Chiral composites as underwater acoustic attenuators

The plane wave propagating in effectively chiral composites (ECC) had been asymptotically investigated. The analysis represented the reflected and transmitted phenomena of an incident P-wave from an elastic solid against the effective chiral composite. Consequently, an interesting and potentially important phenomenon from the computations was that the P-, SV-, and SH-waves are coupled together in the reflected field. In general, the ECC can be fabricated by embedding the helical arrangement of microstructures in the soft matrix. Therefore, two nondispersive longitudinal wavenumbers and four dispersive circularly polarized transverse wavenumbers can be found from the dispersion equation. The latter also indicated that two transition frequencies divide the frequency spectrum of the transverse wavenumbers into three different groups and the four transverse modes can only be distinguished in a specified frequency range. In this work, we illustrate the reflected and transmitted fields of an acoustic plane wave propagating at the fluid-chiral interfaces. It is observed that, due to the mode conversion of the chirality in the chiral medium, the chiral material should instigate a reducible reflected plane wave, and may be used as an acoustic attenuator to "absorb" sound in underwater.