Good Matching Broad-band Frequency Acoustic Duct Lined with Parabolic Increasing Microperforated Area
Fathy B. Shenoda, M. Y.El Aidy · Journal of Engineering Science and Technology Review · 2024
Despite the increasing interest in acoustic silencer design for various noise control applications, the good matching performance duct design has not been getting much interest.The present work gives the theoretical study and the experimental verification of the matching performance to plane sound waves in a one-dimensional duct lined with a parabolic increasing microperforated area.The wave propagation inside the duct is modelled using the boundary element method (BEM), and its solution is derived using the modified Hankel function.The matching performance, namely the wave impedance, and the sound reflection coefficient at the duct inlet were computed when this duct is inserted between two similar hard ducts.Ducts lined with different duct parameters of length, cross-section diameter, graduality of the wall conductance of different micro-perforation characteristic parameters were considered.The wave impedance and the sound reflection coefficient of a single slit treatment, at the duct inlet were theoretically studied and discussed.Also, ducts of multiple treatments by equal and similar slit areas of micro-perforation were studied.The theoretical study of the proposed duct design shows that the matching performance can be improved by tuning both duct parameters and MPP liner physical characteristics, especially for liners in which the reactive part of its impedance is less or equal to its resistive part, and a reflection coefficient of less than 0.15 which is the reflection-free condition, is obtained in a wideband frequency from low frequency, from 200 Hz to the first high mode frequency in the duct.In comparing the theoretical and experimental measurement data, a reasonable agreement has been found for both the sound impedance and the sound reflection at the duct inlet.