Noise reduction through a waveguide structure consisting of expansion chambers with a geometrical defect

Laboratory of Materials, Waves, Energy and Environment, Faculty of Sciences, Oujda 60000, Morocco

^* Corresponding author: ilyasantraoui@gmail.com

Abstract

Noise control helps to make working environments safer and keep operations in line with health and safety standards. Exhaust noise is the main component of noise pollution in urban environments. In this paper, we focus on noise control by improving acoustic attenuation performance using a one-dimensional waveguide structure composed of simple periodic expansion chambers with a geometric defect. This defect is located at the center of the periodic structure and results from a modification in the length of the central chamber of the system. The objective is to study the properties of acoustic transmission and transmission loss and to examine the effect of defects in a periodic acoustic structure. The system’s spatial periodicity enables us to design wide band gaps where sound waves cannot propagate. This characteristic is very important for reducing noise in our environment. The effect of the cross-sectional ratio on the band gap behavior was also examined in this work. In addition, we have shown that the presence of a defect in a regular structure leads to a perturbation of the structure’s spatial periodicity. This leads to the creation of defect modes or resonance modes in the band gaps. We also controlled the number and amplitude of defect peaks within the band gap by varying the length of the defect. The results of this work are of interest for various applications, such as the creation of wide acoustic bands, low-frequency noise reduction, and acoustic wave filtering.