Sonic Source Research Articles

Canine Model of Esophageal Injury and Atrial-Esophageal Fistula After Applications of Forward-Firing High-Intensity Focused Ultrasound and Side-Firing Unfocused Ultrasound in the Left Atrium and Inside the Pulmonary Vein

Left atrial-esophageal fistula is a serious and poorly understood complication of catheter ablation of atrial fibrillation. The purpose of this study was to (1) develop a canine model of esophageal injury and left atrial-esophageal fistula after applications of forward-firing high-intensity focused ultrasound (HIFU) and side-firing unfocused ultrasound (SFU); (2) examine the relationship to esophageal temperature (Eso-temp); and (3) study the evolution of injury/healing. Twenty dogs were studied. After transeptal puncture, HIFU catheter (ProRhythm Inc; 13 dogs) was positioned close to the esophagus, either outside (n=6) or inside (n=7) the inferior pulmonary vein (PV). In 7 other dogs, an SFU catheter was placed deep inside the PV, close to the esophagus. A balloon (20- to 25-mm diameter) with 7 thermocouples (2-mm separation) was positioned in the esophagus (Eso-balloon). Variable air filling of the Eso-balloon controlled the distance from the esophagus to the sonication source, pressing the esophagus against left atrium/PV. One to 9 (median, 5) HIFU (35 W) and 5 to 7 (median, 5) SFU (40 W) sonications were delivered for 40 seconds. Maximum luminal Eso-temp was closely related to HIFU Eso-balloon distance. For HIFU outside PV, Eso-temp >or=50 degrees C occurred only for HIFU Eso-balloon distance <or=2 mm. For HIFU/SFU inside the PV, Eso-temp was >or=50 degrees C, with HIFU Eso-balloon distance up to 6.8 mm. Endoscopy identified esophageal ulcer immediately after ablation in 11 of 13 HIFU dogs and 7 of 7 SFU dogs, all with Eso-temp >or=50 degrees C. Endoscopy at 2 weeks showed ulcer healing in 5 of 11 chronic dogs and ulcer size progression with relaxation of the lower esophageal sphincter and esophagitis in 6 dogs. Two dogs developed left atrial-esophageal fistula and died at 2 weeks. This model produces esophageal ulcer when Eso-temp is >or=50 degrees C. Eso-temp is higher with HIFU/SFU applications closer to the esophagus and with HIFU/SFU applications inside the PV. Ulcer progression and left atrial-esophageal fistula were associated with reflux esophagitis.

Unsteady Wing-Body Aerodynamics for Aeroelastic Applications at Mach One

Renewed interest in the sonic-box method is prompted by the possibility of near-sonic flights. For aeroelastic applications, the sonic-box methods, however, would be hindered by their drawbacks/confinements. They are based on a velocity-potential formulation, thus the wake domain must be modeled for planforms with swept trailing edges or for multiple lifting surfaces; their nonplanar lifting surface application has not been demonstrated, nor has its flutter applicability; their extensions for bodies remain unexplored. To this end, an unsteady sonic methodology employing sonic acceleration potential for multiple lifting surfaces (wings) and sonic source velocity potential for bodies has been developed. The present unsteady sonic method should be recognized as the sonic counterpart of our previous development of the unsteady subsonic and supersonic wing-body methods. It will be shown that unsteady sonic methodology employing sonic acceleration potential is an expedient method for flutter/aeroelastic applications for wing-body configurations in the sonic/near-sonic Mach number range.

Recomposition of the urban sonic environment

Acoustics‐related considerations are taken to be secondary in most of the design processes of public places. This fact always leads to an unpredictable noise and urban sonic environment around such spaces. Studies have shown the importance of the noise and the quality of the urban sonic environment in the social practice and in the daily use of public places. These places strongly mark the degree of dynamism of the urban structure of our cities and are often subjected to a very complex situation of noise nuisance. The main aim of the study is to introduce a source of noise that might have an effect of recomposing positively a deficient sonic environment of such places. This approach is also to try to restore the sound in its utilitarian and practical function and to articulate the perception of the spatial and temporal aspects of the public place. It could be an element of transforming urban noise into a peaceful soundscape. A fountain turned out to be that sonic source and it can be easily introduced in the urban environment around the public places. It is a sort of urban instrumentation used in order to recompose or requalify an urban noise environment.

The Affect of Selection in Digital Sound Art

The Affect of Selection in Digital Sound Art

Fast-field-cycling NMR study of magnetomechanically induced relaxation enhancement in ferrogelatine

We describe a field-cycling magnetic resonance experiment aimed to study the nuclear spinlattice relaxation in the simultaneous presence of an oscillating magnetic field and a magnetomechanically induced perturbation across the sample volume. The studied system is a gelatine doped with surfacted nanosize ferromagnetic particles. The spin system relaxes in coexistence with the magnetic interaction between the dopants and a weak external alternating magnetic field. Due to the interaction between the alternating field and the high magnetic moment of the dopants, a mechanical shaking of the particles becomes effective at low evolution fields. In this way, the particles act as local sonic sources, thus transmitting the vibrations to the gelic matrix where they are trapped. The impact produced on the molecular dynamics is observed through a magnetic resonance relaxation experiment. Saturation of the proton magnetization produced by the alternating magnetic field is also discussed. Results are compared with the direct effects produced by a pure sonic perturbation at the same frequency, introduced by coupling a piezoelectric transducer in direct contact with the sample.

超音波による気・液相界面の計測と挙動の観察

Meaurement of interface positions between liquid-liquid phases and liquid-gas phases are one of important problems in order to control chemical processes. We have developed ultra-sonic sensing methods for such interfaces in very corrosive chemicals. Two cells made of glass are used to evaluate sonic velocity and to confirm time difference between sonic source and interfaces. Each sound velocity in each phase of stratified layers agrees to that of pure liquid. Because sounds reflected from interfaces make complicated signals, we used a video observation to record sound signal and phenomena in the test cell and succeeded to recognize each reflected sound from each interface.

ELECTROPNEUMATIC TRANSDUCERS AS SECONDARY ACTUATORS FOR ACTIVE NOISE CONTROL, PART I: THEORETICAL ANALYSIS

A theoretical analysis is presented of an acoustic source which operates by the release of compressed air through an aperture, the area of which is made to vary with time. A distinction is made between sonic and subsonic compressed air sources (depending on the Mach number at the throat), and in both cases simple equations are derived that describe the acoustical characteristics of the device. The theory is also developed with a view to using the source as a secondary actuator in an active noise control system, and the pneumatic efficiency and linearity of compressed air sources are discussed. Although the sonic source has a high internal acoustic impedance and its output is almost linearly dependent on the aperture opening, it is shown to be very inefficient. The subsonic source can be much more efficient than the sonic one but the output is generally no longer a linear function of aperture opening. A simple method of linearizing such a source is discussed. A numerical comparison between compressed air sources and electrodynamic loudspeakers shows that the former offer a useful alternative for active noise control, especially when the secondary source has to act in an extreme environment. The subsonic compressed air source is particularly useful when efficiency is a major issue. Details and results of the experimental evaluation of a subsonic compressed air source built at the Laboratory of Acoustics of the Faculté Polytechnique de Mons (Belgium) are presented in companion paper (Part II).

Resonance Theory of Elastic Head Waves Propagating in a Solid Layer in Tight Contact With a Thick Solid Base

The boundary value problem of elastic wave propagation in the case of a plane solid layer I in tight contact with a thick solid base II with a monopole sonic source placed in layer I is treated analytically by the standing wave method. Solution in the form of contour integrals with the amplitudes in 2 x 2 matrix form are obtained. An inspection of the solution shows that it contains all well-known component waves except the head waves. Particular interest is put on these latter waves. Three kinds of head waves (P, S, and S1) are obtained. The S1 wave is newly predicted, which propagates with the shear wave velocity of the soft layer I. It may be considered as the candidate for the "late S wave" observed in earthquakes. The resonance frequencies of the three head waves are obtained, and the motion of the free surface is also described for the three cases.

The effect of ultrasonic frequency and intensity upon limiting currents at rotating disc and stationary electrodes

The limiting current from Fe(CN) 6 3− Fe(CN) 6 4− redox in dilute aqueous KCl at a platinum electrode appears to be little affected by the frequency of simultaneous ultrasonic irradiation in the range 20–800 kHz, and is not influenced by choice of bath or probe as sonic source, provided measurements are made at constant ultrasonic intensity. The limiting current is dependent on ultrasonic intensity at constant frequency. In contrast, the peak potential of the redox couple varies with ultrasonic frequency in the same range, but does not vary with ultrasonic intensity at constant frequency. Application of ultrasound to a rotating disc electrode provides an increase in limiting current across the frequency range, the magnitude of which varies with both concentration and rotation speed. The average maximum increase is some 1.5-fold which corresponds to an effective rotation rate of 100 000 rpm (1667Hz) for a silent solution in order to achieve the same transport rates. It is shown that changes in macroscopic temperature throughout the experiment are insufficient to cause the observed enhanced diffusion.

Form factor of a cylindrical sonic source and application in borehole acoustics

By introducing the concept of a form factor for a cylindrical sonic source, a new method is constructed for solving boundary value problems of the wave field produced by such sources when the solutions for a simple source is known, provided the boundary conditions are axisymmetrical and are linear and homogeneous in the potentials. The form factor is defined in cylindrical coordinates as a function F(k) of the wave number k. The analytic properties of F(k) are described. It is proved that F(k) can be obtained from the far-field approximation and is related to the directional factor through a simple transformation. The form factors of several simple-shaped sources are derived. The theory is applied to the case of a borehole to show that the effect of the form factor on the profile of the full wavetrain is prominent in certain cases.

A perceptual representation of sound for source separation.

Building machines that emulate the kinds of acoustic information processing that human beings perform effortlessly has proved unexpectedly difficult. The irresistible conclusion is that the human auditory system is extremely sophisticated in its adaptation to real-world sounds and uses an impressive array of features as cues to organization and interpretation. As more of these cues become known through psychoacoustical experiment, it becomes feasible to program computers functionally to mimic human perception of sound. Since the processing is so integrated and the roles of different features only partly understood, the best approach to simulating real listeners (including susceptibility to illusions) is to build as direct an analog of the actual processing chain as can be devised. Concentrating on the task of distinguishing and separating individual superimposed sonic sources, such as a singer and accompaniment, a perceptually sufficient invertible representation has been built that analyzes sound down to a relatively small number of ‘‘atoms.’’ Psychoacoustic rules of stream formation can then be applied to these atoms to simulate many aspects of human source separation. Examples will be shown and played.

Space surveillance apparatus with sound source and method of short-range space surveillance

A space surveillance apparatus includes at least one source of sonic radiation driven by a driver circuit as well as a processing or evaluation circuit. Upon movement of an object, or presence of a foreign object within a monitored space, the processing circuit triggers an alarm signal. Each sonic source defines the volume of its own monitored space, according to the equation: L=D.sup.2 /(4λ), wherein: L=Length of main direction of radiation of the monitored space; D=Diameter of diaphragm of sonic source; and λ=Wavelength of acoustic wave. The driver circuit drives the sonic source either in continuous mode, or in pulsed mode, and either at a constant wavelength or at a variable wavelength, i.e. in frequency modulation.

Characterization of Sonic Devices Used for Cleaning Fabric Filters

The values of the fundamental frequency and integrated output power of horns, or other sonic sources, do not provide adequate information to evaluate their potential effectiveness in baghouse applications, because these data give no indication as to the distribution of the sonic power as a function of frequency. The fundamental frequency denotes only the lowest possible mode of vibration. It is physically possible for a system to emit no sound at all at its fundamental frequency while producing intense sounds at higher frequencies. However, the use of a power-weighted mean frequency, and to a lesser extent, a geometric standard deviation provides a quantitative approach to the evaluation of horns for applications in cleaning fabric filters.

Simple electrostatic droplet source suitable for laser interaction

Small droplets for laser targets are continuously produced on the tip of a needle that emerges slightly from an insulating liquid. The method requires only a constant high-voltage source of 2-10 kV to polarize the needle, thus dispensing with the need for a capillary tube or pressure-controlled tank, or a sonic source. An optical system designed to collect the diffracted light is used for the detection of the droplets and laser triggering.

The Directionality Paradox of Jet Noise

The familiar noise contours for the axisymmetric jet exhibit the rather contradictory nature that at oblique downstream angles (where the noise is most intense) the spectral content is of lower frequency than that normal to the jet axis. The result is paradoxical if one imagines the source of the noise to be converted radiators of sound, Doppler-shifted upwards in frequency in the downstream direction. We postulate (1) that the sonic source region of the jet is bounded and (2) that in some time interval a countable number of independent local radiators are active. If Δt is selected as this time interval measured close to the axis, it is clear that at angles further from the axis one need not listen for as long a period of time to hear these same events. Hence, the frequencies of occurrence increase inversely with the cosine of the angle from the jet axis in the farfield. [This work has been supported by the Department of Transportation under Grant No. DOT-OS-00002.]

The Three-Dimensional Steady Radial Expansion of a Viscous Gas from a Sonic Source into a Vacuum

The three-dimensional steady radial expansion of a viscous, heat-conducting, compressible fluid from a spherical sonic source into a vacuum is analyzed using the Navier–Stokes equations as a basis. It is assumed that the model fluid is a perfect gas having constant specific heats, a constant Prandtl number of order unity, and viscosity coefficients varying as a power of the absolute temperature. Limiting forms for the flow variable solutions are studied for the Reynolds number based on the sonic source conditions, $1/\delta $, going to infinity and the Newtonian parameter, $\varepsilon $, both fixed and going to zero.For the case of the viscosity-temperature exponent, $\omega $, $1/2\leqq \omega < 1$, it is shown that the velocity as well as the pressure approach zero as the radial distance goes to infinity.The formulations of the distinct regions that span the domain extending from the sonic source to the vacuum are presented. For $\delta \to 0$, $\varepsilon $ fixed, there are three such regions; for $\...

Mapping the Earth with Elastic Wave Holography

Remote sensing of the earth has been carried on for many years by the use of transient elastic waves, as in the seismic method. With the advent of optical holography and the development of high-power sonic sources and electromechanical vibrators, it is now possible to map the subsurface structure of the earth with steady-state coherent waves. This is the process of earth holography, which provides a three-dimensional optical view of the earth's interior. The basic principles of wavefront reconstruction in optics are reviewed and their application to sonic and seismic wave holography discussed. The problems of scaling and field sampling are discussed in connection with the resolution of elastic wave systems. It is shown that the sampling density required is within practical field limits for adequate resolution. Experiments were carried out with a small water tank model using frequencies in the low MHz range and small metal objects. Data were recorded on magnetic tape and subsequently displayed. The resulting holograms and photographs of the reconstructed images are shown. Synthetic holograms and reconstructions are shown and the problems of recording and display are discussed. Possible extensions of this work to large area, deep mapping of the oceans and the earth are outlined.

Wind velocity measurements using sonic techniques1

A unique technique has been devised to measure wind speed and direction in space without any local sensor, artificial target, or any structure erected over the ground being necessary. Continuous recordings of wind speed and direction at a distance of 70 ft from a sonic source have been obtained by measuring the frequency shift of sonic waves scattered from a narrow beam generated by a powerful Levavasseur whistle at 10 kc. Two receivers in orthogonal directions with respect to the source provide continuous readings of the horizontal components of wind velocity. The series of over 300 sonic measurements on winds from 3 to 25 mph show average difference readings compared with an Aerovane anemometer not larger than ± 1.0 mph for speed nor ± 5.0° for direction, indicating a high degree of correlation between the sonic system and the more commonly used propeller type anemometers.