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Aero-vibro-acoustic prediction of interior noise associated with exterior flow requires accurate predictions of both fluctuating surface pressures across the exterior of a vehicle and efficient models of the vibro-acoustic transmission of these surface pressures to the interior of a vehicle. The simulation strategy used in this paper combines both CFD and vibro-acoustic methods. An accurate excitation field (which accounts for both hydrodynamic and acoustic pressure fluctuations) is calculated with a hybrid CAA approach based on an incompressible unsteady flow field with an additional acoustic wave equation. To obtain the interior noise level at the driver's ears a vibro-acoustic model is used to calculate the response of the structure and interior cavities. The aero-vibro-acoustic simulation strategy is demonstrated for a Mercedes-Benz S-class and the predictions are compared to experimental wind tunnel measurements.

Prediction of flow induced noise in the interior of a passenger car requires accurate representations of both fluctuating surface pressures across the exterior of the vehicle and efficient models of the vibro-acoustic transmission of these surface pressures to the driver’s ear. In this paper, aeroacoustic and vibro-acoustic methods are combined in order to perform an aero-vibro-acoustic analysis of a Mercedes-Benz A-class. The exterior aero-acoustic method consists of a time domain incompressible Detached Eddy Simulation (DES) and an acoustic wave equation. The method is extended in this paper to account for convection effects when modelling the exterior sound propagation. The interior vibro-acoustic model consists of a frequency domain Finite Element (FE) model of the side glass combined with a generalized Statistical Energy Analysis (SEA) model of the interior cabin.

Noise transmission paths in an aircraft include, in many cases, both components with a few modes and others with a high modal density. The components with few modes display a long wavelength behavior and are usually modeled using the Finite Element Method (FEM). On the other hand, components with many modes show a short wavelength behavior and suit the application of the Statistical Energy Analysis (SEA). An example of this kind of transmission path is given by the vibration transmission from the fuselage to the floor panels through the floor beams. The fuselage and the floor panels possess a high modal density while the floor beams are considerably stiff and display a small number of modes. The prediction of the vibro-acoustic response of such systems is commonly called the “mid frequency problem” and, until recently, was difficult to be handled with traditional modeling approaches. A Hybrid method that rigorously couples SEA and FEM has been recently proposed.

Seals and slits are often an important transmission path for vehicle interior noise at mid and high frequencies, and they are therefore often included in system level SEA models of interior noise. The transmission loss of seals and slits in such models is typically either measured experimentally or predicted using simple analytical models. The problem with the former is that it is expensive to investigate different design options using test; the problem with the latter is that simple analytical models often do not contain enough detail. The objective of this paper is therefore to investigate how much detail is needed in order to predict the transmission loss of typical slits and seals. Typical door seals are not directly exposed to exterior and interior sound fields, but instead are inserted in complicated “channel” sections formed by the door and pillar or rail structures. This study is therefore divided in two parts.

During the last decades, the application of noise control treatments in vehicles has targeted the main noise transmission paths to interior noise. These paths include vehicle body panels such as dash panel, doors and floor. Many improvements have been achieved on these areas, and, as a consequence, other transmission paths once thought as secondary became relevant. This is the case of the sound transmission through door seals and others sealing elements at mid and high frequencies. In this paper, the interest lies on the prediction of the transmission loss of door seals. A full nonlinear deformation/contact analysis is used to estimate the deformed geometry of a door seal in real conditions. The geometry is then used in a vibro-acoustic analysis to predict the in-situ transmission loss of the seal using a local Hybrid FE-SEA model. The channel between the door and the car structure where the seal is located is also included in the analysis.

There are many applications in which exterior flow over a structure is an important source for interior noise. In order to predict interior “wind noise” it is necessary to model both: (i) the spatial and spectral statistics of the exterior fluctuating surface pressures (across a broad frequency range) and (ii) the way in which these fluctuating surface pressures are transmitted through a structure and radiated as interior noise (across a broad frequency range). One approach to the former is to use an unsteady CFD model. While CFD is used routinely for external aerodynamics, its application to the characterization of exterior fluctuating surface pressures for broadband interior noise problems is relatively new. Accurate prediction of both the convective and acoustic wavenumber content of the flow across a broad frequency range can therefore present some challenges.

A hybrid FE-SEA analysis method has been developed to predict the structural response of complex systems at mid and high frequencies. At these frequencies, the dynamic properties of some components might be very sensitive to small perturbations while other components might exhibit a very robust behavior. This mixed dynamic behavior precludes the use of fully statistical approaches like SEA [1] or fully deterministic approaches like FE. In the hybrid method, either an SEA or an FE model is applied to each component of the complex system, and both descriptions are rigorously coupled in a generic way. An overview of the method is presented along with numerical and experimental validation studies.

Automotive interior noise at mid and high frequencies is typically dominated by the airborne noise from acoustic sources that are spatially distributed around a vehicle. Each source is typically spatially compact (for example, a tire contact patch) but the source radiates sound that then propagates across the entire exterior surface of the vehicle. To characterize a source it is therefore necessary to know both the sound pressure level in the vicinity of the source and also the way in which sound from the source diffracts around the vehicle. The former depends on the details of the source, the latter typically depends on the overall vehicle geometry. When creating Statistical Energy Analysis (SEA) models of interior noise, the diffraction of airborne loads around a vehicle is often measured experimentally.