摘要:

The absorption of sound in emulsions and suspensions is due to viscous and thermal transport processes occurring at the interface of the nonhomogeneities, as well as to the intrinsic absorption in the materials comprising the system. A complete description of these processes for systems of fluid particles suspended in fluid media was given by Epstein and Carhart [J. Acoust. Soc. Amer.25, 553 (1953)]. However, subsequent investigators of liquid systems have generally neglected the thermal transport process. We show in this work that the Epstein‐Carhart results provide a good description of our experimental attenuation data in emulsions, and that the thermal transport process can be the major factor in the attenuation. We have here also extended the theory further to include the attenuation in suspensions of solid particles, and good agreement is found between our theory and experimental results for aqueous suspensions of polystyrene spheres.

ISSN:0001-4966    

DOI:10.1121/1.1912999

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

By assuming that air is composed of four gases (i.e., nitrogen, oxygen, water vapor, and carbon dioxide) and applying energy transfer rates for the binary collisions inherent in such a system, absorption of sound in the atmosphere has been predicted. The calculated curves based upon 24 energy transfer mechanisms are compared with experimental data over the humidity range of 0–100% relative humidity. Agreement between theory and experiment is very good. By including classical absorption and rotational relaxation effects, the total atmospheric absorption is also predicted at 20°C. Calculations made for various concentrations ofCO2indicate that lowCO2levels (less than 0.1%) do not significantly affect absorption of audible sound at high humidities. At very low humidities, however,CO2is an important factor.

ISSN:0001-4966    

DOI:10.1121/1.1913000

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

A number of solids sustain large elastic compressions under shock‐wave loading. In these solids, measurements of the stress and compression in the direction of shock propagation can be used to calculate both third‐ and fourth‐order longitudinal elastic constants if measurements are carried out over a wide range of compressions. Only limited measurements of fourth‐order constants have been previously determined by other techniques. Determinations of third‐order constants under these large elastic compressions afford the opportunity to test the applicability of the finite‐strain formulation of constitutive relations. A general method for calculating these third‐ and fourth‐order constants is presented and applied to shock compression data for sapphire and fused quartz. For sapphire, it is found thatC111 ≈ C333 = − (3.3±0.3) × 104 kbarandC1111 ≈ C3333 = + (5.0±1.5) × 105 kbar. For fused quartz, it is found thatC111 = + (5.5±0.1) × 103 kbarandC1111 = + (110±10) × 103 kbar. The technique and method of analysis seem generally applicable to solids that exhibit elastic limits of a few percent of their longitudinal elastic constants.

ISSN:0001-4966    

DOI:10.1121/1.1913001

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

In this paper we describe a novel method of probing a sound field in three dimensions with a focused light beam. In our method, the spatial‐temporal modulation impressed upon the light by the sound is extracted by the use of either polarization sensitive elements or spatial filters placed in front of a photodiode. The technique is inherently capable of high‐resolution sampling because, as is shown, phase and amplitude of the resulting rf current are indicative of the complex sound pressure in a narrow region around the focus of the light beam. This is in contrast to earlier methods using a narrow collimated light beam which only give an indication of sound‐pressure amplitude and phase integrated over the entire width of the sound field traversed by the light beam. The first part of the paper analyzes the mode of operation and discusses sensitivity and resolution in a heuristic manner. The second part provides experimental results for various frequencies and sound media. The third part treats the rigorous theory.

ISSN:0001-4966    

DOI:10.1121/1.1913002

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Acoustic velocities in platelike elastic materials satisfying certain conditions can be measured by irradiating the materials with ultrasound and processing the ultrasonic transmission patterns with laser light to obtain Bragg diffraction of the light. Simple observation or measurement of the diffracted optical image as the acoustic frequency is varied gives both compressional and shear‐wave velocities through the materials. A real‐time visualization of the acoustic transmission pattern can also be obtained. This method provides a simple means of detecting inhomogeneities in platelike material and obtaining a quantitative comparison of the velocity characteristics with reasonable precision in localized regions.

ISSN:0001-4966    

DOI:10.1121/1.1913003

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Values of the nonlinearity constant “D,” which are instrumental in conversion of the acoustic phonons to thermal phonons, are determined in this paper for copper in the temperature range from 300° to 80°K, using experimental data of third‐order elastic constants of this material. The previously predicted temperature‐dependent behavior of this constant D, which found experimental support partially at room and liquid‐nitrogen temperatures only in Ge, has been thus tested for the first time on experimental basis even for a metallic crystal. The results are found to be in agreement with the previous prediction. Moreover, the temperature‐dependent curve for phonon viscosity component of hypersonic attenuation can be recalculated by using our values of D. When this is done, a better agreement is obtained than that obtained previously between the theoretical and corresponding experimental curves of hypersonic attenuation as a function of temperature for longitudinal wave propagation in the (100) direction.

ISSN:0001-4966    

DOI:10.1121/1.1913004

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Sound velocity and absorption coefficient have been measured for three antiferromagnetic crystals—MnO, CoO, and NiO—at 23±1°C by the pulse superposition method and the pulse‐echo method, respectively. Elastic constants have been calculated from the velocity data:c11= 22.20,c12= 10.99,c44= 7.83 for MnO:c11= 25.56,c12= 14.36,c44= 8.03 for CoO; andc11= 27.0,c12= 12.5,c44= 10.5 for NiO (in 1011dyn/cm2). The absorption coefficients are found to be proportional to square of frequency between about 60 and 500 MHz for MnO and CoO and between 10 and 50 MHz for NiO. The absorption of the shear wave is of comparable order to that of the longitudinal wave in the paramagnetic phase (MnO and CoO), and this fact suggests that single‐ion magnetostrictive interaction rather than the volume magnetostrictive interaction is a dominant cause for the acoustic attenuation in these materials.

ISSN:0001-4966    

DOI:10.1121/1.1913005

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

A comparative analysis is given for zero‐mode transmission of torsional and longitudinal harmonic waves in an idealized drill string of uniform pipe sections with uniform coupling joints. Multiple passbands are shown to exist with successively increasing and then decreasing bandwidths. The longitudinal‐wave passbands have the wider maximum pass bandwidths but successively occur at higher frequencies where a non‐idealized system may have more attenuation.

ISSN:0001-4966    

DOI:10.1121/1.1913006

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

This paper extends the investigation of critical‐angle phenomena and investigates the relationships between material properties and the condition (F0) for which zero reflectivity occurs. It was found that material attenuation, density, and velocity all influenceF0. Graphs are presented for several materials from which the reader may determineF0for a particular sample. Measurements which further verify the accuracy of the model, which we have used in these calculations, are also presented.

ISSN:0001-4966    

DOI:10.1121/1.1913007

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

Extensive and highly accurate tables have been calculated for the radiation impedance functions of a rigid rectangular piston mounted in a rigid infinite baffle radiating into a half‐space. This was accomplished by developing a numerical technique of general applicability which yields a highly efficient computer algorithm. The latter computed 3792 highly oscillatory integrals containing branch point singularities, each to 7D accuracy, in a total of 74 sec on a CDC 6400 computer.

ISSN:0001-4966    

DOI:10.1121/1.1913008

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP