The new preventive passive low-frequency acoustical method of nondestructive testing of the energetic bladed systems is considered. The proposed method is based on reception, processing, and estimation of parameters of the energetic bladed system's own acoustic noise in a low-frequency range (0.002--50 kHz) with the usage information about rotation frequencies of rotors. The method includes the following procedures: (1) detection of the narrow-band acoustic signals on the background of interference; (2) identification of the detected acoustic signals; and (3) estimation of testing date and decision acceptance of the state of the energetic bladed system stages. The method allows for acceptance of the state at the appropriate stage of the energetic system in maintenance when the stage is in a normal state, or when the stage is in a state before damage. Experimental results are presented. The proposed method represents one of the approaches to efficient energy use and conservation.