Photoacoustic (PA) observation of the decay channels of surface plasmons wag made on the plasmong excited by the attenuated total reflection (ATE). Both in the interfaces of Ag-air and CaF2-Ag-air, ATR and PA spectrum were measured at the game time. The results show that it is possible to determine the radiative and non-radiative decay quantatively by comparing measurements taken with transparent and blackened cavities.