The sound generation mechanism of “singing ferrites”is studied，and the resonant frequency，displacement and stress distribution of the ferrite rods with free edges under the condition of bias magnetic field are calculated based on the longitudinal vibration theory and the linear magnetostrictive constitutive equations． The longitudinal vibration modes，resonant frequencies and the relation between amplitude and voltage of the three ferrite rods are tested．Experimental tests on rods show that the amplitude is approximately linear with the voltage within a certain bias magnetic field and a certain excitation voltage． Ultrasonic atomization will occur when the amplitude is greater than 1 μm． At the excitation voltage of 65 V，the amplitude can reach 16 μm， meanwhile the rod will break．The breakpoint position is basically consistent with that of the calculation．