The possibility of global noise reduction by the sound power control is discussed. It is necessary to investigate the relation between the global sound energy in the field and the total sound power radiated by sources. In the previous work [1,2], the authors presented a useful design method to change boundary condition that reduces noise in acoustically small enclosures. Changing boundary condition is related to not only its geometrical shape but also acoustical treatment on walls; for example, attaching of impedance patches (ex: absorptive material). In many practical situations, we often meet a situation to change acoustical treatment on walls. A paper related to what we envisaged was presented at Inter-noise 2003 (S.-H. Cho, Y.-H. Kim, and K. Grosh, “The effect of impedance patch position on the sound field of an acoustically small cavity,” in Proc. Inter-noise 2003, N236). In this paper, the relation between acoustic source power control and global noise reduction are discussed. The possibility of total acoustic potential energy, which is global noise, reduction by acoustic source power control is examined for acoustically small cavity. Using acoustic energy balance equation, the relation between global noise control performance and absorptive material arrangement is deduced. Simulation is performed to investigate the theoretical possibility and the power control trend in terms of total acoustic potential energy reduction with respect to the frequency range of interest.