Abstract：The non-periodic structure’s dispersion equation and the sound attenuation equation have been given based on the one-dimensional model of sound propagation. The relationship between the geometry parameters of drill strings with the dispersion characteristic as well as the attenuation characteristic is investigated numerically for a non-periodic drill string system, and the FEM software- ANSYS were used to confirm the theory results. The results shows that the dispersion characteristic of a non-periodic drill string system is identical with the result from of 'and' operation of dispersion characteristic of multiple periodic structure systems．The non-periodic structure’ passband is narrow while the stopband is wide, If the sound wave frequency were in the stopband, the acoustic attenuation would be larger than it in passband.
2012, Vol. 31 
