Том 71, № 1 (2025)

A brief review of the studies of the acoustic signal of a parametric antenna in the ocean at megameter distances is given. The features of the propagation of a broadband signal of a parametric antenna in a shallow-water marine waveguide are also discussed. In this case, the frequency dispersion of the sound velocity in the marine waveguide allows for the compression of a broadband single-mode signal. Such compression leads to an increase in the efficiency of marine environment sounding. The possibility of branching propagation of directional acoustic radiation in an inhomogeneous ocean is discussed. It is shown that nonlinear acoustics opens up new possibilities, not implemented by known methods, for the use of hydroacoustic antennas in long-range signal propagation in a heterogeneous marine environment.

A theoretical study of nonlinear acoustic effects arising from harmonic excitation of a rod resonator with dislocation hysteresis of Granato-Lucke and linear dissipation has been carried out using the perturbation method. Expressions for the resonance curve, nonlinear losses, and shift of the resonant frequencies and the amplitude of the third harmonic are obtained. A graphical and numerical analysis of the obtained results is carried out.

The universal theory of “parametric” sound emitters is presented, taking into account the attenuation and diffraction of interacting waves in the quasi-optical approximation. Expressions are given that describe the structure of the low-frequency field excited by high-frequency waves with arbitrary amplitude and phase distributions on the surface of pump converters. Universal formulas for calculating directional patterns are given. The dynamics of pattern formation is described. The results of calculating the regime of highly distorted pump waves containing shock fronts are presented.

In this paper, the absorption and scattering of sound in suspensions with rotational movements of particles is analyzed. Such rotational (angular) oscillations are possible if the center of mass of the particle is shifted relative to the center of buoyancy. In such suspensions, there is a specific attenuation and scattering of sound. These effects can be used in the tasks of diagnosing suspensions in natural environments and in technological processes, as well as in the creation of metamaterials.

The use of technical means and methods of low-frequency hydroacoustics for monitoring the variability of average temperatures of underwater sound channels in the Sea of Japan is considered. A review of the characteristics of the line of powerful inter-piston hydroacoustic emitters developed by the Institute of Applied Physics of the Russian Academy of Sciences, developed by the Institute of Applied Physics of the Russian Academy of Sciences, is carried out, promising for organizing long acoustic routes. The results of measurements of the electroacoustic characteristics of low-frequency hydroacoustic emitters under natural conditions at depths of up to 150 m are presented, and the use of these emitters for studying the temperature regimes of associated underwater sound channels of the shelf and deep sea on multi-scale long routes in the Sea of Japan is also considered. Based on the processing of experimental data on an acoustic path with a length of about 1000 km, obtained in 2022, examples of the reconstruction of average water temperature values from data on the speed of sound along the acoustic path are given, the sensitivity of the method is assessed, and the signal-to-noise ratio values achieved in the experiment are analyzed.

A method for estimating the coefficient of sound reflection from the bottom of a waveguide based on field measurements using a vertical array at various distances from the source is discussed. To analyze the spatial-angular structure of the recorded field, the method of coherent states, borrowed from quantum theory, is used. The acoustic analogue of the coherent state expansion allows one to construct a filter to isolate the field component representing the contribution of a given narrow beam of rays. The ratio of the amplitudes of such a field component before and after reflection from the ground gives an estimate of the reflection coefficient of the central ray. The effectiveness of the approach was tested using numerical simulation data. The results of its application for processing data from a lake experiment are presented.

In this paper we study characteristics of reverberation interference that occurs in the marine environment when long tonal pulses are emmited and scattered signals are recorded using a so-called bistatic scheme, i.e. when the receiver is located at a large distance away from the transducer. Probing of water area with tone pulses is carried out thus the necessary resolution to study both the Doppler spectrum and the temporal development of the reverberation signal is achieved by selecting the proper pulse length. The presented theoretical model is applicable to both direct problem and reverse problems, which are forecasting the characteristics of reverberation for a given sea state, and determining the properties of the marine environment, mainly its near-surface layer, basing on the results of acoustic sounding. The model is based on the representation of a scattered signal in the form of a superposition of reflections from scatterers, which are distributed along the depth and moving along circular trajectories. Their speeds are determined by the maximum amplitude and period of wind waves. The article continues a series of studies and generalizes the previous results to the conditions of significantly separated in space sound sources and receivers. The modeling results are confirmed by experimental data, involving such parameters as the width of the Doppler spectrum and the law of decay of reverberation intensity over time.

The possibility of the use of the Rayleigh wave dispersion for the localization of the source of seismo-acoustic emission is investigated. Compensation for the dispersion distortion is at the heart of the well-known methods of wavefront reversal or time reversal methods. The peculiarity of the paper presented is the use of the dispersion dependence, which ismeasured during seismoacoustic signal recording, with subsequent processing of the data obtained. An example of such processing is presented for the data recorded in the field experiment. The results indicate on the prospectivity of developing the proposed method of data interpretation for seismoacoustic remote diagnostics of natural environments, e.g. for the search and localization of different types of inclusions.

The paper proposes a method for constructing an active cancellation system based on an algorithm with a block adaptation procedure in the frequency domain. The proposed method has a high convergence rate and can be implemented on a general-purpose computer. The results of the simulation modeling and experimental study of the effectiveness of the proposed active cancellation system on the created setup are presented. It is shown that using the method described in the paper for constructing an active noise control system, a suppression level up to 20 dB can be achieved on the experimental setup and up to 28 dB in the simulation model. Special attention is paid to the architecture of the experimental setup and the software used.

Acoustic methods of non-reactive medical laboratory diagnostics based on precision measurements of sound velocity and attenuation in biological fluids are discussed. These parameters are determined at different frequencies and at different fluid temperatures using high-quality resonators. The developed methods are implemented in the measuring acoustic analyzer “BIOM”. The device contains two ultra-small ultrasonic resonators (about 100 µl) in volume. The microprocessor system of the device controls two ultrathermostats and maintains temperatures in the resonators in the range (20–38)° C with an accuracy of ± 0.005° C. The developed special software makes it possible to determine the acoustic characteristics (speed and absorption of ultrasound) in blood serum, whole blood and plasma with a relative error of ± 5×10⁻⁴ in terms of ultrasound velocity and ± 10⁻² in terms of ultrasound absorption. This made it possible to determine the total protein, protein fractions, parameters of the lipid spectrum and apolipoproteins A₁ and B, as well as the elastic properties of patients' erythrocytes in vitro.