关键词: 汽笛发声, 圆膜, 自由振动, 频谱分析, 基频

Abstract: Based on the theoretical study of free vibration of plane film，combined with the Eighth National College Physics academic competition，the phenomenon of sound vibration of the whistle is studied. According to the free vibration equation of the circular film，the different modes of the circular film vibration are analyzed by using the Bessel function. We make the 3D printing technology to make different specifications of the whistle. The circular tube changes the experimental condition，we use a high-speed camera to record the vibration process of the circular film，and use the Audacity software to analyze the fundamental frequency of the circular film vibration. The quantitative study of the vibration of the circular film is realized. The results show that the size of the tension of the circular film in the vibration is the choice of the vibration mode in the linear interval of the elastic deformation of the circular film. The main factor is that in the same vibration mode，changing the length and inner diameter of the whistle tube has no effect on the vibration form.

Key words: whistle sound, circular film, free vibration, spectrum analysis, fundamental frequency