Membrane-type electromagnetic acoustic sources have the advantages of large volume displacement，controllable ultra-low frequency acoustic field and good adaptability，so they have broad application prospect in the field of minesweeping acoustic source. Radiation membrane is the core vibration component of an acoustic source. It is of great significance to study the vibration characteristics of radiation membrane for the design and application of electromagnetic acoustic sources. In this paper，an analytical method for the vibration characteristics of an electromagnetic acoustic source with membrane structure is studied. Firstly，the analytical model of the free vibration of the circular membrane of the electromagnetic acoustic source in vacuum is established. Secondly，the natural frequencies and modes of free vibration of the circular membrane in vacuum are obtained using the method of separation of variables. The correctness of theoretical solution is verified by comparing the calculated natural frequencies with the data in the references as well as finite element simulation. Then，the influence of different boundary conditions and the change of the radius of the circular membrane on the vibration characteristics of the membrane in vacuum is analyzed. Finally，considering the influence of viscous liquid loads and internal filling pressure，the amplitude-frequency characteristics and volume-displacement of the low frequency forced vibration of the circular membrane with different sizes in actual working conditions of the electromagnetic acoustic source are obtained. The method presented in this paper can accurately reflect the vibration characteristics and acoustic radiation capacity of the electromagnetic acoustic source under actual working conditions，and can provide an important reference for the design and structural optimization of high-power electromagnetic acoustic source.
