Haleylynch9312

The approach is numerically validated by comparison with a detailed room model, where random wave scatterers are explicitly modeled as acoustic point masses with random positions, and good correspondence is observed. Furthermore, applications involving correlated sound sources and sound-structure interaction are presented.The presence of a boundary produces marked changes in the oscillation amplitudes and types of bubble distortion modes excited by an external acoustic field. In the majority of cases, the radiation force can be determined based on the linearized equations of motion. Bispherical coordinates are used to obtain an analytical description of linearized bubble dynamics at distances from the interface comparable to those of the bubble size. In the limit of weak dissipation, explicit formulas have been derived that describe the dependence of the radiation force on the separation distance between the bubble and the interface, the material parameters of the contacting media, and the angle of incidence of the incoming wave. The component of the radiation force directed to the interface has been shown to exhibit qualitative changes when the direction of the incoming field passes through the angle of the total internal reflection.The exponential sine sweep is a commonly used excitation signal in acoustic measurements, which, however, is susceptible to non-stationary noise. This paper shows how to detect contaminated sweep signals and select clean ones based on a procedure called the rule of two, which analyzes repeated sweep measurements. A high correlation between a pair of signals indicates that they are devoid of non-stationary noise. The detection threshold for the correlation is determined based on the energy of background noise and time variance. Not being disturbed by non-stationary events, a median-based method is suggested for reliable background noise energy estimation. The proposed method is shown to detect reliably 95% of impulsive noises and 75% of dropouts in the synthesized sweeps. Tested on a large set of measurements and compared with a previous method, the proposed method is shown to be more robust in detecting various non-stationary disturbances, improving the detection rate by 30 percentage points. The rule-of-two procedure increases the robustness of practical acoustic and audio measurements.Volumetric wave-based simulation methods for room and virtual acoustics, such as the finite difference time domain method, are computationally intensive; for large volumes, operation over a regular grid is desirable for the sake of efficiency. In coping with realistic irregular geometries (such as enclosures or scattering objects), form-fitting meshing can disturb grid regularity and introduce new difficulties in terms of maintaining numerical stability. An alternative is the immersed boundary method, allowing for the representation of an irregular boundary over a regular grid through additional forcing terms in the dynamical system. While heavily used in fluid-structure interaction problems, such methods have seen less application in virtual acoustics. In this article, a simplified form of the immersed boundary method tailored to virtual acoustics is presented. Under appropriate passivity-preserving discretisation techniques, simple numerical stability conditions can be proved, and in particular, impedance boundaries may be incorporated easily without any risk of numerical instability. In addition, the method retains a largely explicit character with a small linear system solution required over the immersed boundary surface. Numerical results in two and three dimensions, illustrating various interior and exterior problem scenarios, are presented.Globally, noise exposure from occupational and nonoccupational sources is common, and, as a result, noise-induced hearing loss affects tens of millions of people. Occupational noise exposures have been studied and regulated for decades, but nonoccupational sound exposures are not well understood. The nationwide Apple Hearing Study, launched using the Apple research app in November 2019 (Apple Inc., Cupertino, CA), is characterizing the levels at which participants listen to headphone audio content, as well as their listening habits. This paper describes the methods of the study, which collects data from several types of hearing tests and uses the Apple Watch noise app to measure environmental sound levels and cardiovascular metrics. Participants, all of whom have consented to participate and share their data, have already contributed nearly 300 × 106 h of sound measurements and 200 000 hearing assessments. The preliminary results indicate that environmental sound levels have been higher, on average, than headphone audio, about 10% of the participants have a diagnosed hearing loss, and nearly 20% of the participants have hearing difficulty. The study's analyses will promote understanding of the overall exposures to sound and associated impacts on hearing and cardiovascular health. This study also demonstrates the feasibility of collecting clinically relevant exposure and health data outside of traditional research settings.Conventional flextensional transducers possess advantages of low frequency, small dimension, and high power [K. D. Rolt, J. Acoust. Soc. Am. 87, 1340 (1990)]. The low-frequency circular array composed of flextensional transducers has a strong mutual radiation effect due to the large vibration amplitude of the radiation surface located inside the circular array and the close distance between array elements [Z. Y. He et al., AIP Conf. Proc. 1272, 345 (2010)]. Here, a single-sided radiation flextensional transducer (SSR FT) is designed for a low-frequency circular close-packed array to diminish the mutual radiation effect. On the basis of the vibration principle of SSR FT, effects of structural parameters on electroacoustic, vibration, and radiation performance are studied for the final design of the transducer. Subsequently, the mutual radiation effect of circular close-packed arrays composed of SSR FTs and their counterparts is qualitatively analyzed on the basis of resonant mass, equivalent circuit, and numerical simulations. Finally, fabricated and tested circular arrays lead to a conclusion that the circular array composed of SSR FTs has a weaker mutual radiation effect and smaller dimensions than its counterpart composed of class IV FTs [K. P. B. Moosad, G. Chandrashekar, M. J. Joseph, and R. John, Appl. Acoust. 72, 127-131 (2011)]. The results confirm that the circular close-packed array provides flexibility in the application of low-frequency and small-dimension underwater acoustic sources.The high-performance and aberration-free broadband acoustic lens holds promise for extensive applications, yet remains challenged. In this work, a scheme is proposed, and the experimental demonstration of a planar acoustic Luneburg lens capable of focusing broadband sound ranging from 1 to 3 kHz (relative bandwidth approaching to 100%) in an aberration-free manner is presented. Concretely, plane sound within the frequency range incident from one side can be concentrated on a same point on the opposite edge of the Luneburg lens. The demanded refractive indexes of the lens are obtained from the component space coil acoustic metamaterials, which can easily manipulate the refractive index by adjusting a structural parameter. The prototype of the proposed Luneburg lens is fabricated by three-dimensional printing technology and experimentally characterized in a two-dimensional acoustic measuring platform. The measured results are consistently in good agreement with those from the numerical simulations. Pidnarulex research buy Finally, the proposed Luneburg lens is employed to construct a wide-angle acoustic reflector, which can produce a strong echo propagating in the direction exactly opposite to the incident wave. These results facilitate potential possibilities for developing more acoustic functional devices capable of manipulating broadband sound.Focused ultrasound treatments of the spinal cord may be facilitated using a phased array transducer and beamforming to correct spine-induced focal aberrations. Simulations can non-invasively calculate aberration corrections using x-ray computed tomography (CT) data that are correlated to density (ρ) and longitudinal sound speed (cL). We aimed to optimize vertebral lamina-specific cL(ρ) functions at a physiological temperature (37 °C) to maximize time domain simulation accuracy. Odd-numbered ex vivo human thoracic vertebrae were imaged with a clinical CT-scanner (0.511 × 0.511 × 0.5 mm), then sonicated with a transducer (514 kHz) focused on the canal via the vertebral lamina. Vertebra-induced signal time shifts were extracted from pressure waveforms recorded within the canals. Measurements were repeated 5× per vertebra, with 2.5 mm vertical vertebra shifts between measurements. Linear functions relating cL with CT-derived density were optimized. The optimized function was cL(ρ)=0.35(ρ-ρw)+ cL,w m/s, where w denotes water, giving the tested laminae a mean bulk density of 1600 ± 30 kg/m3 and a mean bulk cL of 1670 ± 60 m/s. The optimized lamina cL(ρ) function was accurate to λ/16 when implemented in a multi-layered ray acoustics model. This modelling accuracy will improve trans-spine ultrasound beamforming.The eigenfunctions of the Laplace-Beltrami operator have widespread applications in a number of disciplines of engineering, computer vision/graphics, machine learning, etc. These eigenfunctions or manifold harmonics (MHs) provide the means to smoothly interpolate data on a manifold and are highly effective, specifically as it relates to geometry representation and editing; MHs form a natural basis for multi-resolution representation (and editing) of complex surfaces and functions defined therein. In this paper, we seek to develop the framework to exploit the benefits of MHs for shape reconstruction. To this end, a highly compressible, multi-resolution shape reconstruction scheme using MHs is developed. The method relies on subdivision basis sets to construct boundary element isogeometric methods for analysis and surface finite elements to construct MHs. This technique is paired with the volumetric source reconstruction method to determine an initial starting point. The examples presented highlight efficacy of the approach in the presence of noisy data, including a significant reduction in the number of degrees of freedom for complex objects, accuracy of reconstruction, and multi-resolution capabilities.In this work, solitary wave solutions of particle mechanical metamaterials are studied, in which the mass-in-mass structure with local resonators is considered. The Hertzian contact theory is used to describe adjacent particles in a precompressed granular chain. The governing wave equations are decoupled, and the expressions of bright, dark, and peaked solitary waves are derived, respectively. According to the results, both the wave velocity and prestress can affect the propagation of solitary waves. The amplitudes of bright and peaked solitary waves are smaller when a larger prestress is applied, which are different from the dark solitons. Furthermore, the wave widths become larger as the prestress increases.