Insertion loss of periodic cylindrical shells with helical slit

Abstract

We propose periodic shells with helical slit to overcome the lacuna in periodic C scatterers, where the first Bragg band is considerably reduced on increasing width of the slit. The key discovery of this research indicates that, by changing the upright slit of the C scatterers to helical slits, larger insertion loss (IL) is achieved around the first Bragg band without compromising the local resonance band. Comparing the performance of periodic shells without slit or cylindrical scatterers, it is found that IL becomes larger at first Bragg band. The pitch, thickness of the shell and width of helical slit can be altered to adjust the resonance of the proposed shells. On decreasing the pitch or increasing the slit width, the resonance band shifts toward high frequencies without much alteration in acoustic attenuation of bandwidth. Additionally, below threshold pitch, the said peak merges with first Bragg band and broadens with prominent IL. The calculated band structure authenticates the bandwidth of the first Bragg band, and the additional sharp peak in IL can be attributed to local resonance of the periodic scatterers.

Numerical and experimental methods to measure the acoustic performance of sonic crystal noise barrier

“…It has been observed that the IL of C-shaped scatterers is dependent on the orientation of the vertical slit opening of the scatterers. 25,26 Unlike, C-shaped scatterers, the IL of periodic cylindrical scatterers is independent orientation of the scatterers. The detailed observations with IL for the periodic cylindrical and C-shaped scatterers.…”

“…For the reference, other experimental studies also have been performed using portable anechoic chamber. [26][27][28] (b) The sound pressure has been measured with PCB© free field array microphone. The calibration of the microphone has been carried out with an L&D© class one calibrator with (model no CAL-200©).…”

“…For the reference, other experimental studies also have been performed using portable anechoic chamber. 26–28…”