Abstract:

It is proposed that arrays of periodically positioned metallic bars could serve as a low-tech, low-cost, and effective device for filtering out environmental or industrial noise. The proposed scheme is composed of five sets of periodic arrays in tandem, each characterized by a certain value of the period (of square lattice) a and cylinders of radius r; the filling fraction is f=(r2/a2). The purpose of the tandem structure is to achieve an ultra-wideband filter of noise. The tandem structure is designed such that, for certain values of the period, the stop bands of the respective sets of structure superimpose over one another. It is found that, for f=0.55, the tandem structure should shield from noise in the entire range between 2.0 and 11.0 kHz. This is attributed to the formation of a ``super stop band'' due to overlapping of the five individual stop bands. An ultra-wideband filter for environmental or industrial noise could thus be fabricated according to the specific requirements. This idea is based on the band structure calculations reported in the preceding abstract.