摘要:

Diffraction of two dimensional elastic waves by a cylindrical cavity in a half‐space is considered in this paper. The paper is divided into two parts. In the first part we use an integral representation for the scattered displacement field to derive its asymptotic behavior at large distances from the cavity. We also give a formal derivation of the representation of the displacement field in terms of multipolar potentials. In the second part we use a method of matched asymptotic expansions to calculate the scattered field. Numerical results are presented for the surface displacements due to Rayleigh waves scattered by a circular cylindrical cavity.

ISSN:0001-4966    

DOI:10.1121/1.382147

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A perturbation analysis is presented for calculating the inextensional natural frequencies of curved elastic arcs. Variation of the radius of curvature along the arc length is accounted for by considering the curvature to be a perturbation from a constant curvature, and utilizing the method of strained parameters. Frequencies thus derived for hinged parabolic arcs demonstrate good agreement with finite element solutions. The analysis could easily be extended to determine the natural frequencies of noncircular curved plates and shells.

ISSN:0001-4966    

DOI:10.1121/1.382148

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A parabolic wave theory is considered in which the energy flux through an elemental aperture is required to lie in directions measured relative to a ’’local’’ principal propagation direction that can be termed narrow angled. This can be compared to the more commonly encountered theory, in which a ’’global’’ principal propagation direction is used. A propagation model is then developed which is formulated in terms of an acoustic field measure termed the acoustic intensity angular spectral density. The relationship between this propagation model and the geometric theory is considered, with the latter being recovered in the appropriate limit. A sample calculation is carried out for the behavior of a beamed signal in the vicinity of a point caustic.

ISSN:0001-4966    

DOI:10.1121/1.382149

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

We develop simple approximations for the bulk acoustic parameters associated with coherent waves in pair‐correlated random distributions of scatterers small compared to wavelength, and indicate their relations to earlier forms. Our initial functional equation for the bulk index of refraction applies for dense gas and liquid‐state statistics in terms of integral analogs of lattice sums involving appropriate pair‐correlation functions. For small‐spaced scatterers (average separation of closest neighbors small compared to wavelength) we obtain explicit closed forms for the radiation loss effects by reducing the integrals to simple correlation‐packing functions based on the scaled‐particle equations of state for impenetrable particles. For uncorrelated sparse distributions, the present results reduce to those obtained by elementary procedures for small perturbations in the properties of the imbedding medium. For random lattice‐gas statistics (a model for uncorrelated distributions which takes into account the space‐occupying property of the obstacles), the results reduce, in general, to those obtained before for scatterers excited by the coherent wave and radiating into the imbedding medium.

ISSN:0001-4966    

DOI:10.1121/1.382150

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Polar polymer such as PVC, PVF and PVF2show strong piezoelectric activity after being stretched and poled. They were used up to now in plane or cylindrical configurations. We show that such polymers can be moulded and poled, which constitutes a new generation of piezoelectric transducers. Example is given of a high range loudspeaker using a moulded PVC film.

ISSN:0001-4966    

DOI:10.1121/1.382151

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

It is here argued that the commonly held view of organ pipe oscillation as pipe‐controlled ’’edgetone’’ oscillation is misleading. Edge‐related effects, being of higher multipole order than the pipe‐related air motion, are inherently less efficient, and may be ignored in the presence of strong resonator coupling. It is proposed that the term edgetone or ’’jet‐edge oscillation’’ be applied to a free jet‐edge (or weakly coupled pipe) situation, while a normal resonant organ pipe oscillation should be referred to as ’’pipetone.’’

ISSN:0001-4966    

DOI:10.1121/1.382152

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Stiffnesszof the basilar membrane of the house mouse against a displacement by sound was calculated from data on width and thickness of the membrane. Three functions of the kind log10z=ax+bwere obtained which equally express the stiffness change in dependence on the locusxon the basilar membrane. These functions were compared with the one for frequency representation. The result is that the spatial distribution of displacement maxima for frequencies and of stiffness follows the same kind of place‐dependent functions over a large portion of the basilar membrane. From this it can be concluded empirically that the frequency and stiffness (calculated from width and thickness of the basilar membrane) scales along the cochlea are generally proportional to each other and that stiffness is a dominant factor for the determination of the locus of the displacement maximum for a given frequency.

ISSN:0001-4966    

DOI:10.1121/1.382153

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.2033228

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.2033229

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.2033232

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP