COMPUTATIONAL STUDY OF THE USE OF FRACTAL ACOUSTIC DIFFUSERS IN NOISE BARRIERS

Abstract

This thesis investigates the improvements in the predicted acoustical performance of barriers that can be obtained by incorporating a series of quarter-wavelength resonators, and both one- and two-dimensional sound diffusers. Incorporating fractal and nested sound diffusers on the top-edge of noise barriers improved the overall noise attenuation for both 1D and 2D diffusers. The aim was to achieve controlled scattering and redirection of incident sound by increasing the number of wells and including multiple periods of QRD, PRD and Type II Luke sequence diffusers. Investigated models showed high frequency dependency of IL and overall gain in average attenuation of 6-8dBA more than a reflective T-barrier. Two-dimensional finite element study was conducted in the acoustic module of COMSOL Multiphysics, while the three-dimensional boundary element study was conducted in SYSNOISE and COMSOL Multiphysics.