APPLICATION OF THE CONCEPT OF ACOUSTIC INFLUENCE COEFFICIENTS FOR THEOPTIMIZATION OF A VEHICLE ROOF

To improve the acoustic behaviour of vehicles is an increasing challen ge for every car manufacturer. The sound pressure at the drivers ear d ue to an arbitrary excitation of the structure can be calculated by a harmonic analysis first of the structure and then of the fluid. Using the concept of influence coefficients one has to carry out the harmoni c analysis of the fluid only once to determine the sound pressure at t he drivers ear. If the influence coefficients are available one has to solve an easy algebraic relation instead of a full harmonic analysis. This requires that geometry modifications are small compared with the acoustic wave lengths. So, the computational expenditure is mainly co nfined to the harmonic analysis of the structure. In this paper, the p rincipal way of carrying out an optimization of a vehicle body is pres ented for the example of a vehicle roof. The parametric geometry based model of the roof is time harmonically excited. All other parts of th e body are considered to remain rigid. Admittance boundary conditions are included. Results are presented for different loads and frequency domains, for limited and for unlimited permissible variations of the g eometry and for different modal dampings. (C) 1998 Elsevier Science Lt d. All rights reserved.