Identification of Boundary Conditions Using Natural Frequencies in Case   of a Ring Membrane
  The problem of finding boundary conditions for fastening of a ring membrane, which are inaccessible for direct observation from the natural frequencies of its flexural oscillations, is considered. Two theorems on the uniqueness of this problem are proved, and a method for establishing the unknown conditions for fastening of the membrane to the walls is indicated. An approximate formula for determining the unknown conditions is obtained, using first three natural frequencies. The method of approximate calculation of unknown boundary conditions, is explained with the help of an example. Keywords: Boundary conditions, inverse spectral problem, membrane, natural frequencies, Plucker coordinates, Plucker relation. 
A. M. Akhtymov, A. V. Mouftakhov, M. Teicher