École Nationale Supérieure de
Techniques Avancées

Abstract

It has been experimentally shown that the shape and the materials of loudspeaker membranes have an influence on sound reproduction. From those observations the present thesis aims at modeling the nonlinear behavior of loudspeakers subjected to large amplitude motions over the audible bandwidth (including electrical and geometrical nonlinearities). The first part describes a theoretical approach of the influence of materials and shape on the vibration pattern of an idealized loudspeaker. The dynamic analog of the Von-Kármán equations is used and the solutions are projected over the linear modes of the structure. The second part proposes a resolution scheme of the electromechanical couplings using the state space formalism. The problem is first developed in the case of an unique mode of vibration and then extended including resonance modes and geometrical nonlinearities of the structure. In the third part, a time-domain approach of the radiation problem based on the Rayleigh integral is proposed. The method uses the Spatial Impulse Response technique which allow to reduce calculation costs directly in the time-domain. Finally, the present approach is applied in the case of a prototype developed at the LAUM by Guy Lemarquand. A good agreement between measurements and predictions using the present model can be achieved and the influence of geometrical nonlinearities on sound radiation is discussed.