 but even in this case—if acoustic-elastic coupling and internal dissipations of the membrane are taken into account—the problem remains delicatem, and results must be verified experimentally.However, even in the absence of a solution, it is possible to note that decay of the partials is connected with the merit factor (Q) of their resonance, and provokes a widening of the spectral line—always more marked the more the relative mode is damped.The internal frictions are proportional to the velocity of variation of the local curvature, which increases with the frequency.