The paper presents the experimental results concerning the dynamical behavior of ligno-cellulose composite plates with different stiffening braces. Two types of tests were performed: non-contact test (with acoustic excitation) and contact method (with mechanical vibrations of mini-shaker). Within the first part of the paper, the methods and the types of the studied plates are depicted. Within the second part, the results of the experimental research studies namely the modal shapes (Fig. 1. Chladni pattern), the Fourier analysis and the power spectrum density are presented. The identification of dynamic behavior of each type of plate aims the optimization of stiffening structure of plates in accordance with the desired resonance frequencies.