Noise control study in building acoustics with flexible-absorbent duct

The indoor quiet environment in modern buildings is a persistent challenge, especially due to the noise produced by mechanical devices such as “heating, ventilation and air-conditioned” (HVAC) systems or other exhaust purposes. The aim of the current study is to address these challenges by exploring the use of flexible-absorbent acoustic duct within building acoustic mechanisms. The flexible nature of the duct is designed with elastic membrane walls at inlet and outlet sections, whilst fibrous and perforated absorbent materials are coated with horizontal walls of the expansion chamber of the duct to minimize noise and vibrations effectively. The Mode-Matching (MM) method provides a solution to the underlying issue by utilizing Helmholtz’s field equation with prescribed boundary constraints. Eigenvalues are computed through numerical experiments based on the governed dispersion relations. The complexity of higher-order membrane boundaries renders traditional orthogonality relations (OR) inadequate, leading to the development of generalized orthogonality relations. Graphical representations reveal how acoustic power scattering varies across different frequencies for varying duct configurations, including impedance, fibrous, and perforated sheets for both fundamental and secondary born mode incidents. The validation process, based on power conservation principles, showcases both the accuracy and convergence of the computational model by comparing results graphically and in tabular form, providing strong evidence of the duct’s efficiency in minimizing noise. Thus, the current study not only enhances noise reduction in internal mechanical acoustic systems but can also improve building acoustics overall. •Attenuation of acoustic wave in flexible bifurcated waveguide by varying different material properties.•Fibrous and perforated porous lining materials are incorporated in the expansion chamber of a waveguide structure.•Matching conditions and implication of edge conditions are assured the uniqueness of the physical model.•Energy conservation law and matching conditions ensure the accuracy of obtained algebra and numerical results.•Resulting infinite algebraic equations are solved numerically and obtained results are graphically analyzed.