Bakushinsky B., Leonov A.S. «Modeling the Solution of the Acoustic Inverse Problem of Scattering for a Three-Dimensional Nonstationary Medium» Acoustical Physics, 70, № 1, с. 153-164 (2024)

The inverse problem of acoustic sounding of a three-dimensional nonstationary medium is considered, based on the Cauchy problem for the wave equation with a sound speed coefficient depending on the spatial coordinates and time. The data in the inverse problem are measurements of time-dependent acoustic pressure in some spatial domain. Using these data, it is necessary to determine the positions of local acoustic inhomogeneities (spatial sound speed distributions), which change over time. A special idealized sounding model is used, in which, in particular, it is assumed that the spatial sound speed distribution changes little in the interval between source time pulses. With such a model, the inverse problem is reduced to solving three-dimensional Fredholm linear integral equations for each sounding time interval. Using these solutions, the spatial sound speed distributions are calculated in each sounding time interval. When a special (plane-layer) geometric scheme for the location of the observation and sounding domains is included in the sounding scheme, the inverse problem can be reduced to solving systems of one-dimensional linear Fredholm integral equations, which are solved by well-known methods for regularizing ill-posed problems. This makes it possible to solve the three-dimensional inverse problem of determining the nonstationary sound speed distribution in the sounded medium on a personal computer of average performance for fairly detailed spatial grids in a few minutes. The efficiency of the corresponding algorithm for solving a three-dimensional nonstationary inverse sounding problem in the case of moving local acoustic inhomogeneities is illustrated by solving a number of model problems.

Liu S., Li M., Zhao R. «The Sound Source Location Based on Phase Conjugation and Acoustic Superlens» Acoustical Physics, 70, № 1, с. 58-67 (2024)

In order to break through the diffraction limit of traditional sound sources, an idea of far-field super-resolution imaging based on acoustic superlens is proposed, that is, acoustic super-lens is used to transmit near-field sound field information to the far-field, and far-field super-resolution imaging is realized by combining phase conjugate algorithm. In this paper, the sound source localization effect of the two-dimensional honeycomb acoustic superlens of water/mercury material is systematically studied, and the sub-wavelength imaging with a resolution of 0.22λ is obtained by simulating the point sound source imaging through numerical simulation, and the imaging principle of the refractive index n=–1 configuration is explained by combining the imaging principle of flat lens imaging and the law of refraction. A multi-lens was designed for far-field localization of point sound sources, and sub-wavelength imaging with a resolution of 0.19λ was obtained.

Zhang E.L., Peng Z.L., Li Z.J., Lin Y.B., Zhuo J.M. «Four-Channel Active Noise Control Modeling and Offline Simulation for Electric Bus Sound Quality Based on Two FxLMS Algorithms» Acoustical Physics, 70, № 1, с. 143-152 (2024)

Aiming at the consensus problem of slow convergence for the active noise control (ANC) model based on standard FxLMS algorithm that leads to performance degradation, this paper takes the error signal and its variation as the inputs of fuzzy logic control, and proposes an improved FxLMS algorithm by fuzzy control mechanism with two-input-two-output TSK fuzzy rules (TSK-FxLMS); In addition, the four-channel ANC models based on standard FxLMS and TSK-FxLMS are constructed using the noise signals from four measuring points inside an electric bus under uniform and variable speed conditions, respectively. Ultimately, the offline simulation and acoustic parameter calculation results indicate that the A-weighted sound pressure level (ASPL) and loudness of the two FxLMS models within the low and middle frequencies are significantly reduced, whereas the TSK-FxLMS model has faster convergence rate, higher average reduction percentage of ASPL and loudness, which proves that the established four-channel TSK-FxLMS model has a better sound quality improvement effect than the standard FxLMS.

Zhang E.L., Peng Z.L., Li Z.J., Lin Y.B., Zhuo J.M. «Four-Channel Active Noise Control Modeling and Offline Simulation for Electric Bus Sound Quality Based on Two FxLMS Algorithms» Acoustical Physics, 70, № 1, с. 143-152 (2024)

Aiming at the consensus problem of slow convergence for the active noise control (ANC) model based on standard FxLMS algorithm that leads to performance degradation, this paper takes the error signal and its variation as the inputs of fuzzy logic control, and proposes an improved FxLMS algorithm by fuzzy control mechanism with two-input-two-output TSK fuzzy rules (TSK-FxLMS); In addition, the four-channel ANC models based on standard FxLMS and TSK-FxLMS are constructed using the noise signals from four measuring points inside an electric bus under uniform and variable speed conditions, respectively. Ultimately, the offline simulation and acoustic parameter calculation results indicate that the A-weighted sound pressure level (ASPL) and loudness of the two FxLMS models within the low and middle frequencies are significantly reduced, whereas the TSK-FxLMS model has faster convergence rate, higher average reduction percentage of ASPL and loudness, which proves that the established four-channel TSK-FxLMS model has a better sound quality improvement effect than the standard FxLMS.

Liu S., Li M., Zhao R. «The Sound Source Location Based on Phase Conjugation and Acoustic Superlens» Acoustical Physics, 70, № 1, с. 58-67 (2024)

In order to break through the diffraction limit of traditional sound sources, an idea of far-field super-resolution imaging based on acoustic superlens is proposed, that is, acoustic super-lens is used to transmit near-field sound field information to the far-field, and far-field super-resolution imaging is realized by combining phase conjugate algorithm. In this paper, the sound source localization effect of the two-dimensional honeycomb acoustic superlens of water/mercury material is systematically studied, and the sub-wavelength imaging with a resolution of 0.22λ is obtained by simulating the point sound source imaging through numerical simulation, and the imaging principle of the refractive index n=–1 configuration is explained by combining the imaging principle of flat lens imaging and the law of refraction. A multi-lens was designed for far-field localization of point sound sources, and sub-wavelength imaging with a resolution of 0.19λ was obtained.

Bai Yunshan, Liu Yuanxue, Gao Guangjian, Cui Dandan, Chen Han «Estimating the Azimuth of Acoustic Emission Source in Concrete Plate-Like Structures using a Non-Contact Sensor Unit» Acoustical Physics, 70, № 1, с. 130-142 (2024)

Location of damage sources is an important aspect of structural health monitoring research. Acoustic emission (AE) technology is broadly concerned due to its potential advantages in damage monitoring and source localization. However, the traditional positioning method is based on the arrival of P wave, and the non-uniformity of concrete materials is not considered, resulting in poor accuracy at large distances. This paper describes a non-contact AE localization method using leaky Rayleigh waves via a new air-coupled MEMS microphones array unit. Compared with traditional contact detection, this method is convenient for rapid setup and monitoring in a wider range. The feasibility of the non-contact AE localization method was verified by numerical simulation and experiments. Azimuth (direction of arrival) of AE source is a key source parameter for damage location. The research shows that this method can determine the azimuth of AE source at different positions, the results are close to the actual coordinates. Non-contact monitoring method proposed in this paper is the basis for further research on the failure prediction of concrete plate-like structures such as tunnel lining and bridge deck.