Theoretical explanation of the ‘local resonance’ in stepped acoustic horn based on Four-End Network method

By using Four-End Network method, the ‘local resonance’ frequency equation of stepped horn can be deduced from the resonance frequency equation of conical composite horn, and the formula to calculate the stress in stepped horn is obtained. According to the results of finite element analysis (FEA) on stepped horn, the ‘local resonance’ phenomenon is caused by the abrupt change of section area, and, correspondingly, high stress concentration. It is shown that section area ratio is closely related to the ‘local resonance’ frequency.