This paper aims to investigate the consequences of faults in a mechanical system on sound perception. Because of mechanical variability affecting its structure, an object resulting from an industrial production can exhibit an important variability in its vibratory and acoustical behavior. However, are the main characteritics of the object timbre conserved? A dispersive physical model, on which structural uncertainties were simulated, was set up for sound synthesis. The "emitted" sound was the assessed by a group of listeners performing two different tasks. These tests enabled to determine which uncertainties did affect sound perception, as the way they were perceived bt the listeners.