Acoustical Physics最新文献

Abstract

The normal mode method is widely employed for addressing depth-dependent acoustic wave propagation, with its accuracy contingent upon the precision of the propagating wavenumbers and depth mode shapes. Typically, finite-difference and finite-element methods are utilized for such solutions. Recently, a new approach has been proposed for heterogeneous depth-dependent waveguides, utilizing the classical Rayleigh–Ritz (RR) method. This method demonstrates high accuracy from low-frequency to high-frequency ranges. However, the matrices involved for solving the eigenvalue problems necessitate numerical integrations for evaluating each element, resulting in increased computational costs. To mitigate this, a similar method (RRF) is proposed, where sound speed profiles are expressed as a sum of Fourier series. This allows for the analytical computation of each entry of the RR matrices but compromises the accuracy of the wavenumbers. This paper presents a novel technique aimed at enhancing the precision of determining wavenumbers and mode shapes, while simultaneously minimizing the computational effort without compromising the accuracy. The method involves discretizing sound speed profiles using piecewise linear functions and deriving closed-form solutions for RR matrix elements, while also accounting for sound speed attenuation. Various examples are examined to evaluate the proposed method, demonstrating its capability to compute propagating radial wavenumbers with significantly improved accuracy and reduced computational cost, often achieving improvements of one or two orders of magnitude. Additionally, comparisons of transmission losses at fixed depth indicate accuracy comparable to existing solutions, without any noticeable visual discrepancies.

The study compares the capabilities of using 3D acoustic models of the human head, constructed using magnetic resonance imaging (MRI) and computed tomography (CT) data, to simulate ultrasound beam focusing when passing through skull bones and to compensate for aberrations caused by them. A CT and MRI dataset from one patient was considered. The MRI data were used to reconstruct segments of the human head (skin, skull, and brain) that were homogeneous in their internal structure. The most realistic CT model took into account the internal inhomogeneities of the skull bones and soft tissues. Field simulations and compensation for aberrations were performed using the Rayleigh integral and pseudospectral method for solving the wave equation in an inhomogeneous medium, implemented in the k-Wave software package. The transducer was considered to be a fully populated 256-element phased array with a frequency of 1 MHz and radius of curvature and an aperture of 200 mm. It was shown that when aberrations were compensated using an inhomogeneous CT model and a homogeneous MRI model, the pressure amplitude at the focus and focusing efficiency were different by less than 10%. Thus, a homogeneous MRI model can be used for preoperative assessment of the feasibility of transcranial ultrasound therapy. During therapy, it is preferable to take into account the internal structure of the skull bones based on CT data.

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.

Abstract

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.

Abstract

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.

An array consisting of three sensors was used for correlation measurements of thermal acoustic radiation. For the first time, all cross-correlation functions were obtained for each pair of sensors. The measurements were carried out at two positions of the source (a heated narrow Teflon cylinder), the distance between which was equal to half the spatial period of the cross-correlation function of adjacent sensors. The measured correlation functions were in antiphase, which corresponds to the calculated correlation functions of thermal acoustic radiation. To pass from correlation functions to temperature distribution, spatial cross-correlation functions for adjacent and the outermost sensors in the array are summed. The correlation methodology makes it possible to significantly increase the spatial resolution of the method.

Abstract

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 0.19 λ was obtained.

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 an laser device are presented.

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.

The problem of sound propagation in a cylindrical duct with a uniform flow is considered with nonlinear impedance boundary conditions resulting from the dependence of the impedance of acoustic liners on the sound pressure level. An iterative procedure for solving this problem has been constructed, in which sound propagation is described by an asymptotic solution to the problem of the propagation of sound modes in a cylindrical duct with a uniform flow with a smoothly non-uniform impedance of the walls in the axial direction, and the nonlinear mode of operation of the liners is based on a semiempirical model of a two-layer acoustic liners. It is shown that the constructed iterative algorithm converges within the limits of applicability of the asymptotic solution and diverges beyond them. It is shown that, for the parameters with which the calculations were carried out, the nonlinear effect of the liners operation leads to an increase in sound attenuation compared to a linear solution of a similar problem, and this effect is when sound propagates along rather than against the flow.