Elastic properties of the filled skutterudite compound SmOs4Sb12 have been investigated by ultrasonic measurements. The elastic constant C11(ω) shows two ultrasonic dispersions at ∼15 and ∼53 K for frequencies ω between 33 and 316 MHz, which follow a Debye-type formula with Arrhenius-type temperaturedependent relaxation times and remain unchanged even with applied magnetic fields up to 10 T. The corresponding activation energies were estimated to be E2 = 105 K and E1 = 409 K, respectively. The latter, E1, is the highest value reported thus far in the Sb-based filled skutterudites. The prese...