Sonic crystal green walls based on a combination of cylinder scatterers and vegetation for noise mitigation in urban design

Abstract

This study proposes sonic crystal green walls based on combined cylinder scatterers and vegetation. It has been known that the vegetation or greenery system is effective in dealing with environmental pollutants, while the cylinder scatterer arranged periodically, also known as a sonic crystal, is preferable owing to the capability of noise attenuation, light transmission, and air circulation simultaneously. Combining both components into a single noise abatement system is expected to provide acoustical and non-acoustical features for urban design, where such an approach maximizes the merit of each component. Moreover, the system is useful for advocating sustainability amid global warming issues. In this work, a numerical model is developed using finite element method (FEM), while experimental results are provided to validate the absorption and attenuation results. It is found that the sonic crystal can attain an attenuation of 13.5 dB around 1.6 kHz. Such a promising result is extended further to lower frequency under a specific configuration of scatterers corresponding to lattice distance and filling faction ratio parameters. Meanwhile, the vegetation can enhance overall attenuation at higher frequencies.