The formula for acoustic length correction of perforated tube muffler

The formulas of acoustic length correction and resonance frequency of perforated tube muffler are derived.It is proved that in the case of uniform distribution,the acoustic length correction coefficient of the acoustic radiation from multiple holes to cavity is consistent with that from a single hole to cavity.For the acoustic radiation from the holes to the main pipe,the effects of perforation porosity,circumferential uniform number and Helmholtz number on the acoustic length correction are studied according to the formula.Resultsshow that the theoretical formula of acoustic length correction coefficient is in good agreement with the simulation results when the diameter radio is less than 0.4.A practical fitting formula is obtained by using the properties of the theoretical formula and the simulation results.The calculation accuracy of resonance frequency of perforated tube muffler at high frequency is improved.