Amplitude Sound Waves Research Articles

Imaging of the heart with phonocardiography

Abstract This paper focuses on techniques of phonocardiographic image registration. Simultaneous measurements of sound wave amplitudes from above the chest of a healthy person were performed by means of piezoelectric microphones. The location of the source of sound waves can be determined by implementing the size of the amplitudes. Sound source changes its position in time and moves the wheel tracks covering the entire heart or accumulate in some places. A comparison of the results of heart auscultation with an image received by echocardiography was possible due to the fact that the collected phonocardiographic measurements and echocardiographic examination were obtained with ECG sampling. The occurrence of the specific events from the heart auscultation was attributed to their genesis mechanism.

Distance Characteristics of Sound Wave Attenuation in ER Fluids

Electrorheological fluids(ER fluid) as an electrically controllable acoustic medium has been proved by experimental studies. In this paper,the sound attenuation in ER fluid at different propagation distances was experimentally studied. The results show that sound attenuation of ER fluid could be adjusted by the particle concentration of ER fluid and the intensity of electric field. Amplitude of sound wave in ER fluid increases with the increasing of particle concentration and field intensity; on the other hand, the attenuation of sound wave decreases with the increasing of propagation distance, as well as the particle concentration and field intensity. The experimental results indicate that the solidification effect of ER fluid is beneficial to the propagation of sound wave. DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.1994

Attenuation Characteristics of Sound Wave in Silicon Dioxide ER Fluid

The sound attenuation in ER fluid was experimentally studied. The results show that sound attenuation of ER fluid could be adjusted by the particle concentration of ER fluid and the intensity of electric field. Amplitude of sound wave in ER fluid increases with the increasing of particle concentration and field intensity; on the other hand, the attenuation of sound wave decreases with the increasing of propagation distance, as well as the particle concentration and field intensity. The experimental results indicate that the solidification effect of ER fluid is beneficial to the propagation of sound wave.

Body surface scanner for the abdominal sound speed tomographic imaging

The ultrasound tomography has been studied for the reconstruction of the abdominal sound speed image to measure the visceral fat area. The method is based on the travel time observations of the sound waves transmitted through the abdominal medium. In the present study, aiming to realize the method as a clinically available equipment, body surface scanner machinery was developed keeping good contact between a transducer and a human abdominal body surface. To-and-fro movement scanning equipment including the attachment of the elastic coupling gel hemisphere in front of the transducer surface was installed. The optimum pushing status was controlled by monitoring the variation of the received sound wave amplitude. They were in stable over the wide pushing distance region, regardless of the contact surface angle. It was shown that measured precision of the travel time were good enough to discriminate the difference of the sound speed between the fat and protein regions in the human abdominal region.

Acoustic waves generated by a TA (ThermoAcoustic) laser pair

Sound waves and acoustic energy generated by two identical TA (ThermoAcoustic) lasers were analyzed and studied. SPL (Sound Pressure Level) meters and microphones were employed to measure and study the sound waves at different distances from the openings of the TA laser pair for different laser position arrangements. The sound waves of the two TA lasers at or near the focusing point were found to be almost 180° out of phase when the distance between the openings of the two lasers was within about two tube diameters and the angle between the laser axes did not exceed 135°. As the distance increased, it became difficult to control the two TA lasers in synchronized operation. For separation distances greater than three times tube diameter, the sound wave amplitudes and the phase difference between the two laser outputs varied periodically with time. With the openings of the two TA lasers touching each other, the frequency of the sound waves increased when the angle between the laser axes was very close to 180°. In this case, the glass tube opening was no longer a pressure anti-node and the wavelength of the fundamental mode reduced to approximately twice the tube length.

열음향(Thermoacoustic) 레이저의 음향파 특성 분석

Sound waves and acoustic energy generated by two identical TA (ThermoAcoustic) lasers were analyzed and studied. One end of the ceramic stack was heated by a thin NiCr wire wound around that end. The other end of the stack was cooled by natural convection of atmospheric air. The wavelength of the sound waves generated by a single TA laser was four times the tube length and the amplitude of the waves increased with the heating rate. SPL (SoundPressure Level) meters and microphones were employed to measure and study the sound waves at different distances from the glass tube opening and at the focusing point of the TA laser pair for different laser position arrangements. The sound waves of the two TA lasers at the focusing point were found to be almost 180 degrees out of phase when the openings of the two lasers were very close to each other and the angle between the laser axes was small. When the two TA lasers were placed far apart, the sound wave amplitudes and the phase difference between the two laser outputs varied periodically with time. The frequencies of the sound waves changed when the openings of the two TA lasers were in close vicinity and the angle between the laser axes exceeded a certain value. In this case, the glass tube opening was no longer a pressure anti-node and the wavelength of the fundamental mode was not equal to four times the tube length.

Objective sound wave amplitude measurement generated by a tuning fork. An analysis of its use as a diagnostic tool in suspected femoral neck fractures

IntroductionHip injuries are becoming a more common problem as the elderly population increases and their management represents a significant proportion of health care costs. Diagnosis of a fracture based on clinical assessment and plain films is not always conclusive and further investigations for such occult fractures, such as magnetic resonance imaging (MRI), are sometimes required which are expensive and may be difficult to access. Disruption to the conduction of a sound wave travelling through a fractured bone is a concept that has been used to diagnose fractures. Patients and methodsIn our study we used a tuning fork with frequency of 128Hz to objectively measure the reduction in sound amplitude in fractured and non-fractured hips. We looked at the feasibility of using this test as a diagnostic tool for neck of femur fractures. ResultsA total of 20 patients was included in the study, using MRI scan as the standard for comparison of diagnostic findings. Informed consent was obtained from the patients. There was a significant difference in the amplitude reduction of the sound waves when comparing normal to fractured hips. This was 0.9 in normal hips, compared to 0.31 and 0.18 in intra-capsular and extra-capsular fractures, respectively. Our test was 80% accurate at diagnosing neck of femur fractures. ConclusionIn conclusion this test may be used as a diagnostic test or screening tool in the assessment of occult hip fractures.

Wind speed measurement by paper anemometer

A simple wind speed measurement device, a paper anemometer, is fabricated based on thetheory of standing waves. In providing the working profile of the paper anemometer, anexperimental device is established, which consists of an anemometer sensor, a sound sensor,a microphone, paper strips, a paper cup, and sonic acquisition software. It shows that thesound wave detected in the paper cup has a larger amplitude and the noise isdepressed, though the frequency of the sound is twice that detected directly fromthe strip. From the experiments, we find that the frequency of the sonic wavedoes not change with wind speed; however, its amplitude increases with windspeed. To predict the wind speed, a correlation is established from the sound waveamplitude.

Sound generation by spheroidal metallic nanoclusters embedded in transparent matrix under the action of laser pulses

The theory of the photo-acoustical effect caused by a laser action on metal nanoclusters embedded in a dielectric matrix is build. The energy absorbed by clusters propagates through the dielectric matrix and generates the sound waves in it via the thermodeformation mechanism. The formulae for an acoustical signal are derived, and the high sensitivity of the sound wave amplitude to the shape of metal clusters, as well to such parameters of a laser irradiation as the frequency, polarization, and intensity, is revealed. The behavior of the sound vibrations amplitude in a region of the surface plasmons absorption is studied in detail. It is found that this amplitude at light absorption by a discrete metal film (a system of clusters in the matrix) can exceed the corresponding amplitude for the absorption by a continuous metal film in the region of plasmon resonances by several orders of magnitude.

Acoustic energy output and coupling effect of a pair of thermoacoustic lasers

SUMMARY Two identical TA (ThermoAcoustic) lasers were constructed, tested, and characterized for the generation and manipulation of high-amplitude acoustic waves from heat. Pyrex glass tubes with one open end and ceramics used in automobile catalytic converters were employed to fabricate the TA lasers. The ceramic stack in each TA laser was heated by a thin NiCr (nichrome) resistance wire at one end, and cooled at the other end by radiation and natural convection of atmospheric air. Generated acoustic energy and sound waves were analyzed for different power input rates and laser position arrangements. Changes in wave amplitude and phase difference due to triggered excitation and cross talking between the two TA lasers were investigated. Also tested and characterized were the focusing and synchronization of the two laser outputs for manipulating the acoustic waves and energy intensity. Direct applications of large quantities of acoustic energy generated by multiple TA lasers were addressed. It was found that the sound waves generated by a pair of identical TA lasers were almost 180° out of phase when the openings of the two lasers were very close to each other, resulting in much lower sound energy levels at the focusing point. When the two lasers were placed far apart, the phase difference between the two laser outputs varied with time. Amplitudes of both sound waves increased slightly when the two laser outputs were in phase. Copyright © 2011 John Wiley & Sons, Ltd.

J054031 音波共鳴法による水の蒸発係数測定([J05403]マイクロ・ナノスケールの熱流体現象(3))

We propose a new method for measurement of the evaporation coefficient using sound resonance experiment based on a theory of molecular gas dynamics. The evaporation coefficient is one of the parameters contained in the kinetic boundary condition. The evaporation coefficient of water is determined from the pressure amplitude of resonant sound wave in a cylindrical space bounded by a sound source and a vapor-liquid interface. By comparing the pressure amplitude with a linear theory based on molecular gas dynamics, we prove that the evaporation coefficient of water is about 1.0 around 300K.

Changes in sound transmissibility through the canine thorax due to the experimental pleural effusion

The authors studied the effects of pleural effusion on sound transmissibility through the canine thorax. In the supine position, dogs received sound ranging from 100 to 1000 Hz at the tracheostoma. Using the microphones attached to the dorsal and ventral part of the chest wall, the relative level of the transmitted sound wave was determined in reference to the amplitude of the sound wave at a tracheostom. Measurements of sound transmissibility were performed before and after injecting saline into the bilateral pleural space which was intended to be experimental pleural effusion. In the dorsal part, the experimental pleural effusion decreased sound transmissibility in the frequency range between 100 and 300 Hz. At 100 Hz, the pleural effusion of 5, 10, and 15 ml/kg/hemithorax caused a decrease in sound transmissibility by 3.7 +/- 3.7, 6.6 +/- 4.9, and 10.0 +/- 5.7 dB, respectively. In the ventral part, the reduction in sound transmissibility in the low frequency range due to the pleural effusion was small. In contrast, introduction of pleural effusion caused an increase in sound transmissibility by 5 to 9 dB in the frequency range above 500 Hz. We consider that these changes in sound transmission are implicated in the physical findings such as "aegophony" and reduction in vocal fremitus or vocal ausculation.

Resonant mode conversion in superfluid 4 helium and in solids.

One component of the success of the Westervelt analysis of the parametric array was that sound propagation in most gases and liquids exhibit very little dispersion. Therefore, the pump waves and their nonlinearly generated product propagate at very nearly the same speed. When an acoustic medium can support more than one sound mode with different propagation speeds, then a parametric array can be created by the nonlinear interaction of the two slower sound waves to produce the faster wave, if the slow wave propagation directions are not collinear. Bulk superfluid helium, at temperatures below 2.1 K, will support a slower (thermal) sound mode and a faster (mechanical) sound mode. An experiment performed in 1977 will be described that used a waveguide to create thermal (temperature‐entropy) sound waves while controlling their angle of intersection. A mechanical (pressure‐density) wave was produced and its amplitude determined the thermodynamic coupling constant between density changes and the Galilean invariant square difference in the normal and superfluid particle velocities that characterize the thermal sound wave amplitude. An earlier experiment will also be described that demonstrated the nonlinear conversion of two shear waves to a longitudinal wave in aluminum. [Work supported by the Office of Naval Research.]

Numerical simulations of frequency shift and amplitude alteration of sound waves in random mass density and velocity fields

We investigate the effect of space-and time-dependent random mass density and velocity fields on frequencies and amplitudes of small sinusoidal acoustic waves. The dispersion relations and their approximate solutions, which are valid in the limit of weak random fields and long sound waves, are presented. These approximate solutions are verified by numerical simulations for the full set of hydrodynamic equations. The main findings are: (a) both the analytical and numerical results reveal that random fields affect the frequencies and amplitudes of sound waves. A space-dependent (time-dependent) random field leads to wave attenuation (amplification). Random mass density and time-dependent random velocity fields lift up frequencies of sound waves. A space-dependent random velocity field produces redshifts in frequencies; (b) in the limit of validity of analytical solutions the numerical results are close to the analytical data; (c) for a stronger random field and for shorter sound waves, numerical and analytical data depart from each other.

Physical properties and behavior of shock waves

The distinguishing feature of a shock wave is its practically instantaneous rise in pressure. Its laws of propagation are different from those for ordinary, continuous-waveform sound waves, even when the sound wave amplitude is finite. The Rankine–Hugoniot shock relations connect the properties on either side of the shock, e.g., pressure, density, and particle velocity, with the shock velocity or Mach number. These relations are valid even for unsteady shocks, e.g., growing or decaying shocks. Weak shock theory provides a means of predicting the propagation of most steady and unsteady shocks that are encountered in acoustics, including those used in medicine. For example, in lithotripsy the focal pressure amplitude rarely exceeds 100 MPa; for such a shock the shock velocity is only ∼8% greater than the sound speed in water. Shock rise time τrise is an interesting property of shocks but often difficult to measure. For example, if the lithotripsy shock cited above was steady and in water, its rise time would be a few tens of picoseconds. When the shock is unsteady, τrise is much harder to predict.

Nonlinear behavior of poroelastic absorbing materials

A theory for the non-linear acoustic behavior of porous materials with an elastic frame composed of incompressible grains or fibers has been derived. Johnson’s expression for complex flow resistivity [D. L. Johnson et al., J. Fluid. Mech. 176, 379–402 (1987)] has been combined with the dependence of dc flow resistivity on the amplitude of particle velocity (Forchheimer’s nonlinearity). The frame compressibility has been assumed to be linear. The system of coupled nonlinear equations for slow and fast planar compressional modes propagating in the material has been solved approximately by method of slow varying amplitudes. As a result of calculations the dependence of surface impedance on the amplitude of sound wave has been obtained for either fixed or moving surfaces. For all of the parameter values considered so far, it is predicted that the amplitude of the reflection coefficient increases with the incident sound intensity. This approach has been extended to allow for waves reflected from rigid backing of a layer of material. The influence of nonlinearity on the impedance of a sample of finite thickness has been estimated. [Work supported by USARSDG (UK), Contract No. R7D 8901-EN-01.]

Hénon-like attractor in air bubble formation

We studied the formation of air bubbles in a submerged nozzle in a water/glycerol solution inside a cylindrical tube, submitted to a sound wave perturbation. It was observed a route to chaos via period doubling as a function of the sound wave amplitude. We applied metrical as well as topological characterization to some chaotic attractors. We localized a flip saddle, and we also could establish relations to a Hénon-like dynamics with the construction of symbolic planes.

Sound attenuation system and related method

The present invention is noise attenuation system and related method for suppressing noise generated by a noise source, such as a jet engine, contained in a housing. An impedance device is positioned in the housing to attenuate the amplitude of sound waves generated by the noise source propagating in one direction and to create a reflected sound wave. The reflected sound wave is out of phase with the sound waves propagating from the noise source away from the impedance device. The reflected sound wave destructively interferes with this sound wave to attenuate the amplitude.

The Resonant Interaction of Sound Waves with a Large Amplitude Entropy Wave

We derive an asymptotic solution of the one-dimensional compressible Euler equations that describe the resonant interaction of small amplitude sound waves with a large amplitude entropy wave. The large entropy variations are assumed to occur only in small regions. We show that the sound wave amplitudes satisfy a two-by-two system of strictly hyperbolic partial differential equations with a quadratic flux.

Kinetic Effects on the Ion Sound Waves Generated by Stimulated Brillouin Scattering of a Spatially Smoothed Laser Beam

Stimulated Brillouin Scattering (SBS) can drive ion sound waves to amplitudes such that steepening and particle kinetic effects occur. Such phenomena have been studied recently in spatial volumes corresponding to a single laser speckle, in two (Cohen B I et al 1997 Phys. Plasmas 4 956), and three spatial dimensions (Vu H X 1997 Phys. Plasmas 4 1841). We analyze the results of 2D kinetic simulations modeling the evolution of SBS in the case of a spatially smoothed laser beam interacting with a plasma containing many speckles. For this purpose, we have coupled a 2D particle-in-cell code to a 2D non-paraxial electromagnetic wave solver. The generation of a fast ion population is observed to initially take place in the most intense hot spots, resulting in a decrease of the amplitude of the ion sound wave amplitude generated by SBS in these hot spots. SBS activity is consequently reduced in the most intense laser speckles, so that the overall backscattering SBS reflectivity drops considerably below the values expected from models that do not account for particle kinetics and/or nonlinear hydrodynamics.