The Finite Strip Method for Acoustic and Vibroacoustic Problems

Journal of Sound and Vibration

2016

A model for the prediction of direct and indirect (flanking) sound transmissions is presented. It can be applied to geometries with extrusion symmetry. The structures are modelled with spectral finite elements. The acoustic domains are described by means of a modal expansion of the pressure field and must be cuboid-shaped. These reasonable simplifications in the geometry allow the use of more efficient numerical methods. Consequently the coupled vibroacoustic problem in structures such as junctions is efficiently solved.\ud The vibration reduction index of T-junctions with acoustic excitation and with point force excitation is compared. The differences due to the excitation type obey quite general trends that could be taken into account by prediction formulas. However, they are smaller than other uncertainties not considered in practice. The model is also used to check if the sound transmissions of a fully vibroacoustic problem involving several flanking paths can be reproduced by superposition of independent paths. There exist some differences caused by the interaction between paths, which are more important at low frequencies.Peer ReviewedPostprint (author's final draft

Section: Numerical Results and Analysismentioning

confidence: 99%

“…FSM can exactly reproduce these limitations in order to make a fair comparison. For this reason, the FSM [49] is chosen in order to compare the combination of modalspectral interpolation with an element-based approach. The treatment of the Ydirection is the same in both models while the difference relies on the X − Z plane.…”

Section: Comparison With the Fsmmentioning

confidence: 99%

A modal-spectral model for flanking transmissions

Journal of Sound and Vibration

2016

“…In other modelling techniques the output assigned to each cell can be a simple average of the solution. For example, the vibroacoustic problems of Section 4.3 have been solved by means of the finite strip method [22]. The vibration and pressure fields in the three-dimensional space are obtained as a combination of spatial discrete interpolation in a problem section and a modal combination in the third dimension.…”

Section: The Cluster Elementsmentioning

confidence: 99%

“…Therefore, the dimension of the space is equal to the number of eigenmodes considered. These modes are computed with the finite element code Cast3M [23] for vibratory problems and with an in-house code based on the finite strip method for vibroacoustic problems [22]. The eigenmodes of the problem are good samples for the cluster analysis, because each of them provides an independent and significant case to analyse.…”

Section: The Sample Spacementioning

confidence: 99%

Automatic subsystem identification in statistical energy analysis

Díaz-Cereceda

Mechanical Systems and Signal Processing

Ferran

2015

An automatic methodology for identifying SEA (statistical energy analysis) subsystems within a vibroacoustic system is presented. It consists in dividing the system into cells and grouping them into subsystems via a hierarchical cluster analysis based on the problem eigenmodes. The subsystem distribution corresponds to the optimal grouping of the cells, which is defined in terms of the correlation distance between them. The main advantages of this methodology are its automatic performance and its applicability both to vibratory and vibroacoustic systems. Moreover, the method allows the definition of more than one subsystem in the same geometrical region when required. This is the case of eigenmodes with a very different mechanical response (e.g. out-of-plane or in-plane vibration in shells).

“…The idea is similar to that of the finite strip method but this one is particularly suitable for multilayered structures because it allows the resolution of the Helmholtz equation at each layer, taking into account the continuity of the normal velocity at their interfaces. Moreover, due to the use of trigonometric functions in the in-plane directions, its computational cost is significantly lower than that of pure finite element analysis [34].…”

Section: Introductionmentioning

confidence: 99%

The finite layer method for modelling the sound transmission through double walls

Díaz-Cereceda

Journal of Sound and Vibration

Ferran

2012

The finite layer method (FLM) is presented as a discretisation technique for the computation of noise transmission through double walls. It combines a finite element method (FEM) discretisation in the direction perpendicular to the wall with trigonometric functions in the two in-plane directions. It is used for solving the Helmholtz equation at the cavity inside the double wall, while the wall leaves are modelled with the thin plate equation and solved with modal analysis. Other approaches to this problem are described here (and adapted where needed) in order to compare them with the FLM. They range from impedance models of the double wall behaviour to different numerical methods for solving the Helmholtz equation in the cavity. For the examples simulated in this work (impact noise and airborne sound transmission), the former are less accurate than the latter at low frequencies. The main advantage of FLM over the other discretisation techniques is the possibility of extending it to multilayered structures without changing the interpolation functions and with an affordable computational cost. This potential is illustrated with a calculation of the noise transmission through a multilayered structure: a double wall partially filled with absorbing material.