Date Approved

6-30-2025

Embargo Period

6-30-2025

Document Type

Thesis

Degree Name

M.S. Mechanical Engineering

Department

Mechanical Engineering

College

Henry M. Rowan College of Engineering

Advisor

Chen Shen, Ph.D.

Committee Member 1

Antonios Kontsos, Ph.D.

Committee Member 2

Yashwant Sinha, Ph.D.

Keywords

Acoustic Muffler;Broadband Attenuation;Duct Silencer;Metamaterial;Space-Folded;Transmission Loss

Abstract

Control and reduction of unwanted noise is a significant concern in many residential, commercial, and industrial fields. Specifically, ducted noise control is of increasing importance due to the complex challenges of ventilation requirements imposed on the system. This research presents a compact, space-folded silencer which achieves broadband attenuation of noise in ducted applications. Making use of axial arrays of side- loaded resonators, this structure allows for unobstructed fluid-flow through its center, resulting in a static fluid pressure drop across the device of only 14.5 Pa. In addition, due to the silencer’s configurable nature, the geometry can be tuned to meet acoustic and geometric requirements during the design. Using theoretical calculations based upon the Transfer Matrix Method, a structure has been parametrically optimized to maximize acoustic transmission loss (TL) from 650 Hz to 2000 Hz. Experimental testing of the optimized silencer under stationary conditions resulted an average TL of 36.3 dB between 650 Hz and 2000 Hz, and experimental testing under grazing flow resulted in an average TL of 17.2 dB. In addition, numerical analysis of the structure was carried out under a mean grazing flow and a linear correlation was found between fluid-flow velocity and normalized change in transmission loss.

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