Pleiades Publishing Ltd

Abstract—Articulatory event detectors, i.e., detectors of transitions from one articulatory state to another, are formed on based on analysis of spectral–temporal inhomogeneities in a speech signal. A triad such as /pause–fricative–vowel/ is segmented and recognized in the space of the principal components of the response spectrum of the detector of the pause–fricative transition, the spectrum of the fricative at its peak energy, and the response spectrum of the detector of the fricative–vowel transition at this detector’s peak. The root-mean-square error with respect to manual marking for the onset of fricatives is, on average, about 12 ms, and for the moment of the fricative–vowel transition, about 5 ms. Triad recognition errors with the same fricative and different subsequent vowels, as well as triad recognition errors differing only in the presence or absence of vocal excitement, constituted a few percent.

Diffraction of a plane sound wave by the open end of an impedance-wall waveguide connected to an opening in an impedance screen is considered. The plane wave is incident on the waveguide from a free half-space. Two versions of the problem are considered: for a semi-infinite waveguide and for a finite-length waveguide with a specified bottom impedance; the impedances of the walls, screen, and waveguide bottom can be different. The finite-length waveguide can be treated as an open cavity in the impedance screen. For the cavity of zero length, the problem is reduced to the diffraction by an impedance insert in the impedance screen. The solution in the external region determines the scattered field; the solution in the internal region allows one to determine the directional pattern of an array of receivers located in the cavity. The problem is solved using the integral Helmholtz equation with a specially selected Green’s function that provides the fulfillment of the boundary conditions. Formally, the problem is reduced to an infinite system of algebraic equations. The computational results obtained for bistatic and monostatic scattering patterns are presented.

The square and triangular lattices are considered, where the uniform crack growth is accompanied by the wave radiation. The radiation energy and structure are studied. The energy radiated to the bulk of the lattice is found in a direct way. The radiation structure is described based on the crack problem solution and by means of the analysis of two-dimensional dispersion relations for the intact lattice. The mode III problem for square lattice is discussed in detail, whereas, in the case of the plane problem for the triangular lattice, the only those results are derived which follow from the two-dimensional dispersion relations. It is shown that there exists a finite crack-speed-dependent region of wavenumbers corresponding to the waves radiated to the bulk of the lattice. In the case of the triangular-cell lattice, in addition, one or several lattice Rayleigh waves are radiated. For the square lattice a complete solution for the wave field is presented with the crack-speed-dependent far-field asymptote. The latter is characterized by the wave amplitude asymptotically decreasing as the distance from the crack front in power −1/3. The asymptotically significant crack-speed-dependent direction of the radiation is determined. Such asymptotic results are also valid for the triangular lattice.

A method is developed for passive acoustic diagnostics of a mobile sound source in an oceanic waveguide, based on information on the frequency shifts of the maxima of the wave field and mode eigen-functions. An algorithm is formulated for solving the inverse problem. A numerical experiment demonstrates the possibilities of this method for reconstructing the trajectory, velocity, and depth of a source.

Several variational problems of sound absorption and scattering are solved using an impedance-based approach. Analytical expressions are derived for the surface impedances of the best absorber and a perfectly transparent body. A discrete surface structure (coating) is proposed for implementing their acoustic properties. Results of computer simulation are presented.

In terms of the effective medium method, conditions for the existence of leaky shear surface acoustic waves in a semibounded fine-layered magnetic superlattice consisting of ferrimagnetic and superconducting layers are determined. On this basis, the possibility of a resonance interaction between a surface elastic SH wave propagating in the magnetic superlattice and a shear bulk wave propagating in the adjacent nonmagnetic medium is investigated.

The paper studies the dependence of the potential noise immunity of a detection system and noise immunity of a detection system with an interference compensator on the array parameters, angular signal position and local noise, the degree of correlation of distributed noise and spectral densities of the signal power, noise, and interference. The gain in noise immunity of the detection system when the optimal spatial filter is used with respect to the use of an interference compensator is estimated as a function of the degree of correlation of distributed noise and the power of random amplitude–phase errors of the weight coefficients of the array.