Noise control in ducts using local resonator acoustic metamaterial arrays.

Resumo

Acoustic local resonators (Helmholtz, side branch, expansion chamber etc.) are usually used to control
noise in acoustic systems. Noise attenuation in local resonators occurs due to impedance mismatch of incident,
transmitted, and reflected waves induced by the addition of resonators. The frequency band and the attenuation
level generated by the resonator depend on its geometry and behave as a narrow-band filter. However, if they are
distributed properly (periodically or not) along the duct length, a much larger frequency band, called bandgap, is
obtained. In this paper, acoustic metamaterial noise attenuation is investigated using the transfer matrix method and
assuming plane wave propagation. Also, a study about the arrangements of the local resonators (serial and parallel)
is conducted to verify the method accuracy and efficiency related to band width enlargement and transmission loss.
Simulated results are obtained for different examples and geometries.