The ultrasonic attenuation of low temperature peaks in the PdD_(.67) has been studied. The peak is seen only for longitudinal waves, not for transverse ones, and it is observed only in the deuterides, not in the hydrides. The low temperature peak is correlated with relaxation phenomenon due to redistribution of LO phonons by ultrasonic waves. Ultrasonic attenuation of the PdD_(.67)H_(.02) sample was measured to see the influence of hydrogen in the PdD_(.67); the low temperature peaks of the PdD_(.67)H_(.02) and the PdD_(.67) do not show significant, difference within the limit of experimental error. Ultrasonic attenuations of the PdD_x(x=0.64-0.72) are decreased as the deutrium concentration increased.