The present disclosure relates to a method of creating a propellant mixture. The method includes forming an explosive composition mixture, placing the explosive composition mixture into a mixing vessel assembly, and operating an acoustic mixing system at an operating frequency such that the acoustic mixing system causes a vertical displacement of the mixing vessel. The explosive composition mixture has an explosive material, and one or more additives. The mixing vessel assembly has a closed mixing zone having a maximum vertical height. The acoustic mixing system is operated in a manner such that the operating frequency is substantially similar to the resonant frequency and a ratio of the maximum vertical height of the closed mixing zone to the vertical displacement of the mixing vessel assembly is 2.0 or less.