[en] This is a brief survey of the role of physical acoustics in exploring the superconducting and more particularly the superfluid state. The nature of 1st, 2nd, 3rd, 4th, and 5th sound, and ways in which they are used to measure superfluid properties are described

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[en] The cited reports discuss superfluidity in liquid helium, with both helium 3 and helium 4 considered. Topics discussed include phase studies, heat transfer, hydrodynamics, rotons, zero sound, first sound, second sound, third sound, and fourth sound

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[en] The equations describing the propagation of the first, second and fourth sound in the relativistic theory of superfluidity are derived with account for dissipation. The expressions for the velocity of the first, second and fourth sound are obtained. (author). 4 refs

[en] The theory of sound propagation in superfluid helium is reviewed. The theory of first, second, fourth and third sound is considered. A simple approximate derivation of the velocity of third sound is given and the Doppler shift of first, second, third and fourth sound is discussed. Experimental aspects of first, second, third and fourth sound are considered in turn. For first sound consideration is given to first-sound transducers, cavitation in liquid helium and velocity at the lambda transition. Second-sound transducers and the velocity of second sound at the lambda transition are discussed. Experimental aspects of third-sound transducers, the velocity and attenuation of third sound, the critical velocity of superfluid films and the thickness of a moving film are then discussed. Various aspects of fourth sound are considered. (B.R.H.)

[en] In Part I of this series, a theory of helium II incorporating the effects of quantum healing and relaxation was developed. In this paper, the propagation of first, second, and fourth sound is discussed. Particular attention is paid to sound propagation in the vicinity of the lambda point where the effects of relaxation and quantum healing become important

[en] The microscopic theory of liquid helium II due to Fliessbach [T. Fliessbach, Nuovo Cimento D 13, 211 (1991)] allows a certain amount of entropy to be carried by the superfluid component. The experimental results tell us that the entropy carried by the superfluid component is smaller than 2% with respect to the total entropy. The nonstandard model of liquid helium II deduced from extended thermodynamics is not in contrast with the theory by Fliessbach. In this work, using this model, we show that accurate measurements of the speeds and the attenuations of the first, second, and fourth sounds in liquid helium II allow the determination of this small superfluid entropy, or, at least, they will establish an upper bound for this quantity

[en] In the spirit of the Landau theory of Fermi liquid, the paper considers the solution of an isotropic superfluid Fermi liquid in a superfluid Bose liquid. On the basis of the kinetic equation for the Fermi particle distribution function, a three-velocity hydrodynamics for such a solution has been derived in the limit of ωtau < < 1. There have been obtained sonic solutions of hydrodynamics equations; temperature dependences have been investigated of velocities of the first, second, third and two fourth sounds under all temperatures. In the high frequency limit ωtau > > 1 there have been obtained two sonic solutions of the kinetic equation, one of which with T > Tsub(c) turns into a zero sound in a solution of a normal Fermi liquid in a Bose liquid. All physical values have been expressed through Fermi liquid constants. There has been considered the problem of critical rates of a solution of a superfluid Fermi liquid in a superfluid Bose liquid