Analyses and assessment of the sensitivity of trim parameters on SEA simulation for interior noise reduction

To predict and analyse the acoustical behaviour of complex structures at higher frequencies
the field of deterministic analysis methods like FEM or BEM has to be left. In this paper the
energy based statistical approach called Statistical Energy Analysis (SEA) is used.
To optimize acoustic packages of vehicles a definition of interior equipment (trim) in SEA
models is required. One possibility is to use absorption, damping and insertion loss as
parameters for the modelling of each trim part. Using this definition all different trim parts
can be described through the same type of parameters, which is a big advantage of this rather
abstract approach.
In defining optimal acoustic packages for vehicles, engineers face many problems. Definition
of acoustic packages is extremely time critical and changes of the geometry of the vehicle
have to be avoided in the development process. Furthermore, acoustic packages are limited
by weight and cost requirements.
Having knowledge about areas, where a change of trim behaviour has a large influence on the
sound pressure level (SPL) in the passenger compartment, is extremely helpful during
defining acoustical packages. To provide this information a method using a mathematical
sensitivity analysis had been developed. This method computes influences of trim parameters
(absorption, damping and insertion loss) of different trim parts on the SPL. A detailed
description of this method and its mathematical background will be given in this paper.
Through principle examples the developed method will be illustrated and verification will be
done using a full vehicle model. Application of a mathematical optimization, which is based
on this method, will be a scope of future work