Acoustical Physics最新文献

This study examines the performance of six different two-dimensional, 18-element microphone array geometries—BK, Ring, Reuleaux, Logarithmic, Triangle, and Starfish—for sound source localization. The arrays’ performances are systematically evaluated using beamforming algorithms and acoustic pressure reconstruction, focusing on key metrics such as main lobe width, side lobe magnitude, reconstruction error, and resolution quality over frequencies ranging from 0 to 3000 Hz. Additionally, the study investigates the adaptability of these configurations at various distances and explores their frequency-dependent behavior. The results indicate that array geometry substantially impacts localization accuracy, with the Starfish configuration demonstrating superior overall performance, exhibiting the narrowest main lobe width, highest main lobe amplitude, lowest reconstruction error, and consistently high resolution. Thus, the Starfish configuration is recommended as optimal for effective sound source localization applications.

Abstract—Damping (dissipation, energy losses) is the most important parameter of all mechanical oscillatory systems, in addition to elasticity and inertia. Its special role is due to the fact that it directly determines the maximum amplitudes of free and forced vibrations of systems and, accordingly, their dynamic strength and reliability, noise and ecology. Due to the poor study of the physical processes of damping, it is measured experimentally. This article presents one of the new efficient methods for experimental determination of losses, characterized by simplicity, high accuracy and a wide range of applicability. The main attention is paid to substantiation of the method, its properties, and its verification in numerical and laboratory experiments. The method is recommended for measuring the losses of composite highly damped oscillatory systems, where known methods do not work or are too complex.

Reducing noise in the cabin of propeller aircraft is an urgent problem of internal acoustics, since traditional sound-insulating structures are insufficiently effective in the low-frequency region. One promising method for solving it is to use resonance systems, with which it is possible to significantly increase the sound insulation of the fuselage structure of aircraft in this frequency range. The study determined the effect of resonance systems on the sound-insulating ability of flat and cylindrical panels without and with cross stiffening simulating the body bulkhead frame was experimentally determined, as well as the effectiveness of facing the passenger compartment with resonance systems with different compositions. Tests were carried out in sound chambers and on a full-scale bench, which is a real passenger plane. The tested structures were faced with elastoacoustic compensators of various types with resonance elements made of foil, micalent paper, and thermopolyurethane. It is shown that the efficiency of resonance systems can reach 10–20 dB or more.

The propagation of torsional waves through rods with a variable cross section is considered. When the flattening of a rod is linearly increased, the propagation velocity of a torsional wave also linearly decreases to become zero at a finite rod length. Meanwhile, the time of propagation to the sharpened end is equal to infinity. In contemporary terminology, such a decelerating structure is called a vibrational black hole. Exact solutions are found for the equations of torsional vibrations in a sharpened rod with an inertia moment and a torsion moment in the form of power functions along with corresponding expressions for the input impedance at the initial cross section.

Using numerical modeling based on mode theory and the geometric-acoustic approximation, it was determined that in addition to classical quadruples of pulses present in the spatiotemporal field structure, the emergence of additional signals with relatively short delays is caused by the formation of weakly divergent multimode beams in the underwater sound channel of the Sea of Japan; these modes correspond to smooth extrema in the dependences of the spatial interference period of neighboring modes and their group velocity on the mode number. For one of the two sound speed profiles typical of the Sea of Japan, it was shown that at relatively high frequencies, it is possible to receive two groups of additional signals: weakly divergent beams formed by relatively low- and high-order modes.

A technique for correcting the fields detected by an array with nonideal placement of transmitting and receiving transducers has been developed and numerically tested. The displacements of the transducers from their ideal positions are preliminarily determined. The correction technique involves finding the angular harmonics based on the fields measured with the displaced transducers. Then these found angular harmonics make it possible to recalculate the fields at ideal positions of the transducers, as well as directly calculate the scattering amplitude. Such corrected data is the input one for the stage of reconstruction of acoustic tomograms, i.e., the internal structure of an object. Numerical simulation has been used to show that in the absence of the correction of the data measured in real conditions, the tomograms can be fractured.