  A systematic study of noise barriers based on sonic crystals made of
cylinders that use recycled materials like absorbing component is here
reported. The barriers consist of only three rows of perforated metal shells
filled with rubber crumb. Measurements of reflectance and transmittance by
these barriers are reported. Their attenuation properties result from a
combination of sound absorption by the rubber crumb and reflection by the
periodic distribution of scatterers. It is concluded that porous cylinders can
be used as building blocks whose physical parameters can be optimized in order
to design efficient barriers adapted to different noisy environments.
