Published online by Cambridge University Press: 12 April 2011
We theoretically examine the propagation of sound in a waveguide bounded by a metamaterial formed by an array of small Helmholtz resonators. The field equation is shown to be similar to that governing sound in a bubbly liquid. The effects of dissipation on the wave dispersion are examined. In particular, it is shown that the energy in a monochromatic wave train is not transported by the real part of the complex group velocity unless dissipation is absent. We further derived the envelope equation and show that in a one-dimensional waveguide, energy is transported forward despite the backward motion of the envelope peak.