Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

Ultrasonic investigation of cholesteric liquid crystals

Abstract: This paper reports experimental results for the velocity and absorption of ultrasonic waves in the mesomorphic states of four cholesteric liquid crystals, namely, cholesteryl nonanoate, decanoate, oleate, and linoleate. The absorption has been measured by a pulse technique and velocity by an acoustic interferometer, both at a single frequency of 2 MHz. The results obtained for these materials furnish distinct similarities with the behavior of pure normal materials in the critical region. Anomalous increase in absorption and decrease in velocity observed across the isotropic–mesomorphic transition temperature in each case are interpreted in terms of pretransitional effect.

Method for pumping liquids e.g. for acoustic waves propagation, requires use of thin substrate for propagating acoustic surface waves

Abstract: A method for pumping liquids involves bringing the liquid (L) being pumped into contact with a surface (11,21) of a substrate (1,2) and exciting acoustic sound waves on this surface, and using mode-conversion, generating sound waves in the pumped liquid. To excite and transmit the acoustic surface waves, a substrate (1,2) is used having such a small thickness (d) that on its inner surface (11,21) facing the pumped liquid and on its outer surface (12,22) facing away from the liquid, mutually correlated acoustic surface-waves are propagated. An independent claim is included for a device for pumping liquids.

Dynamic localization of acoustic waves in superlattices.

Abstract: The absorption and change in velocity of acoustic wave interacting with electrons in a superlattice irradiated by an infrared laser field are investigated. Near the roots of the equation s 0 /4d=|J 0 (eFd/Ω)| (24 and d are the miniband width and period of the superlattice, F and Ω are amplitude and frequency of the laser field, and so is the sound velocity) a strong renormalization of sound velocity and intense absorption peaks are predicted. These phenomena have a straightforward relation with the dynamic localization of electrons and are called dynamic localization of acoustic waves

The Propagation of Sound in Carbon Dioxide Near the Critical Point

Abstract: The expression for the normal velocity of sound in a fluid becomes indeterminate at the critical point since the coefficient of elasticity tends to zero and the specific heat at constant pressure approaches infinity. An expression has been obtained for the isentropic slope which does not become indeterminate at the critical point. Observations were made with a Pierce type variable path acoustic interferometer placed completely inside a pressure tank with provisions for external control. The isothermal variation of velocity and absorption was measured as a function of pressure at 572 kc in carbon dioxide. Above the critical temperature it was found that, as the pressure increases, the velocity decreases steadily, goes through a sharp minimum, and rises abruptly. Below the critical temperature a discontinuity in velocity was observed between liquid and vapor. The velocity in the liquid at 29°C was 208 meters/second, and in the vapor 179 meters/second. The velocity variations away from the critical point agree with previously published results. The attenuation decreases steadily with increasing pressure and shows an abrupt rise as the critical point is reached, which would be expected from critical fluctuation scattering. Using isotherm data two values of the velocity at the critical point were calculated, 154 and 146 meters/second. The measured value was found to be 141.6 meters/second.

Experiments on the Propagation of Plane Sound Waves in Tubes I: The Adiabatic Region: II: The Transition Region

Abstract: I. An experimental investigation using an acoustic interferometer with a magnetostriction source is described. Results on attenuation and velocity in tubes of radius 0.013 cm and upwards, from 10 to 20 kc/s, and for a variety of tube materials and gases are given. These confirm modified Kirchhoff's formulae. II. The velocity and attenuation of plane sound waves in tubes of radius 0.02 cm have been measured in the transition region between adiabatic and isothermal flow.