Amplitude Sound Waves Research Articles

Chaotic behavior in bubble formation dynamics

We constructed an experimental apparatus to study the dynamics of the formation of air bubbles in a submerged nozzle in a water/glycerin solution inside a cylindrical tube. The delay time between successive bubbles was measured with a laser-photodiode system. It was observed bifurcations, chaotic behavior, and sudden changes in a periodic regime as a function of the decreasing air pressure in a reservoir. We also observed dynamical effects by applying a sound wave tuned to the fundamental frequency of the air column above the solution. As a function of the sound wave amplitude, we obtained a limit cycle, a flip bifurcation, chaotic behavior, and the synchronization of the bubbling with sound wave frequency. We related some of the different dynamical behaviors to coalescent effects and bubble sizes.

Analytical scalings for flame interaction with sound waves

Analytical scalings for the problem of flame interaction with acoustic waves of controlled intensity are obtained on the basis of the linear equation for a perturbed flame front. Both stabilization of the hydrodynamic flame instability by sound waves of small amplitudes and excitation of the parametric instability at the flame front by sound waves of sufficiently large amplitudes are considered. The stability limits obtained analytically agree well with the previous numerical calculations. Besides, the analytical results for the minimum amplitude of sound waves needed to induce the parametric instability and for the typical wavelength of the instability are in excellent agreement with the experimental results on propane flames.

Structure of a weakly ionized gas-discharge plasma

Analysis of the properties of weakly ionized plasmas suggests that strong collective interactions exist in them in spite of the large distance between particles. Arguments supporting this view are presented. First among these is the existence of “hidden” mass, which is observed in experimental measurements of the aerodynamic drag forces. The hidden mass causes an increase in the amplitude of sound waves in a plasma in comparison with an un-ionized gas at identical values of the gas parameters. Analysis of the experimental results shows that gas-discharge plasmas contain previously unknown structural formations that are specific to a plasma and are of a standard type for each species of gas, independent of the pressure and temperature of the plasma. The concentration of particles making up the structure in the plasma of a gas discharge in air is 0.22×1017 cm−3.

Determination of the elastic constants of some composites by using ultrasonic velocity measurements

An ultrasonic immersion technique was used to determine the velocity and amplitude of sound waves in composite materials. The materials under study were E-glass/IPN, E-glass/PET, Kevlar 29/IPN, Dyneema/PE and Dyneema/Kraton. The velocity and amplitude of longitudinal and transverse sound waves at the frequency of 1 MHz were measured in three planes of symmetry at several angles of incidence. The complex stiffness matrix for the composites was calculated.

Neutron backscattering on vibrating silicon crystals-experimental results on the neutron backscattering spectrometer IN10

Neutron backscattering on vibrating silicon crystals has been measured in transmission geometry on the backscattering spectrometer IN10 at the Institute Laue-Langevin (ILL). The crystals were excited into longitudinal mechanical resonance vibrations by LiNbO3 transducers glued to the crystal surface. The transmitted intensity of the 111 Bragg reflection was measured as a function of the deformation amplitude at vibration frequencies from 2.5 MHz to 30 MHz. By vibrating the initially perfect silicon crystal, an increase in ΔE/E of the diffracted profile was achieved, accompanied by an increase of the backreflected intensity. The width of the reflection and the resolution is a linear function of the ultrasonic strain over a wide range of excitation strengths. ΔE/E can be easily tuned in a reproducible way by varying the voltage on the piezoelectric transducer. For the highest excited ultrasonic strain an increase of the backscattered intensity of about a factor of 50 is observed. Sound wave amplitudes can be determined from the measured width in ΔE/E of the transmission curves. The obtained results are relevant for the design and operation of intensity-to-resolution tunable monochromators for high resolution instruments.

Head movement during listening turns in conversation

In five subjects, head movement during conversation was monitored by polarised light goniometry, and recorded alongside speech and a signal proportional to peak amplitude of sound waves (‘peak loudness’). Kinematic properties of listeners' head movements, such as amplitude, frequency and cyclicity, differentiated various conversational functions. That is, they were function-specific: symmetrical, cyclic movements were employed to signal ‘yes’, ‘no’ or equivalents; linear, wide movements anticipated claims for speaking; narrow linear movements occurred in phase with stressed syllables in the other's speech (‘ynchrony’ movements); and wide, linear movements occurred during pauses in the other's speech. That, it is argued, bears upon the relation between thesignalling of communicative intentions and the synchronisation of interactional rhythm. Thus, the former appears to determine the timing and tempo of responses such as ‘yes’ and ‘no’, while the latter determines the regulation of ‘synchrony’ movements. The manner in which these factors interact in other conversational functions and their theoretical implications are discussed.

Time dependence and saturation of Brillouin backscatter

A model is developed in which saturation of Brillouin scattering occurs through the mechanism of damping of the ion sound wave. The damping is taken to depend on the ratio of ion to electron temperature and on the ion sound wave amplitude, so as to include the effects of both Landau damping and particle trapping, while the effect of sound wave damping on the ion temperature is taken into account in a self-consistent way.

Frequency dependent dissipation onset in 4He films

Abstract Limiting effects in the amplitude of third sound waves emanating from a critical flow region near the source have been used to determine the onset of dissipation in thin 4 He films at various frequencies. It is found that at higher frequencies the film is less stable at a given flow velocity.

Quasi-stationary nonlinear waves in nuclear matter close to pion condensation

The nuclear hydrodynamic model is extended to include the fluctuating spin-isospin density and its interaction with the nuclear matter density. Using the TDHF equations, it is shown that the dynamics of these densities interacting with the pion field can be expressed in terms of the generalized pressures derivable from the generalized nuclear matter equation of state. A phenomenological Skyrme interaction model is used to obtain these pressures. A theory of pion-like spin-isospin quasi-stationary nonlinear waves is formulated from the generalized hydroequations describing the dynamics of a coupled pion nuclear matter system. In the lowest order of nonlinearity, it is proved that the amplitude of the spin-isospin sound wave satisfies a nonlinear Schrodinger equation. The solution of these equations is the amplitude modulated pion-like solitary waves in nuclear matter. When this matter is near the pion condensate, the speed of these nonlinear waves is much smaller than that of the ordinary sound waves.

On the scattering of sound by internal waves in the ocean

The parabolic approximation to the wave equation is applied to the calculation of the spectral density of amplitude and phase fluctuations of a plane sound wave propagating through a random field of internal waves in the ocean. The dependence of the predicted spectra on wave number and frequency shows that the lowest-mode internal waves dominate the phase variance, while the amplitude fluctuations are controlled by intermediate scales. The results are compared with previous theories and available data. There is a discrepancy between observed amplitude spectra and predictions based on the internal wave models. It is concluded that internal waves are not solely responsible for the scattering of sound in the ocean and that other effects must contribute.

On the scattering of sound by internal waves in the ocean

The parabolic approximation to the wave equation is applied to the calculation of the spectral density of amplitude and phase fluctuations of a plane sound wave propagating through a random field of internal waves in the ocean. The dependence of the predicted spectra on wave number and frequency shows that the lowest mode internal waves dominate the phase variance, while the amplitude fluctuations are controlled by intermediate scales. The results are compared with previous theories and available data. There is a discrepancy between observed amplitude spectra and predictions based on the internal wave models. It is concluded that internal waves are not solely responsible for the scattering of sound in the ocean and that other effects must contribute.

Some applications of atmospheric acoustics

Acoustic methods for atmospheric research have become powerful and increasingly useful tools. The physical properties available from—and limitations of—remote sensing of the atmosphere by echosondes (acoustic sounders) are briefly discussed. Such instruments exploit the amplitude and phase fluctuations of sound waves produced by random processes in the atmosphere to the measurement of the statistical properties of the physical mechanisms involved. A particular application describes how acoustic measurements of the turbulence-strength parameters CT and Cv, and the horizontal wind gradient Uz by a combined monostatic-bistatic Doppler echosonde provides the critical parameters u*, T*, and L* required in surface-layer similarity theory. The important advantages on extension of such acoustic measurements to the entire boundary layer are explored.

Coherent Scattering of Sound Waves by Isotopic Impurities in a Crystal Lattice

An infinite crystal containing a single plane of isotopic impurities is considered, and by using the Green's function technique, the amplitudes of sound waves scattered by the plane are calculated in the first Born approximation. The scattered waves are shown to be plane waves reflected and transmitted at well-defined angles. Similarities and differences with the corresponding electromagnetic case are noted and discussed.

セメント・モルタル・ブロックを用いた音波の減衰の測定

A measurement to obtain attenuation characteristics of sound wave amplitude and velocity through cement mortar or across artificial gaps was carried out.Followings were concluded:1. Sound wave velocities measured in this measurementwere about 4, 700m/s and the velocity obtained on a wet condition was slightly higher than the value obtained on a dry condition.2. Sound velocity changes across gaps was evedently found on a dry condition, but not on a wet condition. However, it was found even on a wet condition, when the sound passed through 5 or more gaps.3. Much energy disperses at a gap, especially on a dry gap.4. Changes of wave shape were recognized after travelling across a gap or more gaps.

Interferometric Method for Measuring Ultrasonic Light Diffraction Spectra

An interferometric method for measuring light diffraction spectra of phase gratings produced by ultrasonic sound waves travelling in media is described. The diffracted light beam is heterodyned by the reference light beam coming from the same He-Ne gas laser as for the diffracted beam. Since the frequency of the diffracted beam is shifted according to that of the ultrasonic waves and the spectral order, the spectra are obtained by measuring the beats between two beams. Clear spectra were obtained for the waves travelling in water and the method will have various applications, such as exact measurements of the velocities and the pressure amplitudes of sound waves in media.

Oscillatory Behavior of Ultrasonic Attenuation in Superconducting Nb-Zr Alloys

The attenuntion of ultrasonlc compressional waves at frequencies of 5 to 30 Mc is studied in superconducting Nb and Nb --Zr alloys. Large fluctuations are observed in the attenuation as the temperature is varied from 1 to 4.5 deg K. It is concluded that these fluctuations are characteristic of the superconducting state, since application of the critical magnetic field destroys the structure observed; that the fluctuations are probably related to pressure and/or charge- density modulations; that the attenuntion is strongly frequency-dependent; and that the attenuation is independent of the sound-wave amplitude at small strains in the frequency range studied. The mechanism underlying the attenuation fluctuations is studied, in terms of the filamentary theory of hard superconductors. (T.F.H.)

Effect of Nonlinear Losses on the Design of Absorbers for Combustion Instabilities

Investigations were conducted to provide a basis for the design of multiple-resonator absorbers to control high amplitude combustion instabilities (screech) in high output combustors. An impedance tube technique was employed to determine the effect of high amplitude sound pressure waves ou the absorption characteristics of absorber configurations having open areas varying between 0.5 and 10 per cent. Frequencies were varied between 200 and 1200 cps. It was found tha t the acoustical impedance of the absorbers contains a nonlinear facing resistance which depends on the oscillating velocity and particle displacement in the absorber neck, and tha t the nonlinear resistance can generally be correlated with the amplitude of the incident pressure wave plotted on a decibel scale. A design procedure is presented in which the absorption characteristics of perforated liners for a particular sound wave amplitude can be calculated from known physical dimensions.

Method of Measuring Sound Velocity Amplitude in Tubes over the Audio and near Ultrasonic Range

A method of measuring the velocity amplitude of sound waves propagated in hollow tubes is described. A conducting quartz fiber is stretched across a cross section of the tube where the latter is pervaded by the magnetic field of a permanent magnet. The potential difference across the oscillating fiber is recorded on an oscilloscope. Velocity amplitudes have been measured for frequencies up to about 20 000 cps. An approximate relation is derived for the velocity amplitude as a function of the generated potential. It has been found that the method is much freer from disturbances over the above frequency range than a similar method in which the cooling effect by the sound wave on a current heated wire or fiber is used. Some observations made during the production of quartz fibers sputtered with gold are reported.

Propagation of Sound Waves in the Atmosphere

The effect of humidity on the velocity of sound waves is investigated (Eq. (5), Table I). The radius of curvature for a ray of sound which is propagated in the direction of the wind is given [Eq. (13)] and discussed. The amplitudes of sound waves as a function of the distance are given [Eq. (17)], and the relative importance of the quantities involved is discussed.

Societies and Academies

LONDON Physical Society, May 11.—E. G. Richardson: The amplitude of sound waves in resonators. After a consideration of the relations between the ‘pipe’ and the ‘Helmholtz resonator,’ graphs of the variation of amplitude, obtained by means of a hot-wire anemometer traversed through various types of resonator, are reproduced. By means of a calibrated manometer of the vibrating membrane type, some direct values of the impedance of orifices are obtained. Traverses across an orifice through which the air is vibrating in simple harmonic form are obtained with the hot wire: these show a tendency for the air to vibrate with greater amplitude in annuli remote from the centre of the orifice.—R. E. Clay: The focus of a gas-filled X-ray tube. Pinhole photographs of the focus obtained with various radii of curvature of the cathode and various distances from the anticathode are discussed; it is concluded that with the tubes of the type considered, a radius of about 2 cm. and a distance of 3 or 4 cm. are the best conditions.