraction of the rostral sonic muscles. Strain energy stored in the tendon will cause the anterior bladder to recoil upon muscle relaxation. Sound pulses consist of two parts: a low-amplitude one followed by a higher frequency higher amplitude part. We suggest that the first part of the call is caused by contraction of the anterior sonic muscle (cocking) and the second (release) is forced by strain energy in the stretched tendon and smooth muscle.
Acoustic, visual, and chemical signaling during courtship in an African cichlid fish.
Authors: Maruska Karen P. , Fernald Russell D.
Published: July 2011

The ability to attract and assess the quality of potential mates is critical for reproductive success, but few studies examine coincident multimodal sensory cues used for reproductive signaling within a single species. Here we examined acoustic, visual, and chemical signaling used by male African cichlid fish (Astatotilapia burtoni) during reproduction. Dominant males produced pulsed sounds in tight association with visual courtship displays where their bodies quivered vigorously in close proximity to a female. Sound production always occurred with visual courtship displays, but not all body quivers were associated with sound, which supports the hypothesis of intentional acoustic communication. Peak frequency of courtship sounds decreased with increasing male body size, possibly providing females with an honest signal of quality. Male chemical signaling, visualized as urine pulses, was higher in the presence of gravid compared to non-gravid females, but did not occur during any specific acoustic or visual courtship displays. These data suggest that dominant males use acoustic, visual, and olfactory channels at different times during courtship possibly to convey distinct types of information such as social/dominance status, motivation to spawn, and fitness.
Derivation of a response severity index model for physiological quantification of fish response to impulsive sound.
Authors: Halvorsen Michele B. , Woodley Christa M. , Casper Brandon , Carlson Thomas J. , Popper Arthur N.
Published: July 2011

Assessment of the effects on fish from exposure to impulsive and other sound has been limited by the ability to quantify physiological injuries, which range from mortal to recoverable. Over the past several years, a panel of measures has evolved that includes postexposure assessments of external injury, internal injury in response to rapid decompression, impulsive sound, and explosive sound exposures. This has led to a model that permits reduction in a complex panel of injuries into a single metric. Computation of the metric considers the rank of the injury by its physiological significance to the condition of exposed fish and the severity of observed injuries. The metric has been found to have a wide dynamic range in that it is sensitive to the onset of injury at very low intensity exposures through mortal injuries at severe exposures. The model accommodates normalization of outcomes between experiments separated in time, which utilize separate fish populations by accounting for the condition of fish in addition to experimental control strategies. The model is explained, and its use in derivation of an exposure-response function for juvenile Chinook salmon exposed to impulsive sound is presented.
Recovery from exposure to pile driving signals by Chinook salmon.
Authors: Casper Brandon M. , Matthews Frazer M. , Halvorsen Michele B. , Carlson Thomas , Popper Arthur N.
Published: July 2011

Juvenile Chinook salmon exposed to pile driving sounds showed a variety of barotrauma injuries immediately post-exposure, with number and severity of injuries increasing with increased cumulative sound exposure levels (SELcum). Important remaining questions pertain to the severity of these injuries over time post-exposure including whether (a) injuries are eventually mortal, (b) new injuries show up, or (c) there is recovery over time. Juvenile Chinook salmon were exposed to either high or low SELcum pile driving stimuli. Fish were assessed for barotrauma injuries immediately following exposure and at 2, 5, or 10 days post-exposure. No fish died during recovery and all fish exhibited normal feeding behavior within hours of exposure. The injuries observed at day zero were comparable to those found in the previous pile driving studies at the same SELcum. However, beginning with day 2, the frequency of appearance of injuries began to decrease, with fish at day 10 showing few remaining injuries. These results suggest that Chinook salmon exposed to pile driving stimuli have the potential to recover from barotrauma injuries, and that new injuries did not show up post-exposure. These are important findings that need to be considered when establishing exposure criteria for pile driving projects.
Mechanically-induced hair cell death using the zebrafish lateral line as a model system.
Authors: Lu Zhongmin , Frye Maxwell A. , DeSmidt Alexandra A.
Published: July 2011

Noise-induced hearing loss is a major type of hearing impairment that affects the quality of life for millions of Americans. The cause of noise-induced hearing loss is the death of sensory hair cells in the ear. The primary goal of the present study is to have a better understanding of mechanisms underlying noise-induced hearing and balance deficits. Mechanically-induced hair cell degeneration was investigated using the zebrafish (Danio rerio), which has become a model system for biomedical research because of a combination of powerful genetics, excellent embryology, and exceptional in vivo visualization in one organism. Zebrafish have the lateral line system containing superficial neuromasts in the head and trunk, and each neuromast has a cluster of hair cells that structurally and functionally resemble the hair cells in the ear. In this study, hair cells in single neuromasts of zebrafish larvae of 5 to 10 days post fertilization were stimulated by a piezoelectric actuator and the time course of degeneration of hair cells exposed to overstimulation was obtained using light microscopy. Microphonic potentials of neuromast hair cells were also recorded to show effects of intense mechanical stimulation on the function of hair cells. [Work supported by NIH/NIDCD R21DC009879 and Gabelli Fellowship.]
Testing mortality of fish larvae due to simulated offshore piling noise.
Authors: de Jong Christ A.F. , van Beek Pieter J.G. , Ainslie Michael A. , Bolle Loes J. , van Keeken Olvin A. , van Damme Cindy J.G. , Winter Hendrik V. , de Haan Dick
Published: July 2011

Driven by the concern that impulsive noise produced by offshore pile driving may lead to mortality of fish larvae, a device was developed for testing the sensitivity of small fish and fish larvae to sound exposure. The device consists of a rigid-walled cylindrical chamber (110-mm diameter, 160-mm height), driven by an electrodynamical sound projector. Samples of up to 100 larvae can be exposed simultaneously to a homogeneously distributed sound pressure and particle velocity field, at a controllable static pressure up to 3 bars. Two configurations are available with either a dominant sound pressure or a dominant particle velocity exposure. Recorded piling noise can be reproduced in a controlled way, in the frequency range between 50 Hz and 1 kHz, at zero to peak pressure up to 40 kPa and single pulse sound exposure levels up to 187 dB re 1 μPa2 s, or peak particle velocity up to 2.2 cm/s and integrated square particle velocity level 124 dB re 1 (nm/s)2 s. Tests are carried out in which sole (Solea solea) larvae at different stages of development were exposed to various levels and durations of piling noise.
Two-dimensional real-time ultrasound technique to control lesion size during high intesity focused ultrasound therapy.
Authors: Petruzzello John , Anand Ajay , Zhou Shiwei , Sethuraman Shriram , Azevedo Jose
Published: July 2011

The lack of an accurate low-cost technique for real-time monitoring of ablative therapies such as HIFU has limited its clinical adoption. Ultrasound based monitoring would enable a more widespread usage of HIFU therapy. We have developed an acoustic radiation force (ARF) based technique for controlling the lesion size and placement during HIFU therapy. A series of experiments were performed in excised bovine liver tissue to evaluate the proposed technique. Two different parameters were developed to perform real-time monitoring of lesions. The first parameter, normalized displacement difference (NDD), is defined as the difference between normalized displacement induced by ARF at the therapy endpoint and a reference determined from the data. This parameter was accurate in determining lesion sizes below 8 mm in diameter as independently determined by histological examination. The lesion dimensions estimated with this noninvasive approach matched histology to within ±2 mm. A second approach was based on the saturation of displacement as treatment progressed. This technique was accurate (>2 mm) for all lesions examined. Both the NDD and displacement saturation techniques were independent of treatment time and power. This study demonstrates potential for use of these techniques in real-time monitoring of HIFU therapy to determine therapeutic endpoint and improve treatment efficacy.
Characterization of high intensity focused ultrasound induced thermal lesions from changes in ultrasound backscatter.
Authors: Jean-Yves Chapelon , Jeremy Chenot , Remi Souchon , David Melodelima
Published: July 2011

Although good results have already been obtained, notably in urology, ultrasound-guided HIFU devices lack a real time monitoring system different from conventional B-mode ultrasound imaging to check the efficacy of the treatment procedures. This presentation describes the development and assessment of several noninvasive procedures developed in our laboratory for making local measurements of attenuation variations, strain changes, and/or temperature increases during HIFU treatment procedures. The techniques to characterize lesions generated by HIFU are based on estimation of relative changes in tissue properties derived from backscattered rf data. Our recent work has demonstrated good agreements between ultrasound backscattering changes versus temperature increase and thermocouple measurements. In ex vivo liver samples, a linear relationship between changes in the radiofrequency signal and temperature was found for temperatures up to 90 °C. Using differential imaging, any issues related to the heterogeneity of the medium is eliminated, since only changes in attenuation, strain, and temperature of tissue are taken into account. These ultrasound techniques can be used during in vivo treatment procedures and they can be easily implemented in real time.
Near real time evaluation of cardiac radiofrequency ablation lesions with intracardiac echocardiography based acoustic radiation force impulse imaging.
Authors: Wolf Patrick D. , Eyerly Stephanie A. , Bradway David P. , Dumont Douglas M. , Bahnson Tristram D. , Nightingale Kathy R. , Trahey Gregg E.
Published: July 2011

[Cardiac radiofrequency (rf) ablation is used to treat cardiac arrhythmias. Multiple rf lesions are created to form lines of electrical block to disrupt arrhythmic wavefronts. However, image based lesion evaluation is not performed and clinicians rely on changes in electrical propagation to evaluate lesion quality. A near real time lesion evaluation system was developed and tested in vitro and in canines using acoustic radiation force impulse imaging (ARFIi) combined with a catheter tracking system (CARTO, Biosense Webster). rf ablation was performed and delivery sites were indicated on a CARTO electroanatomic map. A CARTO spatially tracked SoundStar® catheter was then used to steer the imaging plan to transect lesions, and intracardiac echocardiography (ICE) based ARFIi (Siemens, S2000 Acuson) was used to evaluate lesion contiguity and transmurality. Imaging was gated to diastole when unablated tissue is soft; motion filtering was employed to reduce the effects of catheter and cardiac movement. ARFIi based evaluation of rf lesions demonstrated a resolution of less than 2mm in vitro and lesion assessment correlated with electrical block in animal studies (λ=0.8). Combining catheter tracking with ICE based ARFIi allows near real time evaluation of cardiac ablation lesions. [Work supported by Siemens Medical, Biosense Webster, and NIH Grant No. R01-EB-012484 and R37-HL096023.]
Ultrasound-based targeting and monitoring of high intensity focused ultrasound fields.
Authors: Curra Francesco P. , Owen Neil
Published: July 2011

A new method to address the challenging tasks of image-guidance, targeting, and treatment monitoring during HIFU treatments is presented. The approach, enabled by the use of a novel multi-layer PZT-PVDF array with broad receive bandwidth in conjunction with a programmable ultrasound engine, uses the passive-mode received echoes of the imaging array with a custom pixel-based beamforming for HIFU focal tracking and targeting, allowing real-time two-dimensional (2D) B-mode visualization of the HIFU beam. Temperature monitoring during treatment is based on acoustic nonlinear propagation theory and the physical relationship of sound speed and attenuation to frequency and temperature. The harmonics-rich received echoes are processed differentially, encoded into an RGB additive color channel, beamformed, and overlayed in color over regular B-mode images. Dynamic local temperature changes in the region of interest become visible as the 2D color image changes from frame to frame. Preliminary results on beam visualization and temperature estimations during HIFU exposure in ex-vivo muscle tissue will be presented. [Work supported by NIH NIDDK].
Imaging and monitoring non-cavitating focused ultrasound lesions using light and sound.
Authors: Roy Ronald A. , Lai Puxiang , McLaughlan James R. , Draudt Andrew B. , Cleveland Robin O. , Murray Todd W.
Published: July 2011

Acoustically imaging non-cavitating HIFU lesions is challenging due to the relatively weak contrast between normal and necrosed tissues. However, thermal lesions posses optical scattering and absorption characteristics that can differ significantly from surrounding tissue. Acousto-optic (AO) sensing refers to the detection of phase modulated photons generated by the nonlinear interaction of diffuse laser light (532 and 1064 nm) and a focused ultrasound beam. AO sensing in excised chicken breast exposed to HIFU (1.1 MHz) is used to sense the onset and spatial extent of lesion formation in real time and to image an existing lesion after HIFU exposure. We also demonstrate that the AO signal can be used to provide real-time feedback in order to more effectively control the duration of the HIFU exposure. [Work supported by the Center for Subsurface Sensing and Imaging Systems (NSF ERC Award No. EEC-9986821).]
Quantitative ultrasound assessment of thermal therapy in liver.
Authors: Kemmerer Jeremy P. , Oelze Michael L.
Published: July 2011

High-intensity focused ultrasound (HIFU) is a promising modality for non-invasive therapy with application to cancer treatment. Non-invasive monitoring and assessment of HIFU remains a critical hurdle to widespread clinical acceptance of HIFU. Quantitative ultrasound (QUS) is a novel approach for characterizing tissue microstructure that shows promise for monitoring and assessment of HIFU therapy. The QUS parameters of effective scatterer diameter (ESD) and effective acoustic concentration (EAC) were examined differentially in rat liver specimens exposed to HIFU to form visible lesions. Increases in ESD of 15% and decreases in EAC of 3 dB were observed in post-exposure compared to pre-exposure scans, and statistical significance was observed in most cases (p < 0.05). These results were compared to rat liver samples heated in a water bath, in which the samples were heated to a therapeutic temperature (60 °C) for several minutes, and ultrasonic backscatter was measured at 37 °C. ESD was observed to decrease by an average of 15% in exposed compared to unexposed sample sections. [Work supported by NIH R01EB008992.]
The application of phase-shift nanoemulsion in high-intensity focused ultrasound-mediated heating and its potential in monitoring lesion formation.
Authors: Zhang Peng , Porter Tyrone
Published: July 2011

Phase-shift nanoemulsion (PSNE) consists of dodecafluoropentane nanodroplets stabilized with phospholipid monolayer shell. These nanodroplets are pressure sensitive and can be vaporized into gas bubbles by a short ultrasound pulse (t<50 ms), provided the pressure exceeds a well-defined threshold. This property provides means of on-site and on-demand nucleation by applying PSNE into high-intensity focused ultrasound. In this study, the bubble-enhanced lesion formation with the presence of PNSE in albumin-containing gel phantom was investigated. The results demonstrated that the onset of bubble-related heating could be well controlled by choosing the vaporization time and the bubble location was confined at the HIFU focal region. By acoustically driving the vaporized bubbles, localized bubble-enhanced heating and a significant reduction of 71.9% in acoustic power were achieved. Furthermore, the vaporized bubbles can be monitored with B-mode ultrasound due to the huge difference between gas and tissue. By comparing the optical image of lesion and ultrasound image of bubble cloud, a good correlation in location and shape between lesion and bubble cloud was observed. The correlation suggests that the bubble-enhanced heating is localized at the region of bubble cloud. By monitoring cavitation activity, the spatial information of lesion formation could be provided during HIFU treatment.
Microphone arrays for the measurement and modeling of vertical take-off and landing aircraft.
Authors: McKinley Richard L. , Gallagher Hilary L. , McKinley Robert C.
Published: July 2011

Jet aircraft, which have vertical take-off and landing capabilities, presents special noise measurement and source modeling challenges. When the aircraft is high above the ground, the predominant source is the jet plume/plumes. When the aircraft is close to the ground, the jet impingement becomes a second major source. Aircraft height above ground, weight, wind, and power setting all are important variables to consider for measurement and source modeling. This paper will review full scale measurements and source modeling conducted on legacy aircraft such as the AV-8B Harrier and considerations for the measurement and source modeling of new aircraft with vertical capabilities.
Characterizing nonlinearity in jet aircraft flyover data.
Authors: Downing J. Micah , Gee Kent L.
Published: July 2011

Various analysis techniques have been proposed as means of characterizing acoustical nonlinearities in high-thrust engine noise. These include probability distributions for the pressure and the time derivative of the pressure (i.e., the gradient), the skewness and kurtosis coefficients of the pressure and its time derivative, and ordinary and higher-order spectral measures. In this paper, a number of these analyzes are evaluated using acoustic data recorded during various military jet flyovers.
Simulation of rotary and fixed wing flyover noise for subjective assessments.
Authors: Rizzi Stephen A. , Aumann Aric R. , Allen Matthew P. , Burdisso Ricardo A. , Faller Kenneth J.
Published: July 2011

Subjective assessments of noise from aircraft flight operations require time histories of acoustic pressure at listener positions. Synthesized sound has an advantage over recordings by allowing the examination of proposed aircraft, flight procedures, and other conditions or configurations for which recordings are unavailable. Previous work by the authors [J. Acoust. Soc. Am. 113, 2245 (2003); 114, 2340 (2003); 116 2515 (2004)] focused on the development of a two-stage process for simulating flyover noise. The first stage entailed synthesizing the time histories at the flying source based on predictions of the source directivity. A second real-time rendering stage entailed propagation to a listener position on the ground, with binaural playback over headphones. More recently, loudspeaker based rendering was implemented for three-dimensional presentation in the NASA Langley Exterior Effects Room [J. Acoust. Soc. Am. 128, 2482 (2010); POMA 9, 015004 (2010)]. This paper discusses recent developments to the synthesis and rendering stages, including a new technique for sample-based synthesis of rotary wing sources, improvements to fan noise synthesis, and enhancements to ground plane simulation.
Comparison of near-field military jet aircraft noise with similarity spectra.
Authors: Neilsen Tracianne B. , Gee Kent L. , Wall Alan T. , James Michael M.
Published: July 2011

The jet mixing noise from high-performance military aircraft is broadband and, like other jets, appears to have two origins: the fine-scale turbulent structures (FSSs) close to the nozzle and the large-scale turbulent structures (LSSs) farther down the plume. The intense LSS noise dominates the radiation at inlet angles greater than 125 deg, and the more omnidirectional FSS noise is the dominant source of noise to the side and aft of the aircraft. An extensive set of measurements was taken of F-22 Raptor noise at different engine conditions in 2009. The F-22 noise is compared to the self-similarity spectra generally applied to describe the contributions of the LSS and FSS in jet noise [Tam and Zaman, AIAA J. 38, 592–599 (2000)]. For large inlet angles, the shapes of the noise spectra fit the LSS self-similarity spectra at low frequencies, but the self-similarity spectra roll off more steeply for frequencies above 1 kHz with the engine at military power and afterburner. Closer to the sideline, the FSS self-similarity spectra do not match the shape of the data spectra very well at high engine power. Possible reasons for these discrepancies are investigated. [Work sponsored by the Air Force Research Laboratory.]
Multipole representations of directional sources and derivation of directional starters for parabolic equation algorithms.
Authors: Vecherin Sergey N. , Wilson D. Keith , Ostashev Vladimir E.
Published: July 2011

Although many sources of outdoor sound (including aircraft, ground vehicles, machinery, and loud-speakers) are directional, most numerical methods for sound propagation are formulated for omnidirectional point sources. This paper describes a systematic approach to decomposing a directional source into its spherical harmonics and then representing each harmonic as a multipole (spatially compact collection of omnidirectional point sources). This effective source representation is useful for implementing directional sources in many numerical propagation methods. A new method is also derived for formulating directional starters in parabolic equation (PE) algorithms. The connections between multipole representations and directional starters are described with regard to the angular accuracy of the PE. It is shown that even horizontal multipoles can be appropriately represented with vertical starters, to a degree of accuracy consistent with the PE solution.
Array processing for direction of arrival of infrasound.
Authors: Costley R. Daniel , Frazier W. Garth , Dillion Kevin
Published: July 2011

Pipe arrays have conventionally been used to detect infrasound. The advantage of this approach is that the arrays have a large aperture over which wind noise can be averaged. In recent years, distributed arrays have been used for the same effect. In addition to reducing wind noise via spatial averaging, these arrays have the ability to process the individual signals from each sensor to estimate direction of arrival (DOA) of acoustic signals and, potentially, the direction of the wind flow. This is especially true for infrasound and low frequency acoustic sources of tactical interest, in the 1–100 Hz range. A frequency-wavenumber (F-K) processing technique has been applied to signals from rectangular infrasound arrays to estimate DOA. This approach will be discussed as well as the dependence of accuracy on signal-to-noise ratio.
In-situ calibration of infrasound array elements.
Authors: Gabrielson Thomas B.
Published: July 2011

A typical infrasound array element consists of an infrasonic pressure sensor connected to a multiple-pipe or porous-hose system for reduction of wind noise. While the frequency response of the sensor itself may be known, that response is modified by the wind-noise reduction system. One approach to measuring the frequency response of the complete system is to perform a comparison calibration using ambient noise and a co-located reference sensor with sufficiently low self-noise and well characterized frequency response. In the technique discussed here, the reference sensor is a virtual reference constructed by summing the outputs of two or three calibrated microphones; symmetric placement of the microphones places the phase center of the virtual reference at the geometric center of the pipe system. Proper combination of auto- and cross-spectral averages over a several-hour period produces an estimate of the response of the infrasound system relative to that of the virtual reference. Measured coherence and the consistency between the magnitude and the phase of the response provide quality checks on the process. This approach has been demonstrated at infrasound monitoring sites in Washington, Alaska, Manitoba, Austria, and Antarctica. [Funded by the US Army Space and Missile Defense Command.]
On the waveforms of infrasonic returns from the stratosphere.
Authors: Waxler Roger , Blom Phil , Talmadge Carrick L. , Assink Jelle
Published: July 2011

The stratosphere is said to end at the stratopause, a local sound speed maximum at about 50 or 60 km altitude. This maximum is typically about 320–330 m/s and is not large enough by itself to cause sound produced on the ground to be refracted back to the ground. There is generally a strong wind jet at the stratopause, the stratospheric jet, which provides sufficient additional refraction to return sound to the ground downwind from a source. In the absence of other effects, stratospheric returns have a universal form. The closest point of return is a caustic of the wave field at which there is a single arrival. Further out the signal splits into two arrivals: a higher-angle “fast” arrival and a lower-angle “slow” arrival. The fast arrival preserves the phase of the source while the slow arrival undergoes a 90 deg phase shift. Deviations from this behavior come predominantly from two sources: wind jets in the lower 15 km of the atmosphere and variations within the stratospheric jet. Illustrations from both data and models will be shown.
On the sensitivity of infrasound to the upper atmosphere.
Authors: Assink Jelle D. , Waxler Roger , Drob Doug
Published: July 2011

In comparison to the lower atmosphere where comprehensive global atmospheric specifications are commonplace, measuring the properties of the atmosphere above the stratosphere is an active area of scientific research. Here, we revisit the use of infrasound as a remote sensing technique for the upper atmosphere. Infrasonic signals from the Tungurahua volcano in Ecuador are used to investigate the behavior of the upper atmosphere. Depending on the atmospheric conditions, stratospheric, mesospheric, and thermospheric arrivals are observed during intervals of explosive volcanic activity. It is found that the travel times of the thermospheric arrivals exhibit a coherent variability with periods equal to those of the harmonics of the atmospheric tides. Theoretical predictions using atmospheric specifications show that the stratospheric arrivals are well predicted but that significant discrepancies exist for arrivals from higher altitudes. As such, these observations suggest a readily accessible means of passive atmospheric remote sensing that can be utilized in conjunction with other techniques as well as a-priori information to routinely measure and specify the state of the upper atmosphere.