Short Notes K8 1 phys. stat. sol. (b) 133, K81 (1986) Subject classification: 62.65 and 77.50 Instituto Venezolano de Investigaciones C i e n t k c a s (NIC), Centro de Ffsica, Caracas1) The Effect of Energy Conservation Surface Overlap Breakdown on the Low-Temperature Ultrasonic Attenuation in DielectricsThe absorption of high frequency acoustic waves in dielectrics at low tempera t u r e s when 1;24 >> 1, where ! 2 is the ultrasonic frequency and < is the mean thermal phonon relaxation time, is explained by three-phonon anharmonic N-