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Currently, the use of numerical and analytical tools during a vehicle development is extensive in the automotive industry. This assures that the required performance levels can be achieved from the early stages of development. However, there are some aspects of the vibro-acoustic performance of a vehicle that are rarely assessed through numerical or analytical analysis. An example is the modeling of sound transmission through vehicle sealing systems. In this case, most of the investigations have been done experimentally, and the analytical models available are not sufficiently accurate. In this paper, the modeling of the sound transmission through a vehicle door seal is presented. The study is an extension of a previous work in which the applicability of the Hybrid FE-SEA method was demonstrated for predicting the TL of sealing elements.

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.

Statistical Energy Analysis (SEA) is the standard method used to access noise and vibration levels in aircrafts and it has been applied to a wide range of problems in the aerospace industry. Even though much research has been carried on in the subject, some questions still remain about the process of modeling aircraft structures and the necessary validation steps. In this work, the development of a SEA model of a fuselage section is discussed. Special attention is given to the structure-borne noise transmission between the fuselage and floor panels and different modeling approaches are investigated. Data obtained through experimental tests were then used to verify the modeling approaches. It is seen that overall SEA results display a good agreement with tests. In the case of the floor panel, model results are very sensitive to modeling approaches and given that the transmission path is correctly represented, the SEA results reasonably match the experimental data.

The Hybrid FE-SEA method is a recently developed numerical technique that deals with the so-called mid-frequency problem. Such problems involve the dynamic analysis of systems that include, at the same frequency range, components with high and low modal density. Systems with a reduced number of modes are usually modeled using deterministic methods, as the Finite Element (FE) Method, while modal dense systems need to be treated by means of statistical methods such as the Statistical Energy Analysis (SEA). Neither FE nor SEA can properly describe a system that displays the mid-frequency behavior due to a prohibitive computational cost (FE) or the lack of accuracy (SEA). The floor structure of an aircraft is a typical case of a mid frequency problem, where the floor beams are relatively rigid and have very few modes while the floor panels have a very high modal density.

In recent years, SEA has been recognized as an important tool to model the vibro-acoustic behavior of vehicles in mid and high frequencies. Through SEA it is possible to develop vehicle models early in the design stage, reducing the risk of future noise problems and allowing the optimization of noise control treatments. Moreover, at the final design stages, a SEA model can be use to evaluate changes at the project, reducing costs with experiments. In a SEA model, the structure under study is divided in subsystems. The capacity of each subsystem of storekeeping, dissipating and transmitting energy is described by three parameters: modal density, loss factor and coupling loss factor. The noise and vibration sources are include in the model as power inputs to subsystem and, based on an equilibrium power balance, it is possible to calculate the energy of each subsystem.

The Statistical Energy Analysis – SEA is one of the main methods used to study the vibro-acoustic behavior of systems in the aeronautic, automotive and naval industries. The principal advantages of this method are the possibility of analysis in the mid and high frequencies range, the reduced computational costs when compared with other methods (like Finite Element Method or Boundary Element Method) and ease modeling of different sources of noise and vibration. As a statistical method, SEA provides results associated with average values in time, space and in an ensemble of similar structures. In aerospace applications, where the noise and vibration sources are usually random, SEA is particularly indicated. SEA also allows the straightforward modeling of the noise control treatments used in commercial aircraft and the further optimization of these treatments, reducing weight and costs. In this work, the steps followed at the development of an EMBRAER aircraft SEA model are presented.