Alexander Peiffer

• Dr.-Ing. Dipl. phys
• Head of team BEV acoustics and active systems at Audi AG

Vibroacoustic simulation is the discipline of modelling and predicting the acoustic waves and vibration of particular objects, systems, or structures. This is done through finite element methods (FEM) or statistical energy analysis (SEA) to cover the full frequency range. In the mid-frequency range, both methods must be combined into a hybrid FEM/S...

Beams or shells were characterized by their boundaries, but their effect was the creation of different forms of wave propagation. A one‐dimensional subsystem can be a small tube with radius 𝑅 small enough that the wavelength is larger than the diameter 2𝑅 for the highest considered frequency. Continuous and bounded systems have modes and natural sh...

The first step in SEA modelling is to find a realistic description of the subsystems by a diffuse wave field. Wavenumber, group wave speed, and geometry provide the modal density. The understanding of the coupling phenomena is very important for noise control in general. Some of the examples for coupling loss factors are useful for practical purpos...

The twin chamber set‐up is such a perfect example for the hybrid method, because both chambers are designed to be random by the large size and irregular shape. So, the two cavities can be considered as random subsystems for the complete frequency range. The hybrid method destroys the diagonal form of the dynamic stiffness matrix. Though the introdu...

Simple systems with properties constructed by lumped elements as masses, springs and dampers are a good playground to understand and investigate the physics of dynamic systems. Critically damped systems can be of practical relevance, because the motion returns to rest in the shortest possible time, which is useful if periodic motion shall be preven...

The random description of vibroacoustic systems is well suited for large and complex systems with high Helmhotz number. This chapter explains the principle procedures to perform a SEA simulation, the way of subsystem description, and the determination of the coupling loss factor on realistic examples. Due to the statistic nature of the reverberant...

This chapter provides some literature proposals of advanced experimental methods that are required to provide test results that can be used in model updates. The transfer path analysis is based on the measurement of the frequency transfer function of vibroacoustic systems. The experimental SEA can be considered as a transfer path analysis of random...

In technical acoustics, deterministic systems are usually treated by numeric methods like the finite element method or the boundary element method. Those methods require complex and powerful solvers as far as pre and post‐processors to handle large and detailed models. One‐dimensional acoustic elements are used in the simulation of mufflers, ventil...

The degrees of freedom of the coupling zone are shared, and the state variables, for example pressure and displacement, are equal. Simulating the coupling dynamics can become a complicated task even for pure deterministic subsystems. In practical vibroacoustics, deterministic systems are rarely described by continuous coordinates but discrete coord...

The complex situation of wave propagation in structures becomes even worse for closed structural systems. When specific features like holes, rigs, beading or any complicated shape is given, this is definitely the world of numerical methods. Current finite element methods in combination with pre and post processors can handle very complex and large...

All real engineering systems are subject to uncertainty. The response of the dynamic system becomes very uncertain and varies strongly. In dynamically complex systems the uncertainty and the multiple reflections of waves will constitude a wave field created by multiple waves with random phases. This initiates the concept of diffuse field where the...

This chapter summarizes the studies in such a way that the concepts of wave propagation in typical structural systems can be applied for the wave field descriptions. In fluids the state variable of the wave equation was the pressure. The relationship between the strain and stress tensors is given by the material laws called Hooke's law for linear e...

This chapter is about industrial examples dealing with practical and complex cases. The models rely on commercial software tools, namely NASTRAN™ for pure FE models or VAOne™ from ESI‐Group and Wave™ from Dassault Systems as hybrid finite element method/SEA solvers. All software tools have various materials, properties, and subsystem formulations i...

The acoustic wave motion is described by the equations of aerodynamics that are linearized because of the small fluctuations that occur in acoustic waves compared to the static state variables. The fluid motion is described generally by three equations: Continuity equation – conservation of mass; Newton's law – conservation of momentum; and state l...

The excitation of structures by turbulent boundary layer requires the consideration of the cross-spectral density for all degrees of freedom excited by the pressure fluctuations. This leads to large and computationally expensive matrices for the calculation of the structural response or even radiation into the fluid. This paper deals with the compa...

In the application of Statistical Energy Analysis “SEA” to complex assembled structures, a purely predictive model often exhibits errors. These errors are mainly due to a lack of accurate modelling of the power transmission mechanism described through the Coupling Loss Factors (CLF). Experimental SEA (ESEA) is practically used by the automotive and...

This paper deals with the overall simulation strategy in the aerospace context. Here used for interior noise prediction, acoustic design, optimisation of noise control and support to test interpretation. There are specific characteristics resulting from the aerospace context but many aspects are similar for other means of transportation as trains,...

The major part of the acoustic mid-frequency power flow into cabins of aircraft, trains or cars is transmitted via double wall systems. Especially the double wall effect is a typical example for hybrid theory because of the deterministic nature of the double wall resonance. In hybrid theory implementations deterministic subsystems are modelled usin...

The aim of this paper is to present the applicability of the average beamforming (ABF) as a helpful technique to map acoustic emission for interior noise in which we can assume that sources exist only on the wall, but not in the internal volume.In these conditions conventional beamforming measurements show disturbing pseudo-sources in the acoustic...

The Elastodynamic Finite Integration Technique (EFIT), originally developed by Fellinger et al.,1–3 represents a stable and efficient numerical code to model elastic wave propagation in linearly-elastic isotropic and anisotropic, homogeneous and heterogeneous as well as dissipative and nondissipative media. In previous works, the FIT discretization...

The modeling of interior noise requires the application of so called hybrid methods. One reason for the application of hybrid methods is that in the mid frequency regime some components of the aircraft must be modeled by discrete methods like the finite element method (FEM) others can be modeled by the statistical energy analysis (SEA). One typical...

New complex materials constitute new challenges for the well established nondestructive ultrasonic testing (UT) methods. In aeronautic industry Carbon Fiber Reinforced Plastics (CFRP) with a high level of inner inhomogeneity are used. New construction methods of these materials lead to manufacturing problems that cannot be monitored satisfactorily...

The straightforward finite element modelling of the structural response due to random excitation requires either the determination of the full scale frequency response matrix or the modal joint acceptance function in real space. Both methods are unfeasible due the computational load even for small structures. One solution to overcome this situation...

To simulate ultrasonic inspection of modern materials both an appropriate simulation method and a powerful tool to generate the models have to be provided. Therefore, the Elastodynamic Finite Integration Technique (EFIT) is combined with the software module WiseTex from the Katholieke Universiteit Leuven in Belgium. This paper presents the modellin...

The Elastodynamic Finite Integration Technique (EFIT) is a numerical method to simulate the propagation of ultrasonic waves through complex material structures. In this paper the simulation method is applied to composite laminate materials. The detailed microstructure models of the laminate specimens are generated by the software module WiseTex fro...

Sandwichstrukturen gewinnen aufgrund ihres niedrigen spezifischen Gewichts bezogen auf die Biegesteifigkeit des Materials immer mehr an Bedeutung im Bereich der Luft- und Raumfahrtanwendungen. Für eine akustische Bewer-tung dieser Strukturen ist die Berechnung des Schall¬dämm-Maßes bezogen auf eine Diffusfeldanregung sehr gut geeignet. Zu diesem Zw...

Bei der Berechnung des Schalldurchgangs durch Wandstrukturen wird entweder eine Kombination von FEM- und BEM-Verfahren eingesetzt [1] oder FEM Verfahren unter Verwendung von Infiniten Elementen. Diese Methoden sind insbesondere für Diffusfeldanregung über mehrere Frequenzschritte sehr zeitaufwändig. Dazu wurde unter der Vorraussetzung schwacher Kop...

This report deals with the design of an active vibration control (AVC) system integrated into the primary suspension of the bogie of a German high-speed train (ICE). As a design case a prototype bogie (WU92) for the ICE2 was taken. This paper comprises all parts and stages of the development of an AVC system. First, a transfer path analysis was per...

Strong research efforts have been made during the last decades on actively controlled mechanic systems also called smart structures in case that a high degree of integration for sensors, actuators, control electronics and mechanical structures is achieved. These technologies enable and inspire radical breakthroughs in product performance, which is...

Several work proceeded at the Fraunhofer Institute IZFP/EADQ Dresden on photo and particle acoustic methods is reviewed. It includes both modelling activities and experimental work. The range of applied excitations covers photons, electrons and high energy (hundreds of MeV/amu) ions. Both time resolved measurements by pulse excitation as well as mo...

In the present paper, a new version of the elastodynamic finite integration technique for axisymmetric wave propagation in homogeneous and heterogeneous linear elastic media (CEFIT) is presented. This special variant of a finite difference time domain scheme offers a suitable method to calculate real three-dimensional problems in a two-dimensional...

In der Schwerionentherapie wird im Gegensatz zur klassischen Strahlentherapie keine harte Röntgenstrahlung verwendet, sondern sogenannte schwere Ionen, zum Beispiel: Kohlenstoff. Diese deponieren fast den gesamten Anteil ihrer Energie in einer definierten Tiefe in einem Bereich von wenigen Millimetern. Diese präzise Therapieform verlangt aber eine...

This paper deals with the elastodynamic finite integration technique for axisymmetric wave propagation in a homogeneous and heterogeneous cylindrical medium (CEFIT). This special variant of a finite difference time domain (FDTD) scheme offers a suitable method to calculate real three-dimensional problems in a two-dimensional staggered grid. In orde...

Many ultrasonic nondestructive testing applications have cylindrical geometries. Examples involve the excitation of ultrasound by cylindrical piezoelectic probes or by laser, x rays, electron beams [A. C. Tam, Rev. Mod. Phys. 58, 381–431 (1986)], or ion beams [L. Sulak et al., Nucl. Instrum. Methods 161, 203–217 (1979)]. Thus, calculations of cylin...

Ionenakustische Schallquellen treten bei Anwendungen auf, in denen Ionenstrahlen auf Festkörper oder Fluide treffen. Dies ist bei allen Prozessen der Fall, in denen Ionenstrahlen als flexibles Werkzeug eingesetzt werden. Beispiele betreffen Ionenfeinstrahlanlagen oder die Tumortherapie mit relativistischen Kohlenstoffionen. In dieser Arbeit werden...