Acoustic impedance of a folded rectangular cross shape cavity

Accurate estimation of the acoustics impedance of a folded cavity is important for predicting its sound absorption performance. In this paper, the effect caused by a right angle sharp bend on the acoustic impedance of a folded cavity with rectangular cross section is investigated by comparing the sound absorption coefficients for the folded cavities to the straight ducts with same length and cross section area. Based on the simulation results, a corrected parameter is proposed to calculate the equivalent geometries for the right bend by dividing the cavity into folded and straight sections. The experiment results confirm the feasibility of the proposed formula.