摘要:

It is shown theoretically that plane longitudinal sound waves traveling in an electrically conducting plate will generate complex electric currents provided there is a magnetic induction perpendicular to the particle displacement. The currents react with the induction to produce a complex mechanical force which opposes the particle motion. The impedance associated with this force effectively modifies the impedance of the medium by adding a resistance and a stiffness reactance. The induced resistance attenuates the waves while the induced stiffness increases Young's modulus and therefore increases the sound velocity.Of all the elements, it appears that this effect is a maximum in lithium, i.e., at a given frequency and induction.

ISSN:0001-4966    

DOI:10.1121/1.1907150

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

A new apparatus for investigation of sound propagation constants for large amplitude audio‐frequency vibrations in metals is described. One novel feature of the apparatus is the use of tuned resonant supports that are tilted with respect to the specimen. The tilting minimizes the tendency to chatter due to the Poisson effect. Because the supports are driven at their resonant frequency, large amplitudes may be achieved without the occurrence of an energy loss due to slipping at the contact surfaces between supports and test specimen. The error caused by energy dissipation due to the internal friction of the support is, in most cases, negligible. In those cases where it is not negligible, it can be closely estimated and corrected for. Auxiliary equipment permits determination of the resonant frequency of the specimen to better than 1/1000. The total error in the determination of the logarithmic decrement varies between 2 percent and 5 percent.

ISSN:0001-4966    

DOI:10.1121/1.1907151

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The frequencies of tones when metal rings are struck in radial and axial directions have been investigated in a variety of steel and bell‐metal rings.The classical formulas relating frequency with ring dimensions and physical properties of the materials compare closely with actual measurements except for thick rings. The fundamental tone is predominant in the smaller rings but the fundamental fades and the overtones predominate as the rings increase in diameter and decrease in width and thickness.Comments are given on musical properties of rings which may be promising but which have not been fully explored.

ISSN:0001-4966    

DOI:10.1121/1.1907152

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The theory of the transmittivity of immersed plates is extended to include the effects of losses associated with shear waves. The loss is computed for the transmission maxima which occur for five modes of vibration and is compared with observations made at a fixed frequency of112 megacycles. The general agreement is is good but not within the experimental error for all of the five modes. The value of the loss factor, which was determined to give agreement in a simple case, is difficult to appraise without data at other frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1907153

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

A nondimensional number(Δp/ρ)12/ftforprimary Pfeifentönerelating the dependence of differential pressure Δpacross orifice to density of gas ρ, thicknesstof orifice‐plate terminating pipe, and frequencyfofprimary Pfeifentöneis obtained by dimensional analysis. Correlation of experimental data presented on the basis of this number indicates that it is relatively constant in numerical value over range of variation of the parameters, pipe length, orifice diameter, differential pressure across orifice, andPfeifentonfrequency, studied.

ISSN:0001-4966    

DOI:10.1121/1.1907154

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Some numerical values have been computed for the functions which arise in connection with the scalar wave equation in rotational paraboloidal coordinates. Tables of these values are given with the aid of which a numerical analysis is carried out of the scattering of a plane sound wave by a rigid convex paraboloid of revolution. The surface of the paraboloid is defined bykξ0=0.25 and the direction of propagation of the plane wave makes an angle of 36.9° with the axis of symmetry of the paraboloid. The asymptotic expansions of the scattered waves are discussed and their amplitudes are tabulated. The magnitude and phase angle of the total pressure are evaluated at points on the surface of the paraboloid.

ISSN:0001-4966    

DOI:10.1121/1.1907155

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

For low acoustic frequencies, a mixture (a porous medium or a suspension) is shown to have an effective density which differs slightly from the density given by Archimedes' principle. This effective density is computed from a physically elementary consideration of viscous, incompressible fluid flow. For higher frequencies, pore or particle size in the mixture becomes comparable with the wavelength of shear waves in the fluid, while still small compared with dilatational wavelength. The theory is extended to such frequencies through the known formula for the fluid's resistance to the oscillations of a rigid sphere. In both cases, the effective compressibility of the mixture is taken to be the volume‐average of the component compressibilities. From the effective density and compressibility, the acoustic properties of the mixture are predicted. Predictions are compared with previous theories and with experimental results.

ISSN:0001-4966    

DOI:10.1121/1.1907156

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Abnormal propagation of sound in the east‐to‐west and west‐to‐east directions has been studied throughout a period of a year. Experiments were carried out over the California‐Arizona desert using explosions of 1200 pounds of TNT. Returns of sound from altitudes of 30 to 50 km were consistently received to the east in winter and to the west in summer. Sounds which traveled to the high temperature region at 80 to 100 km altitude were received about one‐fifth of the time. Sounds were returned from the second region somewhat better to the east ha summer and to the west in winter. An early arriving abnormal wave was received at ranges greater than 400 km.

ISSN:0001-4966    

DOI:10.1121/1.1907157

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

An extensive survey is made of the chemical effects of ultrasonic waves. Increased understanding of the mechanism of these effects is sought through a consideration of the significance of certain experimental variables such as frequency, intensity, pressure, and temperature. Also considered is the role of cavitation.

ISSN:0001-4966    

DOI:10.1121/1.1907158

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The ultrasonic absorption coefficients in water solutions of magnesium sulfate were measured at 30 Mc as a function of temperature and concentration. Temperatures from 0 to 30°C and concentrations from 0.05 to 2.00 molarity were used. Measured data were used to calculateQ, the absorption cross section per molecule of magnesium sulfate at several temperatures.Qis defined by (2αM/ν2)/NwhereNis the number of molecules of magnesium sulfate per cc, ν is the frequency, and αMis the amplitude absorption coefficient caused by the magnesium sulfate. These are constant for concentrations up to 1‐molarity but decrease by 50 percent for 2‐molarity concentration. The constant values ofQ×1037, 25 at 25°C, 30 at 20°C and 37 at 15°C indicate an activation energy for the magnesium sulfate absorption process at 30 Mc of 6.8 kcal/mole°K.

ISSN:0001-4966    

DOI:10.1121/1.1907159

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP