bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation and ultrasound-triggered bubble contrast agents based on superheated drops
Authors: Apfel Robert
Published: July 2012

Superheated drop compositions have been formulated for infusion in the body. Low doses of x rays or diagnostic ultrasound pulses are sufficient to nucleate the vaporization of these drops, producing bubbles that can serve as ultrasound contrast agents for imaging. Drugs can be carried in the drop material and can be released at a specific site where the radiation or ultrasound is focused. The current work describes the status of: (1) the optimization of the components that make up the composition, which include the superheated material, another liquid to adjust the degree of superheated, an encapsulant, and possibly a drug; (2) tests of the sensitivity of these drops to being triggered either by x rays or sufficiently intense pulses of ultrasound; (3) the analytic tools for characterizing the compositions and their triggering; and (4) the practical challenges to making this system suitable for clinical application.
Evolutionary strategy algorithm for a complete characterization of porous materials using a standing wave tube
Authors: Atalla Youssef , Panneton Raymond , Sgard Franck
Published: July 2012

A widely used model for describing the attenuation of an acoustical wave propagating in a rigid open-cell porous material is the Johnson–Champoux–Allard (JCA) model. This model is based on five macroscopic parameters describing the porous medium: flow resistivity, porosity, tortuosity, viscous and thermal characteristic lengths. Simultaneously with the development of direct methods for measuring these five parameters, defining and solving inverse problems based on an artificial intelligence approach appears to overcome some of the limitations of the direct methods. In this work, an application of the evolutionary strategy (ES) algorithm for the estimation of the five parameters of a porous material from simple acoustical measurements is presented. First, a number of numerical tests are performed and the results are used like a priori knowledge of how to set up an evolutionary algorithm to solve such a difficult problem in the shortest time. In the second step, the final setup of the evolutionary algorithm is applied for evaluation of the five parameters from experimental measurements. The method seems practical and promising since it is based on simple acoustical measurements and avoids using complicated and unreliable measurement setups.
Resonant acoustic measurement of the effective diffusion coefficient of gases through soil
Authors: Schuhmann Richard J. , Golden Matthew V. , Garrett Steven L.
Published: July 2012

Recent interest has developed within the environmental community in measuring the effective diffusion coefficient (De) of gases through soil. An electroacoustic system will be described that uses a plane-wave resonator and a phase-locked-loop automatic resonance frequency tracker. The gas analyzer is simple and can be built for about $100 from readily available plumbing parts and inexpensive transducers. A soil core is fitted into the top of a valved sample chamber and the resonator below is charged with a pure ‘‘tracer’’ gas (e.g., He, SF6), then the valve opened. The rate at which the tracer gas is replaced by air within the resonator is controlled by the soil’s De. The resonant frequency is maintained by a phase-locked-loop that compares the signal from an electret microphone with a square wave reference generated by the same monolithic function generator (XR 2206) that excited an electrodynamic loudspeaker with a sinusoidal current. The resonator temperature is monitored using a monolithic IC temperature sensor (AD 592) providing an output current of 1 μA/K. The mean molecular weight of the gas mixture in the resonator is directly determined in real-time from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. [Work supported by ONR.]
Bragg scattering by subsurface cracks and grooves
Authors: Danicki Eugene J.
Published: July 2012

Bragg scattering of bulk waves from shallow periodic grooves has been proven experimentally to be an effective method for generation of Rayleigh waves in solids. To study this phenomenon, a double layer of alternately positioned periodic cracks is investigated. The system looks like two aligned half-spaces with periodic grooves: cracks correspond to the main grooves’ faces; the mechanical connection of the grooves’ side faces makes the difference between these systems. A null-space expansion of the wave field is proposed that minimizes the resulting stress. The convenient BIS expansion method is applied in this extensive numerical investigation. For wide cracks, a mode can propagate in the system that resembles the Rayleigh wave because cracks make the substrate surface almost stress free. The efficiency of generation of this mode is studied as a function of crack period and width, the distance between crack layers (corresponding to the groove depth), and the angle of incidence of either shear or longitudinal waves. The results show that up to 25% of the incident bulk wave power can be transformed into surface waves in an optimal case with appropriate wave beamwidth. [Work supported by PAN-NIST Polish-US MS-Curie Joint Fund.]
Legislation concerning construction noise in Germany
Authors: Fischer-Sheikh Ali Eberhard , Irmer Volker K. P.
Published: July 2012

German legislation concerning construction noise started in 1965. It covers noise exposure in the neighborhood due to construction sites as well as noise emission from construction equipment. Noise exposure caused by construction sites may not exceed values specified in an administrative provision. These values differ for various types of residential areas and for different periods of the day. If they are, however, exceeded, the administration shall take the appropriate measures to limit the exposure. Noise emission from certain construction equipment is regulated by an ordinance; it contains noise limits that must be observed by the manufacturers placing equipment on the market and the obligation to label all equipment is specified with the sound power level guaranteed by the manufacturer. The limits depend on the type of equipment and its installed power. The Environmental Label (Blue Angel) is a voluntary product designation, it is one of the so-called soft instruments of environmental policy. The Blue Angel for construction equipment is awarded to machines that yield a noise emission 5–12 dB(A) less than noise limits of the ordinance mentioned above.
Moving frame acoustic holography and its possible applications in machine monitoring and diagnostics
Authors: Kim Yang-Hann , Park Soon-Hong
Published: July 2012

Moving frame acoustic holography has been successfully applied to predict sound pressure distribution on the surface of interest to us. It has been motivated to enlarge the aperture size of the hologram. In the meantime, however, a great deal of application has been found in what is related to making sound image with regard to time as well as frequency. The method is, in fact, analogous to a copy machine. We make the image of sound, instead of duplicating light image, which has to do with a copy machine. The theory [Y.-H. Park and S.-H. Kim, J. Acoust. Soc. Am. 104, 3179–3189 (1998)] shows that we can travel an array of microphones over the surface of which we want to have a sound/noise image. The theory also permits one to recover the sound image from the data obtained by the array microphone fixed on the ground. The sound image is the spatial characteristics of sound that will be observed by the microphone system attached to the sources. This paper reviews possible areas of applications for a train or subway, or a quality control system in a factory.
Vibration reduction characteristics of an isolated concrete test support
Authors: Khosrovani Hooshang
Published: July 2012

Some testing and research facilities require extremely low vibration background environments. Specially designed, isolated concrete supports are built to provide the required levels of isolation. The vibration isolation characteristics for an isolated concrete support have been measured and results are compared to predicted values.
Visual engineering environment based on interchangeable virtual instrument for acoustic pressure field
Authors: Lu Huancai
Published: July 2012

Architecture and kernel technology of a visual engineering environment for an acoustic pressure field is presented. The system software is constructed based on the hierarchy architecture of virtual instrument software and COM technique in order to realize the flexible reconfiguration of an acoustic pressure field measuring system. The attribute models of measuring channels and sensors are established for instrument’s and sensor’s interchangeability. The locking critical section technique is used for the security of multitask intercurrent process and share relation database. These kernel techniques make acoustic pressure field measuring system easily upgraded (e.g., the function and scale of the measuring system can be extended for different test tasks), instruments or sensors can be interchanged without modifying the software source codes. Therefore maintenance of the acoustic pressure field measuring system is greatly reduced and the lifecycle is prolonged. In this visual engineering environment, the measuring data of acoustic pressure field can be controlled in real-time and expressed in table, curve, bar chart, contour, and virtual instrument. Simultaneously the data can be transmitted through an ODBC interface to another computational environment (e.g., matlab) or Internet client for further analysis.
Detection of fatigue cracks by wavelet decomposition of the nonstationary narrow-band acoustical signal
Authors: Bouraou Nadejda I. , Marchuk Pavel I.
Published: July 2012

This paper presents new results of the signal processing of the nonstationary narrow-band acoustical signal for vibroacoustical diagnosis of air- craft engine blade fatigue cracks. The diagnosis method uses nonstationary vibratory excitation with a variable central frequency at the engine running start. The above-mentioned excitation is considered to be a linear-frequency-modulated signal with amplitude modulation by a stationary random process. The cracked blade is considered to be piecewise-linear system. Assuming these preconditions, the nonstationary narrow-band acoustical signal, radiated by the blade, is simulated and processed by using the wavelet decomposition technique. Fault detection is carried out at the approximation of the last (fifth) level of decomposition. The influence of the crack size increasing on the considered level approximation is investigated.
Direct measurement of the glottal volume velocity waveform in an in vivo canine model
Authors: Verneuil Andrew , Kreiman Jody , Gerratt Bruce R. , Dhir Vijay , Berke Gerald
Published: July 2012

Phonation occurs when the potential pressure energy provided by the lungs is translated into the kinetic energy of a glottal air pulse by the vibrating vocal folds. The primary acoustic source energy is described by the amount of air passing the glottis (volume) and the instantaneous speed at which it is moving (velocity). Indirect methods of acoustic analysis have provided estimates of the volume-velocity waveform. This study provides direct measurements by applying a constant temperature anemometer and videostroboscopic glottic analysis in an in vivo canine model. The velocity profile across the glottis and glottal area were measured in the anterior, middle and posterior glottis. These measurements were then temporally synchronized and combined to create a volume-velocity waveform of the acoustic source. Consistent with previous studies, velocity waveforms were double peaked across the glottis and were usually greatest anteriorly. Significant contributions to the volume-velocity waveform were made by the anterior and middle portions of the vibrating vocal folds, while the posterior glottis had less contribution. Inertial delays and flow reversals were demonstrated during the closed phase of phonation. Understanding the measured volume-velocity waveform provides more insight into the acoustic source spectrum and its role in phonation.
Flow visualization in a model of the glottis with a symmetric and oblique angle
Authors: Shinwari Daoud , Scherer Ronald C. , Afjey Abdollah A. , DeWitt Kenneth
Published: July 2012

Modeling the human larynx can provide insights into the nature of flow within the glottis. This study reports intraglottal pressure profiles and flow visualization for a symmetric and an oblique glottis with a glottal angle of 10 deg divergence. For the oblique case, the glottis slanted at an angle of 15 deg. A Plexiglas model of the larynx was used. Each vocal fold had at least 11 pressure taps. The minimal glottal diameter was held constant at 0.04 cm. Each case was subjected to steady airflow corresponding to transglottal pressure drops of 3, 5, 10, and 15 cm H2O. Pressure profile results showed that pressures were different on the two sides of the glottis; these data were strongly supported by an earlier study using a different model. Flow visualization in all cases showed that flow separated from one side of the glottis and remained attached to the other. For the oblique case, the separation point on the divergent wall moved upstream in the glottis with greater flows. The laminar core of the skewed jets decreased in length with higher flows. The jet caused asymmetric circulating regions downstream of the glottis in the reservoir section. [Work supported by NIH.]
Utterance–final voice quality variations: Their perceptual structure and acoustic correlates
Authors: Herman Rebecca
Published: July 2012

Voice quality variations can be used to mark prosodic and discourse boundaries in running speech. In order to quantify acoustic events in the signal during the production of these voice qualities, it is necessary to first discover their perceptual structure. The perceptual structure can then inform the acoustic analysis and help to find perceptually salient acoustic correlates. In this study, a perceptual experiment was run in which the stimuli were single words spoken by multiple talkers, which had all been extracted from the ends of utterances. Pairs of stimuli were given similarity ratings by listeners, and the similarity ratings were used in a multidimensional scaling analysis. The dimensions found in the multidimensional scaling analysis were interpreted using acoustic analysis. The voice qualities of the female voices in this study were found to have a primary perceptual split which was interpretable acoustically as laryngealized versus nonlaryngealized, but the voice qualities found in the male voices did not group into categories, and the perceptual dimensions were not as clearly interpretable in acoustic terms.
Individual differences in speech production: Voice-onset-time
Authors: Allen J. Sean , Miller Joanne L.
Published: July 2012

As part of an ongoing study of talker-specific speech processing, we sought to document the existence of individual talker differences in voice-onset-time (VOT). Four female and four male talkers, all native speakers of American English, were asked to produce 30 repetitions each of 18 different words beginning with /p/, /t/, or /k/. Words were displayed visually on a computer monitor one at a time in a randomized order at a constant presentation rate, and talkers were asked to produce the words at a comfortable speaking rate. The VOT and duration of each spoken word were measured. The eight talkers showed substantial individual variation in speaking rate (as measured by word duration) and, as would be expected, slower speaking rates were associated with longer VOT values. In order to determine whether there were individual differences in VOT beyond those associated with speaking rate, we conducted analyses that controlled for speaking rate on a word-by-word basis. These analyses revealed cases of consistent individual differences in VOT. We are currently examining whether the structure of listeners’ perceptual voicing categories reflects such individual talker differences. [Work supported by NIH/NIDCD.]
At-sea measurements of sound penetration into sediments using a buried vertical synthetic array
Authors: Simpson Harry J. , Houston Brian H. , Berdoz Alian R. , Frank Philip A. , Liskey Steve W. , Stanic J. S. , Frederickson Carl K.
Published: July 2012

At-sea measurements were conducted to understand the propagation of sound into sediments. These investigations used a new, buried vertical synthetic array system developed and built at the Naval Research Laboratory. The design of this at-sea system is based on a system developed for laboratory experiments that utilized a two-dimensional synthetic array technique [J. Acoust. Soc. Am. 107 (2000)]. For the measurements reported here, the hydrophone was water-jetted into the sediment to a depth of 2 m. Once buried, the hydrophone was mounted to a vertical robotics stage that pulled the hydrophone up in 1-cm increments. A spherical source, positioned 50 cm above the interface, was used to ensonify the sediment. The ensonification angle was varied by changing the horizontal distance of the source from the insertion point. In this manner, several measurements were made with ensonification angles above and below the critical angle. In addition, the enhancement of sound penetration due to interface roughness was investigated. This new system, along with the results of the measurements, will be discussed. [Work supported by ONR.]
Assessing 3D volume inhomogeneity using a noninvasive diver-deployed resistivity array
Authors: Jackson Peter D. , Gunn David A. , Briggs Kevin B.
Published: July 2012

A noninvasive electrical resistivity array imaging system (RAIS) has been developed to measure sediment volume inhomogeneities in three dimensions. Novel measurements of electrical fields, due to controlled galvanic current-flow, have been inverted into electrical resistivities, in three dimensions beneath the seafloor. The limitations of conventional 3D resistivity inversions are explored, and additional a priori constraints are shown to significantly improve performance in the seafloor environment. From these 3D resistivity distributions, correlation lengths in x, y, and z dimensions are calculated to support the modeling of acoustic scattering from the seafloor. Examples obtained during November 1999 in the Gulf of Mexico for the ONR High-Frequency Sound Interaction in Ocean Sediments (SAX99) experiment are described. New technology has reduced the acquisition time for a 3D dataset of 3840 measurements from approximately 2 h to 90 s, enabling a suite of locations to be investigated during a single dive. Converting to formation factors and combining with porosity/density data enabled to tortuosity of the electrical current-paths to become a pore morphology descriptor. Formation factors were found in the range 2 to 5, being consistent with substantial bioturbation in sandy sediments, with heterogeneities identified up to 100 mm.
Using one or two hydrophones for marine animal surveys
Authors: Cato Douglas H. , McCauley Robert D.
Published: July 2012

Acoustic surveying of marine animals requires the ability to localize the sources or at least determine their distances, if the density of the animals is to be determined. Precisely placed multiple-element arrays will provide this information, but there are logistically simple techniques using one or two hydrophones that are effective under certain conditions. If the propagation conditions are known, the differences in the times of arrival and the received levels on two hydrophones provide the distance of the source and the source level, for sources significantly closer to one hydrophone than to the other. The positions of the hydrophones do not need to be known, but if they are, the sources can be localized with left–right ambiguity. An example is the use of sonobuoys deployed from a ship in transit. One hydrophone is sufficient if the direct and surface reflected paths can be separated, since the surface image can be used in place of the second hydrophone. Some examples of this applied to movement of fish sources will be presented. Complex propagation causes difficulties but these may also be exploited to improve the estimates.
Localizing marine animals and how marine animals might localize sound
Authors: D’Spain Gerald L. , Lepper Paul A.
Published: July 2012

We can locate vocalizing marine animals, and the animals themselves might locate sound sources, in one of several ways. Time-of-arrival (phase) differences and amplitude differences of a single arrival between spatially separated ‘‘ears’’ are well-known techniques. However, they become ineffective in multipath environments and as the frequency of the sound and/or spatial separation between ears decreases. Another approach is to sense properties of the acoustic field in addition to acoustic pressure. This approach, based on a simple Taylor series expansion of the field and ‘‘f=ma,’’ apparently is exploited by fish, making them biological equivalents of DIFAR sonobuoys. However, do they also measure acoustic strain rate? An additional method, used by humans, is to take advantage of time-of-arrival (phase) differences between multipath arrivals. The information on source location contained in the resulting interference patterns can be understood in terms of waveguide invariants. These speculations will be illustrated with numerical simulations and actual ocean acousic data. [Work supported by ONR.]
Energetics of dislocations in ocean acoustic fields
Authors: D’Spain Gerald L. , Williams Duncan P. , Kuperman William A.
Published: July 2012

Dislocations are places in the acoustic field where the amplitude goes to zero and the total field phase becomes undetermined [Nye and Berry (1974)]. The positions of these dislocations are sensitive indicators of changes in the ocean environment. Expressions for the acoustic potential and kinetic energy densities and active and reactive vector acoustic intensities are derived for a single-tone sound field. These expressions are then applied to infrasonic ocean acoustic data collected by the Marine Physical Lab’s set of freely drifting Swallow floats to help identify dislocations in the underwater acoustic pressure and the component particle velocity fields. Likely dislocation positions were identified during cw source tows at 7, 10, and 16 Hz during the 1990 NATIVE 1 experiment near the Blake Plateau in the northwest Atlantic Ocean. The neighborhoods of dislocations, as well as near other amplitude minima, are regions where a significant acoustic energy flow occurs. The relationship between dislocations and polarization of the acoustic particle motion also is discussed. [Work supported by ONR.]
Matched field inversion with a moving source in a shallow-water environment
Authors: Viechnicki John , Chapman Ross
Published: July 2012

Geoacoustic inversion based on matched field processing (MFP) is examined for shallow-water, low-frequency environments. Specific interest lies with resolving geoacoustic parameters from cw tones projected from a moving source. Data obtained using vertical line arrays (VLA) are available from both the 1996 Haro Strait PRIMER Experiment (HSX) and the Santa Barbara Channel Experiment (SBCX) of 1998. The environmental complexity associated with these experiments, namely, strong range-dependent bathymetry and current flow, is typical to littoral environments in general and must be appropriately addressed. Parabolic equation modeling is used as it provides range-dependent results. The VLA receiver configuration is described as a catenary which is typical of bottom-anchored arrays drifting in uniform current flow. Both SBCX and HSX are useful for benchmarking geoacoustic inversion techniques since results from other techniques are available. Estimation of bottom properties is discussed as a function of propagation range, ship track with respect to receiver position, and general bathymetric features. Results for both tangential and radial tracks are presented. [Work supported by ONR.]
Frequency dependent transmission loss related to modal properties in layered nonlinear internal wave environments
Authors: Frank Scott , Siegmann William L. , Badiey Mohsen , Mu Yongke , Lynch James F.
Published: July 2012

Broadband data were taken during the SWARM 95 experiment from airgun and linear frequency modulated sources while nonlinear internal waves were crossing two different propagation tracks. In a previous study, the geotime behavior of the depth-averaged received intensity was examined, and amplitude modulations were associated with the passage of internal waves. Additionally, a time-frequency analysis of the data exhibited periodic changes in the modal structure of the signals. Though some discrepancies occurred, both of these effects were observed in parabolic equation simulations of the SWARM environment. To address the discrepancies in received intensity levels, various physical mechanisms will be investigated, for example geoacoustic attenuation and ocean thermocline variability. Effects on the time-frequency representations of signals passing through internal wave packets will be documented and categorized. To understand features of frequency dependent transmission loss, relationships between the eigenvalues and the variable layer structure of the waveguide will be developed and applied to both measurements and simulations. Such relationships will aid in extracting the amplitude, width, and azimuthal propagation angle of nonlinear internal waves from broadband acoustic data. [Work supported by ONR.]
Theoretical predictions of ultrasonic fields, temperature response, and lesion dynamics in biological tissue for the purpose of noninvasive disease treatment
Authors: Curra Francesco P. , Mourad Pierre D. , Kargl Steven G. , Crum Lawrence A. , Khokhlova Vera A.
Published: July 2012

Ultrasound has been used for decades as a means for noninvasive treatment of diseases. Low-intensity ultrasound is routinely applied in physical therapy for muscular and neurological related illnesses. In contrast, high-intensity focused ultrasound (HIFU) is used to induce coagulative necrosis of tissue for cancer treatment or hemostasis. Our efforts concern the latter. Predictions of ultrasound fields, temperature response, and lesion dynamics are obtained by a model which accounts for nonlinear sound propagation in inhomogeneous media, an arbitrary frequency power law for acoustic attenuation, and temperature time history [J. Acoust. Soc. Am. 107, No. 5, Pt. 2 (2000)]. The model is expanded from its previous version to include attenuation and sound speed dependence on temperature levels and also to consider generation of gas bubbles within the tissue. Results are presented in terms of treatment strategies that provide maximum energy transfer for coagulating the targeted tissue while minimizing damage to the surrounding area.
Behavior of ultrasound contrast agents near the fragmentation threshold
Authors: Chen Wen-Shiang , Matula Thomas J. , Crum Lawrence A.
Published: July 2012

Understanding the destruction process of ultrasound contrast agents is important in therapeutic ultrasound applications (such as ultrasound-enhanced drug delivery), as well as in certain imaging applications (such as ‘‘flash echo’’ imaging of the myocardium). In the destruction of OptisonTM microbubbles, our observations suggest that there are two pressure thresholds: a lower threshold which leads to shell rupture and the production of daughter (derivative) bubbles, and a higher threshold leading to the onset of the inertial cavitation (IC) activity. Slightly above the shell-disruption (SD) threshold, the acoustic scattering signal decreases, presumably due in part to the partial dissolution of the derivative bubbles. The extent of the quiescent region, the IC pressure threshold, and the strength of the subsequent cavitation activity are all highly dependent on the acoustic pulse parameters. It is found that for pressure amplitudes in excess of the IC threshold, a longer pulse length or a higher pressure level will decrease the duration of this quiescent period. By controlling the bubbles’ response through fine-tuning the acoustic parameters near the SD and IC threshold, one could design an ultrasound system which would optimize the desirable effects of contrast agents for imaging and therapy applications. [Work supported in part by ONR and WTC.]
Analysis of deformation process for cell model including a gas bubble by shock waves
Authors: Tamagawa Masaaki , Yamanoi Ichiroh , Matsumoto Atsuhi
Published: July 2012

This paper describes the analysis of deformation process for cell model including a gas bubble by shock waves and flow induced by propagating underwater shock waves, in order to study the mechanism and high efficiency of destruction of cells and microcapsules by shock waves and bubbles, such as for drug delivery system (DDS) and for bioprocesses to make energy and for environmental protection. For this analysis, the cells are modeled as liquid droplet including a gas bubble in water. By computation, using the ALE (arbitrary Lagrangian–Eulerian) method, the coupling oscillation is analyzed for particle velocity and pressure wave through the cell. The results show that the effects of the acoustic impedance of the fluid media in water is large for the deformation process and the effects of deformation of droplet boundary is also large for deformation process for a gas bubble inside the cell and for microjet flow by a collapsing bubble.
Study of the mechanism of fragmentation of a microbubble exposed to ultrasound using a high-speed observation system
Authors: Kudo Nobuki , Miyaoka Takehiro , Kuribayashi Kaori , Yamamoto Katsuyuki , Natori Michiya
Published: July 2012

In this study, we observed the dynamic behaviors of microbubbles exposed to ultrasound using a high-speed camera (Ultranac, Nac, Japan). Although the maximum frame rate of the high-speed camera used in this study is 20 million frames/s, the possible frame rate was limited to 6 million frames/s because the high optical magnification of the observation system resulted in a shortage of light exposure to the camera. Behaviors of albumin-shelled microbubbles of 10–60 microns in diameter were clearly observed as in 24-frame sequential high-speed photographs at the maximum optical magnification of 85×. Several typical phenomena of bubble behavior, such as deformation and rupture of the bubble shell, anisotropic contraction of a microbubble and generation of a small stream, and fragmentation of a bubble by the small stream, were observed. From those observation results, it was concluded that the small stream generated by anisotropic contraction of a microbubble exposed to ultrasound causes fragmentation of the bubble in the contraction phase. [This research was partially supported by a grant-in-aid for scientific research from the Ministry of Education, Science, Sports and Culture, Japan.]
Statistical characterization of high-frequency ultrasonic scattering from human skin in vivo
Authors: Raju Balasundar , Srinivasan Mandayam
Published: July 2012

High-frequency ultrasound backscatter signals from forearm and fingertip skin in vivo of 20 normal human volunteers were analyzed in terms of their envelope statistics. Data obtained from several focal zones by axially translating a focused transducer were gated (100 ns) and Fourier transformed to compute magnitude of envelope at the center frequency of 30 MHz. It was found that the envelope histograms and SNR were significantly affected by the presence of occasional peaks that were unlikely to be from the background tissue. Hence a new parameter, the ratio of median to interquartile range (MQR) was used to evaluate its potential for tissue characterization. For all focal zone depths (up to 3 mm for forearm and 1.95 mm for fingertip), the MSR value was less than the Rayleigh limit of 1.30, indicating the presence of non-Rayleigh statistics. Significant differences in MSR were found between tissues close to the surface (0.3 mm) at the fingertip and forearm (0.67±0.16 vs 0.97±0.13 at 30 MHz, mean±SD values are among subjects), which could correspond to anatomical differences at these locations, namely the increased thickness of the stratum corneum at the fingertip. These results indicate that non-Rayleigh statistics might aid in discriminating different skin tissues.
Surface acoustic wave velocity in thin biotissue
Authors: Miyasaka Chiaki , Tittmann Bernhard
Published: July 2012

We report a technique to characterize small portions on the order of a few microns of a biological tissue. The heart muscle was selected for specimen as an example of the soft material. The heart muscle was cut by a microtome and coated on a substrate. The thickness of the specimen was about 3 μm. Fused quartz was used as a substrate because its elastic properties are known and stable. A spherical lens was used to determine the position for the measurement. A cylindrical lens was used to measure velocities of the SAW waves within the specimen. 400 MHz was used for both imaging and measurement. The generation of the SAW waves was simulated by numerical calculations based on the wave propagation theory for layered media. As a result, the variation of the velocities representing the anisotropy of elastic properties was obtained and found to be about 7%.
Calibration of electret microphone cartridges for application in a multichannel acoustic array
Authors: Zuckerwar Allan J. , Humphreys William M. , Bartram Scott M.
Published: July 2012

Electret condenser microphone cartridges, having the advantages of small size, low cost, few lead wires, low output impedance, and acoustic specifications comparable to those of air condenser microphones, are well suited for application in multichannel acoustic arrays. Amplitude and phase calibration of electret cartridges by two methods is described. In the first, a test cartridge, reference microphone, and driver are inserted into a coupler, whereby the calibration takes place by a comparison method. In the second method, the calibration is performed in a commercial acoustic calibrator (B&K type 4226), which was modified by the manufacturer to permit the phase calibration. Further, a special adapter was fabricated to seat the cartridge at the proper position in the calibrator coupler. Amplitude and phase calibrations of 80 electret microphones were performed. The calibrated microphone cartridges were flush-mounted in an 80-channel array to measure dynamic surface pressures. The array was installed in a backward-facing step model and tested in a low-speed wind tunnel. An associated data acquisition system performed conditioning and digitization of the signals from each of the microphones. Preliminary results using the array to characterize the pressure distribution in the separated flow region downstream of the step will be reported.
The acoustics of the Asian free reed mouth organs
Authors: Cottingham James P.
Published: July 2012

Mouth-blown instruments using a free reed coupled to a pipe resonator have a long history in China, Japan, and throughout Southeast Asia. The sheng, khaen, and bawu have been studied experimentally and theoretically as typical representatives of this family of instruments. Acoustical measurements made include studies of reed vibration and impedance measurements of the pipes. Particular attention has been paid to the coupling of the reed vibration with the pipe resonator. The sheng employs a free reed at one end of a closed tube with a conical-cylindrical cross section. The khaen employs an open tube of effective length L, with the reed located at approximately L/4. The bawu is a closed cylindrical pipe with the free reed at one end, in which the effective acoustical length is varied by the use of tone holes. The playing frequency of each pipe of the sheng or the khaen is typically slightly above both the resonant frequency of the pipe and the natural frequency of the reed. In the bawu, on the other hand, both the pipe resonance and sounding frequency are normally well above the natural reed frequency, resulting in a striking difference in tone quality.
The Klais organ in Kyoto: A comparison of the acoustics of the Japanese organ stops to the traditional Japanese instruments
Authors: Braasch Jonas , Ahrens Christian
Published: July 2012

The Klais organ in Kyoto is unique among organs of the world in having a section with Japanese organ stops. Although common organ stops are sometimes named shakuhachi in Japan, the Klais organ is the only one that has, besides a French and a German section, a Japanese section containing four specially designed stops imitating the Japanese instruments: shakuhachi, shinobue, sho, and hichiriki. While the shakuhachi and shinobue stops use flue pipes, free-reed pipes are used for the sho and the hichiriki. Sound recordings of single tones were made of these Japanese stops and analyzed regarding the sound spectra and the attack transients, as well as the variation of the fundamental frequency during the attack transient. For comparison, sound recordings of traditional instruments were made at the Geijutsu Deigaku University of Tokyo. The results show that the sound characteristics of the traditional instruments could be imitated quite well. The free-reed pipes work well not only to imitate the free-reed instrument sho, but also to imitate the double-reed hichiriki. This organ is a good example in which the long-neglected free-reed stops are more suitable than the commonly used beating reed stops. [Work supported by DFG.]
Two-dimensional instability study of a thermoacoustic prime-mover
Authors: Delbende Ivan
Published: July 2012

A numerical model aimed at investigating the development of instability in a thermoacoustic prime-mover is presented. It is based on a discretization of the two-dimensional compressible Navier–Stokes equations, and does not rest on the plane pressure wave assumption. The computational domain is made of a single stack interplate space extended up to both resonator ends. The working gas is assumed to be initially at rest, and a longitudinal temperature gradient is enforced. The linear instability properties of the system are then given by the eigenmodes of the discretized evolution operator linearized in the vicinity of the above basic state. Temporal growth rate and oscillation frequency are thus obtained for all thermoacoustic modes, and the prime-mover instability onset is determined as a function of the various parameters (mainly temperature gradient magnitude and mean pressure). As far as linear instability is concerned, this formulation is attractive, since it avoids any direct numerical simulation and any problem involved by the presence of two very different time scales.
Experimental instability study in a thermoacoustic prime-mover
Authors: Bretagne Emmanuel , Delbende Ivan , François Maurice-Xavier
Published: July 2012

An experimental linear stability study of a thermoacoustic prime-mover is performed for different values of the mean pressure between 0.5 and 10 bars. The damping rate is carefully obtained as a function of the temperature gradient |∇T| enforced along the stack, up to the instability onset at |∇T|c. These results are then confronted with the predictions of a numerical model based on Rotts’ theory used with complex frequencies, in which the prime-mover is seen as a feedback loop in the electrical analogy. The experimental results are found to reasonably comply with Rott’s theory as soon as the mean pressure exceeds 2 bars. Below this value substantial discrepancies are found, as confirmed by the work of Yazaki. Above the instability onset, the saturated wave amplitude is measured as a function of |∇T|−|∇T|c for fixed pressure. The bifurcation to the nonlinear saturated wave has been tentatively determined as subcritical, although thermal inertia effects make it look supercritical.
Performance improvements for the solar powered, thermoacoustically driven, thermoacoustic refrigerator
Authors: Adeff Jay A. , Hofler Thomas J.
Published: July 2012

The world’s first completely solar powered, thermoacoustically driven, thermoacoustic refrigerator has been improved with increased cooling power and higher efficiency. A larger 24-in.-diam Fresnel lens provides increased heat power to focus sunlight at 550°C onto the hot end of a 1-in. reticulated vitreous carbon prime mover stack. The high-intensity sound waves produced by the prime mover are used to power a thermoacoustic refrigerator. The cooling power has been substantially improved and the temperature span has been increased from 18 to 30°C with the cold end at 0°C.
Thermoviscous functions of wire mesh and RVC stacks
Authors: Muehleisen Ralph T. , Beamer C. Walter
Published: July 2012

Thermoacoustic stacks made of stacked wire-mesh elements or reticulated vitreous carbon (RVC) are becoming popular because of their performance, cost, and ease of construction. The thermoviscous Rott functions fν and fκ [related to the porous media function F(λ)] have been measured for wire mesh and RVC stacks. The thermoviscous functions were determined from measurements of the characteristic impedance and propagating wave number of the stacks. The measurements were then used to develop empirical models for the stacks. The measurement technique, measurement results, and emprical models are presented. [Work supported by the Office of Naval Research.]
Predicted and measured structural intensities in the lexan and aluminum INCE standard ribbed panels
Authors: Hambric Stephen , Szwerc Richard , Chang Henry
Published: July 2012

Comparisons of predicted and measured structural intensities in vibrating lexan and aluminum ribbed panels are made. Structural intensities are predicted using finite-element models composed of plates and beams and the McPOW (mechanical power) software. Wave decomposition methods were used to estimate bending wave intensities by postprocessing velocity fields on the lexan and aluminum ribbed panels measured using a scanning laser Doppler vibrometer (SLDV). Each panel was driven at one rib with a point drive and suspended with soft springs to simulate free boundary conditions. Intensity fields are compared for each panel’s (7,2) mode. The intensity fields are normalized by the power input to the panels by the point drive. The predicted intensity fields for both panels, when normalized by the power input, are nearly identical. The measured intensity fields are similar to each other and to the predicted fields, but show some differences. The discrepancies are due to measurement uncertainties and manufacturing differences. The results help mutually validate the prediction and measurement approaches.
Alvin M. Liberman and the development of scientists: Chairman’s introduction
Authors: Whalen D. H.
Published: July 2012

Alvin M. Liberman contributed to the theoretical field of speech for half a century, and was still contributing at the time of his death in January of 2000. The papers in this session will celebrate some of those contributions, but will also highlight another aspect of his career that made him a powerful force: He brought out the best scientific effort of all those around him—his students, his colleagues, his children, and (even perhaps especially) his critics. Liberman’s influence will continue for the lifetimes of those who knew him, and no doubt longer through his impressive body of work.
Alvin Liberman, infant research, and the speech module
Authors: Eimas Peter D. , Miller Joanne L.
Published: July 2012

In 1957, Alvin Liberman offered a highly controversial statement based on the experimental work at Haskins Laboratories, known as ‘‘the motor theory of speech perception.’’ Over time, the theory evolved to presume that the mechanisms underlying speech processing were biologically determined and specialized for the perception and production of speech. Speech perception was in effect not an auditory process, at least beyond the initial reception of speech, but rather part of a species-specific processing system that made language possible. We consider this view in light of selected aspects of our research on infant speech perception, which was driven in large part by the work of Liberman and his associates. We believe that the evidence in its entirety supports Liberman’s idea of a species-specific processor or module that permits the acquisition and use of language, including much of the relatively early processing of speech.
A locally conformal method for modeling rigid boundaries in the FDTD method
Authors: Schneider John B. , Tolan Julius G.
Published: July 2012

The finite-difference time-domain (FDTD) method is a numerical technique that can be used to solve a wide variety of problems via time-domain simulations. A low-cost method has previously been presented for accurately modeling continuously varying pressure-release surfaces [Schneider et al., J. Acoust. Soc. Am. 104, 3219–3226 (1998)]. The overall simplicity of the FDTD method was preserved by requiring modifications only in the vicinity of the pressure-release boundary. Thus, the implementation of such things as sources or absorbing boundary conditions can be left unchanged. This paper describes a technique, which is similar in spirit but different in detail, that permits accurate modeling of continuously varying rigid boundaries. The technique is simple to implement, has low computational cost, and provides substantial improvements over a traditional ‘‘staircased’’ representation of the boundary. Accuracy is established by comparing results to those for canonical scatterers. [Work supported by ONR.]
Using time-variant electronic architecture to improve outdoor acoustics
Authors: Barbar Steve
Published: July 2012

The outdoor environment offers little of the acoustical support provided by the traditional architecture and surface treatments found in good concert halls or opera houses. While these treatments can be used as part of a shell or enclosure where the musicians perform, incorporating architectural treatments that improve listening enjoyment for the audience, or return energy for the musicians, is much more difficult. Sound reinforcement systems used for classical music or opera outdoors can assist in improving the impact of the direct sound when used carefully. Such systems, however, can do little to improve the sense of envelopment and warmth that are an important part of the listening experience for this type of performance. Recent developments in technology have produced a system that uses time variance to reduce the effects of acoustic feedback. These systems have a significant advantage in gain before coloration over previous methods (typically 12 dB or more). When used outdoors, this system provides reflected and reverberant energy for both musicians and the audience. Additionally, this energy can help to mask noise intrusion from sounds outside the designated seating area. The following is what we have determined to be important parameters for the successful implementation of such a system.
Hot topics in acoustical oceanography
Authors: Lynch James F.
Published: July 2012

Acoustics continues to play an ever-increasing role as a means of exploring the ocean. In every area of oceanography, acoustic techniques are being used to make measurements that would have been considered science fiction only a few scant years ago. In this lecture, we will show some of the recent, sometimes startling advances that have been made in oceanography using acoustics. We will also endeavor to put the acoustics measurements in the context of other types of measurements that are made. Starting with physical oceanography, we will look at the advances that have been made, going from the largest (gyre) scales to the smallest (microscopic turbulence) oceanographic scales. We will then turn to marine geology, and examine how various acoustic techniques both map the structure of the marine sediments and also help us understand the formation of sedimentary structures. Finally, we will examine marine biology, where acoustic techniques are helping us quantify the abundance of marine life and, at a more basic level, understand marine ecosystems.