Sound Insulation and Reflection Properties of Sonic Crystal Barrier Based on Micro-Perforated Cylinders.

Stefan M Dimitrijević,Víctor M García-Chocano,José Sánchez-Dehesa,Emelie Roth,Francisco Cervera

doi:10.3390/ma12172806

Stefan M Dimitrijević, Víctor M García-Chocano + Show 3 more

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https://doi.org/10.3390/ma12172806

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Abstract

A sonic crystal barrier, consisting of empty micro-perforated cylindrical shells, was built on the campus at the Universitat Politècnica de València in 2011 and characterised by using a non-standardised measurement technique. In this paper, the sonic crystal barrier, upgraded with rubber crumb inside the micro-perforated cylindrical shells, was characterised by using standardised measurement techniques according to EN 1793-5 and EN 1793-6. As a result of the characterisation, sound insulation properties of the barrier were shown to be a combination of the absorptive properties of the individual building units and the reflective properties of their periodic distribution. In addition, its performance was compared with a similar barrier consisting of rigid polyvinyl chloride (PVC) cylinders, which was recently characterised using the same standardised techniques. In comparison with the barrier based on PVC cylinders, the barrier investigated here produced a broadband enhancement of the sound insulation and lower reflection indices in the targeted frequency range. It was also shown that the influence of leakage under the barrier and the width of the temporal window on sound insulation was negligible. While EN 1793-5 and 1793-6 allow a direct comparison of the performance of different noise barriers, the applicability to this new type of barriers requires further investigation.

Highlights

Structures consisting of sound scatterers periodically arranged in a lattice, known as sonic crystals (SCs), have been the subject of many research studies in the last two decades
The sound insulation index (SI) values in the complete band gap are similar to those of SC with polyvinyl chloride (PVC) cylinders, just slightly lower. This is believed to be due to the absorptive nature of the building units, which slightly dampens the effect of the Bragg scattering
SI curves around the complete band gap are wider in case of SC with MP cylinders because of the absorption mechanism introduced by the MP layer, showing a significant difference at low frequencies

Summary

Introduction

Structures consisting of sound scatterers periodically arranged in a lattice, known as sonic crystals (SCs), have been the subject of many research studies in the last two decades. Their ability to prevent sound propagation in certain frequency bands, called band gaps, is their most important characteristic. This is possible due to a mechanism called Bragg scattering, which is the destructive interference between the sound reflected from different scatterers in the lattice. Reported the “state of the art” regarding the different theoretical approaches employed to predict acoustic band gaps in SCs updated up to 1995. It should be noted that references already cited and the ones to come are strictly focused on the application of SCs in developing a new type of acoustic barriers and, the reader is Materials 2019, 12, 2806; doi:10.3390/ma12172806 www.mdpi.com/journal/materials

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