Proper orthogonal decomposition (POD) is a powerful technique for model reduction of nonlinear systems. It is based on a Galerkin type discretization with basis elements created from the nonlinear system itself. In this paper an identification problem arising in car vehicle acoustics is considered. To estimate the impedance from point-wise sound pressure values the identification problem is formulated in terms of an optimal control problem, which is solved by a globalized quasi-Newton method. For the efficient and fast numerical realization, a POD based model reduction is utilized.