The working principle of electromagnetic buzzer: AC signal generates alternating flux on the core pillar of the support through the wire wrapped on the support. The alternating flux and the constant flux of the magnetic ring are superimposed to make the molybdenum sheet vibrate at a given AC signal frequency and cooperate with the resonant cavity to produce sound. The response curve of the whole frequency and sound pressure of the product is directly related to the gap value, the natural vibration frequency of the molybdenum sheet (which can be roughly refracted as the thickness of the small molybdenum sheet), the shell (Helmholtz resonant cavity) frequency, and the diameter of the magnetic enameled wire of the magnetic ring.