Anomalous Transmission Properties of Ultranarrow, Zero-Density Acoustic Metachannels

We present the acoustic equivalent of supercoupling through subwavelength channels. Extraordinary matched transmission, energy squeezing and anomalous quasistatic tunnelling through narrow channels are obtained for acoustic waves by designing a 2D, density-near-zero metachannel. Transmission-line theory is used to describe this peculiar phenomenon, and full-wave simulations are presented to confirm the exotic transmission properties of the metamaterial. It is shown that acoustic waves may provide a unique possibility of squeezing energy in arbitrarily small channels in 3D, overcoming limitations usually arising in the electromagnetic case.