Boqiang Z., Qiangqiang Z., Qingwen H., Tianpai F., Gao X., Xin J. «Bandgap Mechanism of Phonon Crystals Coupled to Acoustic Black Holes» Акустический журнал, 70, № 3, с. pp453-464 (2024)

In this study, phonon crystal structures embedded in acoustic black holes are discussed. The low-frequency band gap is widened by exploiting the low-frequency, broadband and multimode properties of the acoustic black hole. The energy band properties of the acoustic crystal structure embedded in an acoustic black hole are calculated by means of a finite element method. The mechanism of band gap generation is investigated. The vibration transfer characteristics of finite period structures are analyzed. The influence of the structural parameters of the acoustic black hole is analyzed. The results show that the acoustic crystal structure embedded in an acoustic black hole has multiple band gaps in the 500 Hz band and the band gap coverage is increased to 45.18%. The starting bandgap is 16.10% lower than before embedding in the acoustic black hole and the width of the first bandgap expands to 173.03% of that before embedding in the acoustic black hole. The onset and termination frequencies of the first band gap are mainly determined by the vibrational modes of the scatterer and the acoustic black hole structure. The vibrational transfer of the finite period structure is analyzed and shows good damping characteristics in the bandgap interval. Finally, vibration experiments verify the vibration damping effect of the proposed coupled acoustic black hole phononic crystal, and the relevant findings of this paper can be used in the vibration damping design of plate structures, enriching the experience of research related to acoustic black holes.

Wang Z.Y., Yan Y., Gao Z., Shi B. «Inclined Crack Quantification of Plate-Like Structures Based on Circular Sensor Array and Lamb Waves» Акустический журнал, 70, № 3, с. pp560-569 (2024)

Cracks are one of the most common damages to thin plates. Therefore, rapid and accurate detection of cracks is of great significance in the nondestructive testing of thin plates. Most existing nondestructive testing technologies focus on crack localization rather than the quantification of the crack length and orientation. Therefore, this paper proposes a damage index, considering the wave attenuation during propagation, to quantify the crack length and orientation. Lamb waves are transmitted and received by a circular sensor array. Based on the abnormal reflection of the A0 mode of Lamb waves, the reflections at cracks are extracted by the Hilbert transform. The influence of the crack length and orientation are studied parametrically, and the relations between the proposed damage index and crack length and angle are given based on regression analysis.

Badykov R.R., Yurtaev A.A., Grigorev E.M., Lomachev A.O. «Manufacturing process simulation of a bump foil for a gas foil bearing» Динамика и виброакустика (Journal of Dynamics and Vibroacoustics с 2014 по 2016 № 2), 9, № 3, с. 6-15 (2023)

The paper describes the tools design process for manufacturing the bump foil of a radial gas foil bearing. The paper proposes an alternative technology for manufacturing the bump foil and a solution to the issues related to this technology, accounting for the compensating effects of residual elastic deformations after the manufacturing process. The significance of the finite element method implementation for residual deformations and stresses accounting is emphasized, aiming to minimize the negative impact of residual elastic deformation on the bearing operational parameters.

Gu X., Du J. «A Vortex Sound Model for the Prediction of Near-Field Aeroacoustic Noise from a Generic Side Mirror» Акустический журнал, 70, № 3, с. pp538-548 (2024)

A numerical model for investigating the aerodynamic sound generated by the interaction between flow and bluff body is developed, and then applied to the computation of near-field noise induced by the turbulent airflow passing through a generic side mirror. The flow field is simulated by employing the viscous vortex method. Then the sound sources within the computational domain are extracted from the simulated results with a vortex sound equation. The sound waves, sum of radiated sound and scattered sound, are determined using a time-domain boundary element method combined with the convolution quadrature method for improving the stability of the time marching algorithm. Further, the fast multipole method is adopted to enhance the computational efficiency. The computed pressure coefficients and surface pressure fluctuations match the measurements and simulations very well, and the obtained spectra of near-field aerodynamic sound are also close to the measured results. The comparisons of computed results of two additional cases with the previous studies demonstrate convincingly that the proposed model can effectively predict the flow-induced near-field noise.

Yadav Saurabh, Gupta Arpan «Lateral Movement of Particles in a Levitating Acoustic Field» Акустический журнал, 70, № 4, с. pp635-640 (2024)

Acoustic levitation is an interesting technique used for levitating small objects/materials using sound waves. In this study, lateral movement of levitating particles is demonstrated experimentally and numerically. The method can simultaneously move multiple particles and the paper demonstrates levitation for three particles. Initially, an ultrasonic tweezer with a resonance frequency of 40 kHz is used to levitate three particles of average weight of 0.15 mg each. The experimental design is based on numerical simulation. Further, the levitated particles are moved in a lateral direction using two ultrasonic tweezers setup by manipulating the phase of one of the tweezers using Arduino Nano. As evident by simulations, the movement takes place due to the interference of waves leading to the movement of pressure node. The lateral movement of particles can be controlled and even reversed by changing the phase difference.

Montano W.A., Gushiken E.I. «One year of sound monitoring since July 2020 during COVID-19 pandemic at one neighborhood in Lima, Peru» Noise Theory and Practice (Электронный ресурс), 7, № 4, с. 7-18 (2021)

В Лиме отсутствуют данные об уровнях звука до COVID-19, поскольку в городе отсутствует государственная сеть мониторинга звука. С июля 2020 года в одном из районов города проводится частный мониторинг шума. Были зарегистрированы изменения в звуковом ландшафте, которые были вызваны последовательными карантинами и блокировками из-за COVID-19. В анализируемом жилом районе один из источников шума исходит от движения автомобилей и автобусов; другой – от ночных полетов самолетов. Появление новых вариантов вируса вынудило власти ввести различные постановления о социальном ограничении, запрещающие мобильность людей; поэтому стало возможным измерить максимально низкий уровень шума, когда-либо существовавший. В этой статье анализируется уровень шума окружающей среды с июля 2020 года в одном районе Лимы, Перу в разные периоды COVID-19.