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Two absorption lines formed in the lower photosphere were used to study simultaneous velocity and intensity fluctuations. No significant correspondence was found between the locations of granules and those of oscillation, even when a time lag was included. This result supports the explanation of the origin of the oscillations as a self-excited sound wave rather than the local response to a granule excitation.

A brief kinematic analysis demonstrates one cause of sum and difference tones to be the interaction of sound waves with rotating blade rows. The sum tones are shown, paradoxically, to be always closer to cut-off than the incident wave, whereas the difference tones can be at a higher cut-off ratio.

The equation of state of a superdense degenerate Fermi gas is investigated within an extended 7-dimensional phase space. The equation of states obtained and the sound velocity are analyzed, and the equilibrium configuration curve is given for superdense astronomic objects, taking into account the equation of state mentioned and threshold creation of baryons and their resonances within the given formalism.

The magnetooptical, electrooptical and photoelastic behaviour of an elastic polarizable and magnetizable isotropic continuum are investigated from a dynamical point of view, starting from balance equations and constitutive relations. The most original result of the theory is the fact that the continuum exhibits the Cotton-Mouton effect, together with linear birefringence of transverse sound waves. This is compared with experimental data and quantum theory results. As expected, the continuum does not exhibit Faraday rotation.

The velocities of ultrasonic longitudinal waves have been investigated near the phase-transition point in single-crystalline Ca2Pb(C2H5CO2)6. The sound waves are coupled with electric polarizations by electrostrictive interaction. The anomalous part of velocity seems to display a logarithmic divergence near the phase-transition temperature Tc. Es werden die Geschwindigkeiten longitudinaler Ultraschallwellen in der Nahe des Phasenubergangspunktes in Ca2Pb(C2H5CO2)6-Einkristallen untersucht. Die Schallwellen sind mit elektrischen Polarisationen durch elektrostriktive Wechselwirkung gekoppelt. Der anomale Teil der Geschwindigkeit scheint eine logarithmische Divergenz in der Nahe der Phasenubergangstemperatur Tc widerzugeben.

It is shown that a mechanism exists which gives rise to narrow lines of paramagnetic resonance absorption of longitudinal sound waves, transverse sound waves and temperature waves in a liquid in spite of the rotational diffusion. The observation conditions for these resonances are discussed. The interaction of the molecular orientation with the fluctuations of shear stresses has been found to affect significantly the spin-lattice relaxation rate in a liquid.

When ultrasound is absorbed by tissue, heat is produced which may be destructive or, if controlled, can be therapeutic. In addition, ultrasound produces biological effects which cannot be explained on the basis of heating alone. Under certain exposure conditions production of ultrasonic lesions in brain tissue can be explained on a purely thermal basis. Examples of nonthermal effects of ultrasound include changes in growth, mitotic index and the production of chromosomal aberrations in plant roots.

Utilizing horizontal transmission paths located at various depths in the ocean, the attenuation of sound waves has been measured at nominal frequencies of 30, 45, 60, 75, 90, and 145 kHz. Analysis of the data indicates that both the relaxation frequency at 50 kHz, which is usually attributed to the presence of MgSO4 in the sea, and the associated compressibility are functions of pressure. As pressure increases, the relaxation frequency shifts upward with a corresponding downward shift in the chemical compressibility. Results are also given for the pressure coefficient of attenuation which permit more precise predictions of acoustic attenuation at frequencies within the range of this experiment.

The frequency down-shift in piezoelectric semiconductors due to spontaneous parametric amplification of sound waves has already been studied in different materials by Brillouin effect inside the high field domains, in particular in the growth of acoustic flux intensity. In this contribution, experimental results are given which prove the existence of an acoustoelectric current frequency change in photoconducting CdS apart from the presence of highfield domains crossing the sample. This change is equally due to a parametric exchange mechanism but is accompanied by a reduction of the acoustoelectric current which characterises this phenomenon. This behaviour in the amplification shall be studied following the crystallographic axis and at the same time in that off-axis. Le deplacement en frequence dans les semiconducteurs piezoelectriques dǔ a l'amplification parametrique spontanee des ondes sonores a deja ete etudie dans differents corps par effet Brillouin a l'interieur de domaines de hauts champs, en particulier au cours de leur croissance. Dans cet expose. nous presentons des resultats experimentaux qui prouvent l'existence dans le CdS photoconducteur d'un changement de frequence du courant acoustoelectrique en dehors de la presence de domaines de haut champ traversant l'echantillon. Ce changement est egalement dǔ a un mecanisme d'amplification parametrique et il est accompagne d'une reduction du courant acoustoelectrique qui caracterise ce phenomene. Nous etudions ce comportement a la fois pour l'amplification suivant l'axe cristallographique et hors de l'axe.

The elastic constants of a disordered Fe 72 Pt 28 single crystal have been measured as a function of temperature. All elastic constants behave highly anomalously below T c due to the Invar properties of this alloy. The magnetic contribution to the shear modes C '=( C 11 - C 12 )/2 and C = C 44 can be described by the relations - C ' m = K 1 ( M / M 0 ) 2 and - C m = K 2 ( M / M 0 ) 2 where K 1 and K 2 are magnetoelastic coupling coefficients. Using these relations the elastic constants at 0K are C '=0.3×10 10 N / m 2 and C =7.5×10 10 N / m 2 giving rise to an elastic anisotropy of A = C / C '=25. The elastic constant C L behaves differently. C L goes through a minimum at 50°C and a magnetically induced reduction is present up to 200° above T c . This is ascribed to a coupling between the longitudinal sound wave and spin fluctuations.

A waveguide partially packed with superleak and filled with superfluid 4 He is proposed as a useful configuration for studying acoustic modes. A calculation is performed indicating that the low-frequency propagating modes in such a system are of two types: a combined first/fourth sound mode and a modified second sound type mode. Experimentally, the waveguide is closed back on itself to form a toroidal resonator. Resonant frequencies were measured, and the experimental results compared favorably with the calculations. However, there remain unresolved discrepancies. This resonator may prove useful in measuring the possible superfluid properties of the new state of 3 He.

Analytic time solutions for the scattering of impulsive waves (the time-space Green function) by a rigid circular cylinder in an annular domain are obtained through a finite integral transform of the spatial variable.

This paper presents the results of calculations of the scattering of a plane sound wave from a prolate spheroid. Scattering patterns are given for the major axis equal to λ/π, 2λ/π, 3λ/π, for the ratio of axes equal to 0.10, 0.20, 0.29, 0.37, and for the angle of incidence measured from the major axis equal to 0°, 30°, 60°, 90°.

The problem of sound propagation near the critical point of a liquid-vapour system is considered. It is shown that a sound wave will develop into a shock wave in a time that becomes smaller close to the critical point. The shape, propagation velocity and the formation time of the shock waves are calculated.

Les resultats anterieurement obtenus pour des plaques elastiques isolees ou couplees sont etendus a des systemes heterogenes constitues par un support elastique et un revetement poreux, tel que du feutre. La transparence acoustique de ces systemes se trouve, moyennant des hypotheses tres generales sur l'absorption du son dans la couche poreuse, comprise entre deux bornes dont la valeur theorique est confrontee aux resultats de l'experience.

Geography is no longer taught as a two-dimensional subject, that is, the mere boundaries of certain surface areas. Our school geographies fifty years ago began to describe customs and manners and later chief industries, exports, etc., and so brought in the human factor. We may define geography today as "all that pertains to human environment." Are we wrong in suggesting that seismology for instance comes strictly within the purview of the instructor in geography? Is it not important that the class studying social and economic problems of the dwellers in our central southwestern states, should know quite a lot about the oil fields of Texas and Oklahoma. But these are now located mainly by using seismographs and we delve below the surface, although not very far, in interpreting the complex records of the transmitted earth waves due to explosive shocks. And the geographer should not stop with these skin-of-theearth phenomena. My colleague, Professor Reginald A. Daly, in his delightful paper "X-Raying the Earth," shows how geology is being remade today and that the geophysicist holds the center of the stage. It is not so much the features of the surface of the earth that we seek to study, as the layers below, even down to the core. Long elastic waves "set going when the hammer of the deadly earthquake strikes" caught on seismographs at widely separated observatories, bring to light the long hidden secrets of earth's concentric shells. Or again, the sonic depth finder or fathometer, by the echo of sound waves gives the lay-out of ocean bottoms. Surely the Professor of Geography must nolt omit the mention of these. It is then, we agree, entirely appropriate for the geographers to explore downward as well as superficially;' but if he can go down

The transmission of normally incident sound waves through a series of similar, equally spaced partitions has been calculated for the cases of infinite partitions and of circular partitions. The transmission characteristics depend on the solution of simultaneous linear difference equations for the velocity potentials. The array of partitions possesses interesting properties as a filter, and to illustrate these the change in intensity levels due to glass partitions is calculated numerically for 1, 2, 5, and 10 partitions.

We exhibit a dynamical model of particles in a two-dimensional lattice. We study a particular class of equilibrium states, and we investigate the simplest time correlation functions for these states. As a consequence, the propagation of sound waves with velocity $\frac{1}{\sqrt{2}}$ can be proved rigorously. A transport coefficient analogous to a viscosity is given by a Kubo-type integral formula. The convergence of the integral is discussed. Some preliminary computer results are reported.