Optimum control of broadband noise by barriers based on sonic crystals
  It is demonstrated that sonic crystals (periodic structures of sound scatterers) can be used to design acoustic barriers that attenuate efficiently broadband noise. Traffic noise is chosen here as an example in which our design procedure is applied. The structures consist of cylindrical units containing rubber crumb, a sound absorbing material. An optimization algorithm is developed to obtain the material distribution and the dimensions of the sonic crystal giving the best attenuation properties for this noise. The good agreement found between predictions and measurements for a barrier (3m height) characterized in a transmission room gives strong support to our proposal. 
Victor Manuel Garc\'ia-Chocano and Jos\'e S\'anchez-Dehesa
cond-mat.mtrl-sci