SOUND REFLECTION AND SOUND INSULATION MEASUREMENTS ON A SONIC CRYSTAL NOISE BARRIER ACCORDING TO THE NEW EUROPEAN METHODOLOGY

摘要

Noise barriers based on sonic crystals are very promising, being light-weighting and permittinglight and airflow passage. On the other hand, they have unusual sound insulationand sound reflection properties, dominated by multiple scattering phenomena. Theoreticalliterature predicts sound transmission spectra exhibiting stop-band regions, while veryfew considerations have been published on the sound reflection spectra. The main aim ofthis work is to show the applicability of the European standards EN 1793-5 and EN 1793-6(originated from the QUIESST project) to these kind of structures. Measurements weredone on a sample made of hollow PVC cylinders - outer diameter 160 mm - arranged ina square lattice with a height of 3 m and an overall width of 3 m. Its depth varied from1 to 5 rows of cylinders. FEM simulations were performed in order to control and addressthe experimental campaign. Regarding sound insulation, a good matching betweensimulations and measurements was found in the first Bragg band gap, occurring in the800 Hz one-third octave band. Increasing the number of rows, sound insulation increasesas expected. Regarding sound reflections, the study confirms the existence of a stronglyinterferential sound field, as for reflecting non-flat noise barriers.