In this paper, an approximate method for calculating the resonance frequency of anexponential horn is proposed. Using the principle of equal mass, the exponential horn is approximated as a cylindrical bar. Frequency equations for flexural vibration are derivedbased onboth Euler-Bernoulli theory and Timoshenko theory. The first three resonance frequencies of flexural vibration are calculated using Pythonforboth theoriesand are compared with resultsobtained via the finite element method (FEM). Theproposedapproximate method is shown to be suitable for calculating the resonance frequency of anexponential horn, providedthat the difference in radius between its two ends is minimal.