This paper deals with the extraction of wave features in elastic media. An inverse approach is proposed for the identification of wave dispersion characteristics (e.g. k-space) in one- and ...two-dimensional structures (1D, 2D). The proposed method is similar to the ESPRIT algorithm and the Prony series method and can be considered as an extension of the latter, specifically when applied to 1D problems. By using a convolution framework, the method is extended to the 2D case for which it allows the estimation of the full k-space by solving a linear problem. The method is called INverse COnvolution MEthod (INCOME). The formulation of INCOME is first detailed and mathematically justified. Both the 1D and 2D cases are detailed and explained. Then several examples are presented for assessing the validity domain of INCOME. These numerical tests clearly show the relevance of INCOME for structured inputs with periodic characteristics.
•We introduce a new wavenumber extraction method for 1D and 2D wave propagation.•The proposed method is exact in both 1D and 2D cases.•In the 2D case, a full continuous k-space is retrieved in a coherent manner.•The proposed technique resembles the WFEM and can be considered an inverse WFEM.
About the conferenceInternational Conference for Acoustic and Vibration Engineers (NVHH 2023) is the first edition of the biennial NVHH conference series on acoustics, structural dynamics and NVH ...(Noise Vibration and Harshness) organized by the Budapest University of Technology and Economics, the University of Győr, and the Hungarian Chamber of Engineers in close cooperation with industrial partners. The goal of the conference is to provide an international forum for acoustic, vibration, and NVH engineers, researchers, and professionals to share their contributions in the fields of experimental as well as numerical acoustics, vibroacoustics, vehicle NVH, interior acoustics, and entertainment system development. The conference caters to both academicians and professionals, therefore state-of-the-art university research and cutting-edge industrial innovation will be presented side by side, followed by social gatherings that promote the exchange of information and nurture fruitful cooperations between the various fields of the profession.NVHH 2023 in numbersThe conference hosted 112 participants from 9 European countries, presenting 38 technical or scientific papers in 8 sessions, complemented by 4 plenary lectures. 9 professional exhibitors contributed to the industrial relevance.List of Conference Chairs, Keynote and plenary lectures, Organizing Committee, Scientific Committee are available in this Pdf.
The Acoustic Black Hole (ABH) is a technique for passive vibration control that was recently developed within the Structural Dynamics and Vibroacoustics communities. From a general perspective, the ...ABH effect is achieved by embedding a local inhomogeneity in a thin-walled structure, typically a beam or a plate. This inhomogeneity is characterized by a variation of the geometric properties (although material variations are also possible) according to a spatial power law profile. The combination of a local stiffness reduction, due to the power law variation of the wall thickness, and of a local increase in damping, provided by the concurrent application of viscoelastic layers, gives rise to a significant reduction of the wave speed and to a remarkable enhancement of the attenuation properties. As an elastic wave travels within an ABH, its speed experiences a smooth and continuous decrease. In the ideal case, that is when the wall thickness vanishes at the ABH center, the wave speed decreases to zero. In the non-ideal case, that is when the ABH has a non-zero residual thickness at its center, the wave speed still decreases smoothly but it never vanishes. In this latter case, which is of great importance for practical applications, the ABH is typically combined with lossy media (e.g. viscoelastic layers) in order to achieve significantly enhanced structural loss factors. If the speed of an incoming wave can vanish inside the ABH, it follows that this object behaves as a wave trap that extracts elastic energy from the host medium without, in principle, ever releasing it. Several characteristic properties are generally observed in structures with embedded ABHs: significant reduction in vibration and acoustic radiation levels, low reflection coefficient at the ABH location, localized vibration and trapped modes, and existence of cut-on frequencies. Contrarily to passive vibration methods based on viscoelastic materials, the ABH was developed and applied to reduce vibrations and structure-radiated noise without increasing the total mass of the system. More recently, applications to other areas including elastic metastructures, energy harvesting, vibro-impact systems, and cochlear systems were also investigated. This review is intended to provide a comprehensive summary of the state-of-the-art of ABH technology, spanning from theoretical and numerical contributions to practical applications.
Dispersion and scattering properties of a soft solid plate with solid cylindrical inclusions embedded in are theoretically and numerically reported in this work. The system is numerically analyzed ...considering both the vibroacoustic coupling and the presence of viscoelastic losses. In addition to the mechanical properties of the soft solid plate that allows the shift of the higher order Lamb modes to the low audible frequency domain, the presence of the inclusions introduces resonant and antiresonant phenomena in the subwavelength regime, leading to an elastic band-gap and a destructive modal interference in the soft solid plate able to interact with each other. These phenomena are used to design a system with strong transmission loss, breaking the mass law by 15 dB, and with subwavelength dimensions as the thickness is 32 times smaller than the equivalent wavelength in air. These performances are both computed and tested experimentally using a standard measuring process.
•Soft solid material can be used to design low-frequency sound insulator.•Soft solid subwavelength plate with periodic inclusions overcomes the mass-law.•A destructive interference exists between the rigid body mode and a periodicity mode.•A band-gap and a destructive interference lead to a low acoustic transmission area.
Recently, metamaterials, sandwich panels, and a combination of both have shown potential for creating lightweight, load-bearing structures with good noise and vibration suppression properties. ...However, designing these structures is difficult due to the complex vibroacoustic innate physics and the need to balance conflicting requirements. Structural optimization methods can help address this multi-functional, multi-physical design challenge. While much research has been conducted on optimizing the materials and sizes of plates and sandwich cores, the systematic topological design of fully coupled vibroacoustic cores has not yet been explored. To address this gap, this work presents a topology optimization framework for the vibroacoustic design of sandwich structure cores, with the goal of minimizing sound transmission while constraining volume and structural stiffness. The framework is used to conduct a systematic design analysis, focusing on the dynamic behavior of the optimized structures. The versatility of the methodology is demonstrated by analyzing different targeted frequency ranges, different angles of incidence and the trade-off between the acoustic and structural performance. The resulting designs are lightweight, load-bearing, and achieve high sound transmission loss performance, exceeding the mass law by 15−40 dB in targeted frequency ranges of 500Hz in the interval between 1000Hz and 3000Hz.
•Systematic design analysis of sandwich structures is presented.•Topology optimization framework proposed for sound transmission minimization.•Vibroacoustic coupling considered in the optimization design space.•Trade-off between structural, acoustic and mass requirements investigated.•Versatility of framework shown by several numerical studies.
The prediction of the vibrational response of a structure subjected to an aerodynamic load is fundamental for assessing preliminary structural design and addressing typical structural problems such ...as fatigue and structure-borne sound. In literature, there are already alternative experimental methods capable of reproducing the response to a TBL excitation without using wind tunnel facilities. One of them is the eXperimental Pseudo-Equivalent Deterministic Excitation method (X-PEDEM). The method has only been numerically validated; therefore, with the present work, it is wanted to experimentally test X-PEDEM by conducting a hammer impact test on three different panels, for different boundary conditions and for different asymptotic flow velocities. X-PEDEM demonstrates that is able to reproduce, in an approximate manner, the reference solutions for all aforementioned cases, ensuring an optimal accuracy for frequencies far from the convective coincidence frequency.
•Pre-design experiments can improve the design process of structures under airflow.•The structural response to aerodynamic load is reproducible without wind tunnels.•The presented methodology uses an impact test and a fast post-processing phase.•It guarantees the versatility for different structures and boundary conditions.•The structural response is reproduced in a broadband frequency range.
The combination of experimental and numerical data is a typical challenge in complex vibro-acoustic problems. Rather than employing model-updating techniques, we combine the modal substructuring ...technique with non-conforming grids in order to be able to directly employ experimental and numerical modes for the description of weakly coupled vibro-acoustic systems. By incorporating Delaunay triangulation in the process, mechanical modes of any origin and discretized in terms of point clouds can be coupled with computational acoustic modes. The method is validated using a two-sided vibro-acoustic box. It is demonstrated that, by employing suitable interpolation techniques, systems based on coarsely discretized experimental modes can be used analogously to computational modes. The approach makes it straightforward to take into account modal damping and to fit numerical modes via experimental modal parameters, such as eigenfrequency, modal mass and damping.
•Structural modes from modal analysis can be coupled with computational acoustic modes.•Simple implementation for complex grids by employing point clouds and Delaunay triangulation.•Interpolation techniques allow to use low-res scattered measurement points.•Coupled vibro-acoustic modes can be derived from uncoupled modes.•Thin-plate spline interpolation significantly reduces coupling errors.
The numerical investigation of acoustic damping materials, such as foams, constitutes a valuable enhancement to experimental testing. Typically, such materials are modeled in a homogenized way in ...order to reduce the computational effort and to circumvent the need for a computational mesh that resolves the complex micro-structure. However, to gain detailed insight into the acoustic behavior, e.g., the transmittance of noise, such fully resolved models are mandatory. The meshing process can still be drastically simplified by using a fictitious domain approach. We propose the finite cell method, which combines the fictitious domain approach with high-order finite elements and resolves the complex geometry using special quadrature rules. In order to take into account the fluid-filled pores of a typical damping material, a coupled vibroacoustic problem needs to be solved. To this end, we construct two separate finite cell discretizations and prescribe coupling conditions at the interface in the usual manner. The only difference to a classical boundary fitted approach to vibroacoustics is that the fluid-solid interface is immersed into the respective discretization and does not correspond to the element boundaries. The proposed enhancement of the finite cell method for vibroacoustics is verified based on a comparison with commercial software and used within an exemplary application.
•The finite cell method (FCM) is applied to vibroacoustics for the first time.•Two superimposed Cartesian grids are employed for the fluid and the structure domain.•The discretization approach is verified by a comparison with commercial software.•An exemplary application motivates fully resolved simulations of acoustic foams.•The simulation pipeline can be used as is for geometries based in CT scans.
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