Shape-optimal design of graded index sonic crystal noise barriers with line defects
Paper i proceeding, 2013

A graded index sonic crystal gives rise to upward refraction due to a negative sound speed gradient, which progresses with height. However, in addition to upward refraction, these cylinder formations can simultaneously benefit from band-gap phenomena. This paper presents a method to optimise graded index sonic crystals for broadband traffic noise by: (1) organising cylinders in complex formations using natural cubic splines and (2) introducing line defects. All variables were optimised with a multi-objective genetic algorithm, for structures based on horizontally oriented acoustically hard cylinders, located above a perfectly reflecting ground plane. A four-lane outdoor situation, with a traffic scenario consisting of 95 % light and 5 % heavy vehicles driving at 70 km/h has been studied. For such a configuration we obtained a spatially averaged mean reduction of 3.7, 4.3 and 5.4 dBA, with optimised structures covering an effective cross-sectional area of 0.69, 1.25 and 1.45 m2, respectively. It is found that the focussing performance of the studied structures is enhanced by increasing the number of scatterers as a function of height, which effectively represents a negative sound speed gradient. In addition, it is found that the effect of line defects is significant, and that the insertion loss among the studied traffic lanes is reasonably constant.

Outdoor sound propagation

Graded index sonic crystal

Sonic crystal

Optimisation

Författare

Bart van der Aa

Vibroakustik

Jens Forssén

Vibroakustik

42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013

Vol. 3 2325-2334

Styrkeområden

Transport

Building Futures

Ämneskategorier

Annan samhällsbyggnadsteknik

ISBN

9781632662675