Kazakov L.I. «On A Sound-Absorbing Coating in the form of a Layer of a Viscous Liquid with Bubbles» Acoustical Physics, 70, № 1, с. 39-50 (2024)

The study considers the possibility of creating a broadband sound-absorbing coating for hydroacoustic measuring tanks and chambers with inertial or soundproof walls, consisting of a layer of viscous liquid with gas bubbles. The coatings are calculated using the well-known theory of sound propagation in a liquid medium with bubbles, as well as the Kramers–Kronig integral dispersion equations. It is shown that the volumetric size distribution function of bubbles should be constant over the entire range of their sizes. A viscous liquid is designed to increase bubble damping to a value on the order of unity that is optimal for coatings by adding viscous losses in the surrounding liquid to small thermal losses. Low-frequency compensating resonators are used in coatings for soundproof walls. Several examples of calculating the acoustic characteristics of coatings are given.

Nartov F.A., Williams R.P., Khokhlova V.A. «Electronic Focus Steering Capabilities of a Diagnostic-Type Linear Ultrasound Array Designed for High Power Therapy and Its Visualization» Acoustical Physics, 70, № 1, с. 165-174 (2024)

The focus steering capabilities of a 1 MHz linear phased array transducer (64 rectangular elements, 14.8×51.2 mm aperture) intended for drug delivery applications in abdominal organs were assessed and compared with its design-stage computer model. Acoustic fields generated by the transducer and predicted by the models of an ideal array with uniformly vibrating elements and either a plane or a cylindrically focused surface were simulated using the Rayleigh integral and angular spectrum methods. The boundary conditions for the transducer were reconstructed from acoustic holography measurements performed for selected focusing configurations of the array and also synthesized from holography data measured for each of its individual elements. It was shown that the transducer field with electronic focus steering can be accurately synthesized based on the holography data of its elements, which significantly simplified acoustic field characterization. Variability of the power and directivity patterns of the array elements were analyzed. A twofold smaller range of electronic steering in the transverse direction for the transducer compared to its computer model is discussed.

Tsysar S.A., Rosnitskiy P.B., Asfandiyarov S.A., Petrosyan S.A., Khokhlova V.A., Sapozhnikov O.A. «Phase Correction of the Channels of a Fully Populated Randomized Multielement Therapeutic Array Using the Acoustic Holography Method» Acoustical Physics, 70, № 1, с. 82-89 (2024)

The acoustic holography method was used to characterize a therapeutic focused fully populated 256-element ultrasonic transducer array. Elements of the array with the shape of equal area polygons are densely arranged in an irregular pattern on a spherically concave surface with a radius of curvature of 150 mm and a diameter of 200 mm. The array has a central frequency of 1.2 MHz and is designed to operate in water. The performance of individual array elements was studied based on the holographically reconstructed normal velocity distribution over the array surface. It was shown that with the same electrical signals applied to the elements, their acoustic responses had a phase deviation relative to the nominal values, which can be caused either by the asphericity of the array surface, or by the introduction of additional phase delays by the electrical matching network. To compensate for the detected parasitic phase shifts of the elements and restore the effective sphericity of the radiating surface, the Verasonics V-1 control system was used. The hologram measured after making the correction, as well as the shape of the focal region and acoustic pressure magnitude at the focus, separately measured by a hydrophone, showed that the proposed method reconstructed the nominal operating parameters of the array with high accuracy.

Kurashkin K.V., Kirillov A.G., Gonchar A.V. «Use of Longitudinal Critically Refracted Waves to Determine Residual and Temperature Stresses in Rails» Acoustical Physics, 70, № 1, с. 51-57 (2024)

The possibility of using longitudinal critically refracted waves for acoustic strain gauging of longitudinal residual and temperature stresses in rails is studied. The influence of stress and temperature on the propagation velocity of elastic waves in rail steel is analyzed theoretically. An algorithm is presented for determining longitudinal stress in a rail by measuring the propagation time of longitudinal critically refracted waves. The operational principle is described, and the main parameters of an acoustic strain gauge device are presented, in which a differential scheme for measuring the propagation time of longitudinal critically refracted waves is implemented. Longitudinal critically refracted waves that propagate along a rail are emitted and received from the rolling surface of a rail head using contact piezoelectric transducers fixed on the polymethylmethacrylate wedges. The results of acoustomechanical and temperature tests are presented. The measurement errors are calculated. The results of determining the level of residual welding stresses in the head of a new rail are presented. The experimental results are compared with theoretical estimates of the stresses that arise in a rail under the influence of temperature, as well as with available data in the literature on residual stresses in rails.

Kozlov V. «On the first bifurcation of Stokes waves» Алгебра и анализ, 36, № 2, с. 70-92 (2024)

Stokes water waves on the vorticity flow in a two-dimensional channel of finite depth are treated. In author’s paper published in JDE, 2024, the existence of subharmonic bifurcations on a branch of Stokes waves was proved. Such bifurcations occur near the first bifurcation in the set of Stokes waves. Moreover, it was shown in that paper that the bifurcating solutions build a connected continuum containing large amplitude waves. This fact was proved under a certain assumption concerning the second eigenvalue of the Fréchet derivative. In this paper this assumption is investigated and explicit conditions ensuring it are presented. Ключевые слова: solitary waive, nonlinear water wave theory, flow of infinite depth, crest, amplitude.

Kurashkin K.V., Kirillov A.G., Gonchar A.V. «Use of Longitudinal Critically Refracted Waves to Determine Residual and Temperature Stresses in Rails» Acoustical Physics, 70, № 1, с. 51-57 (2024)

The possibility of using longitudinal critically refracted waves for acoustic strain gauging of longitudinal residual and temperature stresses in rails is studied. The influence of stress and temperature on the propagation velocity of elastic waves in rail steel is analyzed theoretically. An algorithm is presented for determining longitudinal stress in a rail by measuring the propagation time of longitudinal critically refracted waves. The operational principle is described, and the main parameters of an acoustic strain gauge device are presented, in which a differential scheme for measuring the propagation time of longitudinal critically refracted waves is implemented. Longitudinal critically refracted waves that propagate along a rail are emitted and received from the rolling surface of a rail head using contact piezoelectric transducers fixed on the polymethylmethacrylate wedges. The results of acoustomechanical and temperature tests are presented. The measurement errors are calculated. The results of determining the level of residual welding stresses in the head of a new rail are presented. The experimental results are compared with theoretical estimates of the stresses that arise in a rail under the influence of temperature, as well as with available data in the literature on residual stresses in rails.

Kurazhova V. «Adult Speech in Different Emotional States: Temporal and Spectral Features» Acoustical Physics, 70, № 1, с. 175-181 (2024)

The aim of the study is to determine individual features of adult speech in different emotional states. The acoustic speech characteristics of 12 adult native Russian speakers were studied. The speech of informants uttering meaningless phrase in different emotional states was audio recorded: joy, anger, sadness, fear, and neutral. The temporal and spectral characteristics of speech were analyzed in the Cool Edit Pro sound editor. The maximum pitch range in male speech is revealed in phrases uttered in a neutral state and a state of joy; the minimum, in a state of sadness. For female speech, the maximum pitch range is in a state of joy and in a state of anger; the minimum, in a state of sadness and in a neutral state. The pitch range in female speech is larger than that in male speech. For seven informants, it was shown that the duration of utterances in a state of sadness was longer compared to other states, and in a state of joy, on the contrary, it was minimal. Both male and female utterances in a state of joy were characterized by maximum pitch range values; conversely, in a state of sadness, by minmum values. Pauses between words in utterances in a state of sadness were detected in both men and women. Thus, differences in the temporal and spectral characteristics of utterances in different emotional states are revealed. The individual features of the manifestation of the emotional state in the speech of adults are determined.

Mansfeld D., Belyaev R.V., Volkov G.P., Kuzmin A.A., Sanin A.G., Shaikin A.A. «Monitoring the Internal Temperature of Active Elements of High-Power Lasers Using Ultrasonic Probing» Acoustical Physics, 70, № 1, с. 68-75 (2024)

Monitoring the internal temperature of active elements (AE) of high-power lasers is necessary for their safe operation. The article describes a method and device for monitoring the internal temperature of the AE of lasers. The measurements utilize pulsed ultrasonic (US) probing and the temperature dependence of the sound speed in the AE material. A change in the sound speed leads to a change in the phase of the ultrasonic signal passing through the object, which is recorded by the described device. The results of monitoring the AE temperature using ultrasonic probing during operation of a laser device are presented.

Aksenov S.P., Kuznetsov G.N. «Interference Invariants in Hydroacoustic Field Maxima in Deep Water» Acoustical Physics, 70, № 1, с. 105-115 (2024)

Chuprov’s interference invariant (II) well describes the properties of a sound field in shallow water. However, the question of how applicable Chuprov’s II concept is to deep water, where the patterns of sound field decay with distance are more complex has been insufficiently studied. Therefore, the authors studied the II properties in the near and far fields of acoustic illumination, as well as in the shadow zone. A new definition of the invariant was proposed and studied, and its characteristics were compared with Chuprov’s II as a function of distance, reception and emission depths, and summer or winter propagation conditions. The new invariant is called the phase-energy invariant (PEI), since orthogonal components of the phase gradient are used to describe the spatial sound energy distribution. The stability of the new invariant, its independence on different influencing factors, and its natural change with distance from zero to one are shown. It has been established that in winter conditions, at almost all distances, the PEI is equal to unity, and the II does not have stable values and varies jumpwise over a very wide range. In summer conditions, in the shadow zone, with increasing distance, the PEI increases, just like the II, from close to zero to one. In the near and far fields of acoustic illumination, the PEI is approximately equal to unity, and the II in these zones, both in summer and winter, is characterized by unlimited oscillations, caused by division by a value close to zero. It is shown that the definition of PEI is valid both in single-mode waveguides and in free unbounded space with a dispersive medium.