Vol 70, No 2 (2024)

A method is proposed for reconstructing the acoustic parameters of a medium by iterative processing of the coherence matrices of the acoustic field of random sources, for some of which their power density is known. The possibilities of increasing the stability and accelerating the convergence of the method are discussed. The reconstruction results are compared with the functional-analytical approach based on the processing of the scattering amplitude.

This work shows the results of experimental study of the impact of 3D printing with 100% filling on the elastic properties of samples made of ABS filament. The dependence of the deformation and the relative change in the velocity of elastic waves on the applied mechanical stress (up to rupture) for the initial and 3D-printed samples of ABS polymer were measured simultaneously by both the static method and the Thurston-Bragger method. As a result of the experiment, linear and non-linear Young’s moduli and the 2nd order non-linear acoustic parameter were calculated. It was established that the selected 3D printing mode almost does not change the strength characteristics of the ABS polymer, and the plastic characteristics are slightly improved. A difference was found in the behavior of nonlinear parameters for the original and 3D-printed samples under mechanical loading, which is associated with changes in the internal structure of the samples caused by 3D printing. For the 3D printed sample, a decrease in the nonlinear parameter was found as the load increased.

The interaction of a pressure pulse with a gas-liquid zone, which is a section of a flooded multiphase jet consisting of a mixture of water and oil and containing a bubble core of methane, is numerically investigated. The possibility of determining the degree of expansion of the jet, the volume content of oil and gas in the jet from reflected signals is shown.

The acousto-optical characteristics of a paratellurite crystal with a cut angle α = 10.2° have been studied theoretically and experimentally. The crystal is used in an acousto-optical filter for processing optical images in visible and infrared light. The electrical tuning range of the filter was experimentally determined based on the frequency dependence of the power absorbed by the piezoelectric filter transducer. Estimates of the filter tuning range based on optical wavelengths have been made. At light wavelengths λ = 1.15 and λ = 0.63 μm, the dependences of the Bragg angle of incidence on the ultrasound frequency were calculated. When measuring the diffraction efficiency in the deflector operating mode, it was found that the tuning range of the filter over optical wavelengths turns out to be different from that predicted by measuring the electrical characteristics of the converter and becomes narrower.

An experimental verification of the possibility of estimating the coordinates of a mobile marine robot using small-sized vector-scalar antennas spaced apart in space, a broadband emitter placed on board the robot, and a remote polyharmonic permanently installed emitter – a “beacon”, which is used to eliminate bearing shifts caused by rotation receiving antennas under the action of underwater currents. It is shown that the use of technical means installed in the waveguide makes it possible to solve the triangulation problem and determine the horizontal coordinates of the robot, while taking into account the ray structure provides an estimate of the depth.

On the example of an underwater sound channel typical for the Philippine Sea [1–3], it was established by numerical simulation using the mode theory that during experimental studies of the propagation of explosive signals by R.A. Vadov [1–3] the manifestation of the weakly divergent beam in the space-time structure of the acoustic field was observed for the first time. The effect consisted in the registration at certain locations of the corresponding points in the oceanic waveguide, along with the classical quadruples of pulses, of additional acoustic signals with small time delays relative to them.

An analysis of the basic properties of the scalar frequency-wave spectrum of turbulent pressures, representing the total energy of the wave components of the turbulent pressure field with a given wave vector modulus, has been carried out. Consideration of the scalar spectrum, which has independent applied significance, allows us to visualize the energy distribution of turbulent pressures in a wide range of frequencies and wave numbers. Based on well-known vector wave field models, relations are proposed for estimating the reduced scalar spectrum. The degree and nature of the parametric influence of the Mach and Reynolds numbers are determined.

The paper presents the results of comprehensive studies of the phenomenon of slow relaxation of the speed of sound in structurally inhomogeneous materials after vibration exposure to a finite amplitude of deformations. The results were obtained on the experimental setup created for these studies, which ensured high accuracy in measuring the linear and nonlinear acoustic characteristics of various materials. The results of an experimental study of relaxation in a carbonate rock, which is a structurally heterogeneous material with a complex system of internal bonds, are presented. The measurements made it possible to determine the dependences of the relaxation parameters on the amplitude and excitation time, as well as the effects due to the finite amplitude of the probing wave. An interpretation of the obtained results is given and the effects that have not received an exhaustive explanation are noted.

The possibility of evaluating the quality of thermodiffusion welding of two yttrium aluminum garnet crystals in a composite optical disk has been investigated using an optoacoustic method. To obtain acoustic images of thermodiffusion welding. an optoacoustic sensor connected to a pulsed laser (wavelength 532 nm. pulse duration 10 ns) by an optical fiber was scanned over the disk surface. The ultrasonic pulses in the frequency range up to 80 MHz were registered synchronously with the movement of the transducer on the area of 16x16 mm with a step of 0.1 mm. Two modes of ultrasonic location were used: on reflection and on lumen. Diagnostics of two 15 mm diameter composite disks with different quality of thermodiffusion welding was carried out. The possibility of quantifying the quality of the diffusion layer by an optoacoustic method for objective comparison of the disks is discussed. The obtained data are confirmed by the results of measurements by the optical projection method.

The issue of auditory perception of speech and piano sounds, which have a relatively weak fundamental tone level against the background of high harmonics (formants of the vocal cords and string overtones, respectively), is considered. It is shown that the audible spectrum of these sounds is the spectrum of the interference envelope of oscillations of the corresponding harmonics. This spectrum contains the fundamental tone as the dominant sound, which is clearly heard in speech and music, while the formants and overtones, initially dominant in the sound spectrum of speech and music, primarily affect the timbre of the fundamental tone. At the hypothesis level, it is indicated that the vibration interference envelope is isolated (detected) as a result of the propagation of sound waves in the nonlinear fluid medium of the cochlea of the inner ear.

Information services for acoustics, which are provided by the portal “Acoustics. Russian-language sources”, consists of three parts – magazine, signal and search. An important part of the portal, the magazine part, is the full-text archive of the “Akusticheskiy zhurnal” for all the years of its existence, starting from 1955. The archive has been posted in the public domain on the website http://www.akzh.ru for more than 10 years. The current state of the Archive is given in many respects: structure, statistics on content, authors, users and much more.